Article # 1:
Evan Shane Williams and William R. Wise, Hydrologic Impacts of Alternative Approaches to Storm Water Management and Land Development, April 2006, Journal of the American Water Resource Association
Summary:
The paper discusses of the hydrologic impacts caused by different alternatives of storm management and land development options. The study is carried out based on the alternatives considering the traditional and clustered development along with LID technique and with the LID technique. Along with these alternatives they studied how the hydrology is affected with connected (runoff from impervious cover being discharged into the conveyance system directly without any infiltration i.e. implying no vertical storage) and disconnected impervious cover (allowing infiltration i.e. rooftop runoff discharged into lawns and roads draining to swales). These alternatives were compared with the existing conditions i.e. without any land development. They have used different metrics to compare the effects of runoff – peak flow, flow duration, time to peak, and runoff volume. The paper focuses on the possible areas of hydrologic concerns with different land developments and storm management practices.
Article # 2:
E. Downey Brill, JR. John M. Flach, Lewis D. Hopkins, S. Ranjithan, MGA: A Decision Support System for Complex Incompletely Defined Problems, August 1990
Summary:
The paper focuses on how the infiltration types effect could be different depending on the type of land development. The study carried out evaluates combinations of different infiltration practices (i.e spread roof to lawn, rain garden, reduction on street width, green swales etc) and they have even carried out comparative analysis of different soil groups with these mentioned infiltration practices. The research proves that the land development which leaves most of the land unaltered i.e. leaving it in natural condition are the ones which have less effects on the urban runoff. With the strategic combinations of land development and corresponding infiltration practices it would be possible to deal with the hydrologic impacts caused due to the increased runoff.
Article # 3:
David J Sample, James P Heaney, Integrated Management of Irrigation and Urban Storm Water Infiltration, October 2006, Journal of Water Resource Planning and Management
Summary:
The paper focuses on integrating the water conservation, irrigation management planning and storm management for a study area of a subdivision in Boulder, Colorado. Paper illustrates different studies carried out in integrating the storm water and usage of LID techniques which has received recent attention in the research community. According to the studies carried out LID is considered to be better mimic of the pre development conditions and LID relies in managing the runoff at the site thereby reducing the directly connected impervious area (DCIA) thereby reducing the storm runoff produced. DCIA runoff as is collected by the storm conveyance system which have the potential of being transported away from the irrigation users, therefore for in-site storm management we need concentrate on the non-DCIA and pervious areas. They have carried out different options of irrigation management plans and studied the water budget of the area. Cost comparison was carried out between these options. They have carried out study to find out the optimal rain water storage volume to result in highest net benefits, it was found to be for the capacity of 10000L that results in highest net benefit. Author concludes about how the most benefited (Net benefit) option is associated with conserving the water (storing in cisterns) for the irrigation options.
Article # 4:
Kristin L Gilroy, Richard H McCuen, Spatio-temporal effects of low impact development practices, 2009, Journal of hydrology
Summary:
The paper focuses the importance of the factors like optimal location, quantity of BMP and land use types which needs to be investigated to achieve the optimal effectiveness of the LID’s being used for the storm water management. The paper covers the study carried out on a spatio-temporal micro watershed which is used to study the effectiveness of BMP with respect to the location and the volume. In the study they have considered bio retention and cisterns to deal with the increased peak discharge and runoff volume. Bio retention was used majorly as the infiltration where as cisterns was above surface storage which is used to manage the runoff from the rooftop. The authors have carried out the study considering different land use patterns and modeled using 2 different storm events 1 yr and 2 yr. They have studied the effectiveness of each of the BMP used with respect to these scenarios. For the comparison of the results they have considered two metrics i.e. peak flow and runoff volume to measure the effectiveness of the scenarios and BMP used.
Article # 5:
Q. Xiao, E G McPherson, J R Simpson and S L Ustin, Hydrologic processes at the urban residential scale, October 2006
Summary:
The paper focuses on building up a physical numerical model to understand hydrologic processes in the urban scale and its interaction with different BMP’s. The model was applied to a single family residential lot in Los Angeles, CA. Model was calibrated and validated by the data collected for over 2 yrs. They have modeled rain gutters, driveway interceptors and lawn retention basin. It was observed that there was about 65% reduction in storm water by using driveway interceptor. But using the rainwater gutters the annual irrigation demand was provided by 9%. It was observed that all the BMP’s installed in the treatment site were effective in reducing the storm runoff and reducing the irrigation demand from the municipal water demand. Using these strategies enabled the improvement of urban eco system. BMP has reduced the maximum runoff flow to the streets and the maximum annual evaporation and increased the deep percolation. Increased percolation increases the downstream base flow and groundwater recharge. For runoff reduction driveway interceptor and drywell combination was the best but this BMP carries the risk of carrying pollutants from the surface runoff into the ground water. Cistern provided additional irrigation demand supply but for more effective use of cistern it should be appropriately designed for the catchment areas. Few of the sites will not follow the sub surface balance which focuses on the importance of more detailed model with such kind of topographic situations.
Article # 6:
Wolfram Schluter, Chris Jefferies, Modeling the outflow from a porous pavement, October 2001
Summary:
This paper focuses on modeling a 20 month old porous pavement in Edinburgh which was calibrated using 15 storm events. Storm water software package Erwin is used to simulate the outflow from these porous pavements. 16 events were recorded out of which one was recorded using the flow logger where as the rest were recorded with the V notch weir located at the outlet of the monitoring manhole. The porous pavement does not drain total inflow but it retains a certain amount which would be evaporated unless a future precipitation occurs. From the conclusion which they observed after running the simulation model for both single event and long term simulation is that the wetness of the porous pavement prior to the event will increase the outflow of the following event. Therefore studying the simulation for long term would be more advisable as it takes into consideration the wetness of the porous pavement. The study observed that Porosity of the filling material under the porous pavement has a little influence on the volume of the runoff but has an impact on the peak flow rate.
Article # 7:
James. W, James W.R.C, Von Langsdorff H, Computer Aided design of permeable concrete block pavement for reducing stressors and contaminants in an urban environment, October 2003
Summary:
This paper focuses on illustrating the new component which is linked up to EPA SWMM which is used to model the permeable pavements called as PCSWMM. The paper gives illustration of all the different components in the PCSWMM. Permeable pavement depends on design of storage capacity (which can store the storm water) and surface infiltration rate. PCSWMM addresses hydraulic and hydrologic aspects of permeable pavement. Two main concerns addressed by the software is the maximum depth of water that can be stored for the designed storm and the time taken to drain from the base layer of the pavement. This interface calculates the flow of runoff through different layers of the pavements i.e. pavers, base layer, and subgrade. The paper did not cover any examples of using this software. The authors mentioned about the groundwater and infiltration calculations need to be tested or verified.
Friday, August 28, 2009
Monday, August 3, 2009
Discussion # 6 (03 Aug 2009) : Common Paper
Article Reference
Zoong Woo Geem, Harmony search optimization to the pump included water distributed network design, Environmental Planning and management program, Sept 2009
Introduction
The paper focuses the optimization of the water distribution system along with the pumps which have not been included in the literature of hydrosystems optimization. Optimal solution obtained by the mathematical model is in terms of continuous pipe diameters and in the means of converting those to available commercial diameters might alter the quality of the solution. However meta heuristic optimization techniques like GA, tabu search etc have been used in optimizing distribution network , these algorithms resulted more discrete pipe diameters than the continuous diameters. This paper focuses applying harmony search in optimizing the cost of the water distribution system including the pumps.
Objective function: design cost function
Decision variable: pipe diameters or pump size
HS model most used parameters range: HM range 30-100, HMCR – 0.95-0.99, PAR – 0.05-0.2
Steps followed in HS method are:
1. Initialization of the HM by selecting the vectors randomly
2. Improvisation of the HM by random selection (randomly selecting the decision variable from HM), memory consideration (using the HMCR the next step HM would be choosen), Pitch adjustment (adjusting the pitch i.e selecting the neighboring value based on the given probability) and violated harmony consideration (the new HM is checked by hydraulic analysis to check the nodal pressure, if the nodal pressures are greater than the limit then penalty is added to the design cost)
3. New HM is replaced by the previous HM if the new HM is a better solution than the old HM
4. Stopping criteria is specified by maximum iterations, so the steps 2 and 3 are continued till it reached the maximum iterations
Problem formulation
• Objective function: Pipe capital cost + pump capital cost + pumping energy cost
• Penalty function: squared penalty value + constant penalty value, if the pressure at the nodes do not meet the minimum criteria
• This penalty function is added to the cost objective function
Model
• 10 commercial diameters considered
• L = 2500 m
• 9 commercial pump sizes considered
• Water demand specified at each node
• Minimum pressure at each node should be 30 m above GL
• No. of pipes = 11
• No. of nodes = 9
Conclusions and Discussion
This research explains using meta heuristic technique in distribution optimization along with four different search behaviors. The same problem was solved using Simulated annealing and the cost was identical to that of HS. However HS produced much lower average cost and within less number of function evaluations.
Zoong Woo Geem, Harmony search optimization to the pump included water distributed network design, Environmental Planning and management program, Sept 2009
Introduction
The paper focuses the optimization of the water distribution system along with the pumps which have not been included in the literature of hydrosystems optimization. Optimal solution obtained by the mathematical model is in terms of continuous pipe diameters and in the means of converting those to available commercial diameters might alter the quality of the solution. However meta heuristic optimization techniques like GA, tabu search etc have been used in optimizing distribution network , these algorithms resulted more discrete pipe diameters than the continuous diameters. This paper focuses applying harmony search in optimizing the cost of the water distribution system including the pumps.
Objective function: design cost function
Decision variable: pipe diameters or pump size
HS model most used parameters range: HM range 30-100, HMCR – 0.95-0.99, PAR – 0.05-0.2
Steps followed in HS method are:
1. Initialization of the HM by selecting the vectors randomly
2. Improvisation of the HM by random selection (randomly selecting the decision variable from HM), memory consideration (using the HMCR the next step HM would be choosen), Pitch adjustment (adjusting the pitch i.e selecting the neighboring value based on the given probability) and violated harmony consideration (the new HM is checked by hydraulic analysis to check the nodal pressure, if the nodal pressures are greater than the limit then penalty is added to the design cost)
3. New HM is replaced by the previous HM if the new HM is a better solution than the old HM
4. Stopping criteria is specified by maximum iterations, so the steps 2 and 3 are continued till it reached the maximum iterations
Problem formulation
• Objective function: Pipe capital cost + pump capital cost + pumping energy cost
• Penalty function: squared penalty value + constant penalty value, if the pressure at the nodes do not meet the minimum criteria
• This penalty function is added to the cost objective function
Model
• 10 commercial diameters considered
• L = 2500 m
• 9 commercial pump sizes considered
• Water demand specified at each node
• Minimum pressure at each node should be 30 m above GL
• No. of pipes = 11
• No. of nodes = 9
Conclusions and Discussion
This research explains using meta heuristic technique in distribution optimization along with four different search behaviors. The same problem was solved using Simulated annealing and the cost was identical to that of HS. However HS produced much lower average cost and within less number of function evaluations.
Friday, July 31, 2009
Discussion # 5 (22 July 2009) : Common Paper
Article Reference
Zoong Woo Geem, Joong Hoon Kim, G V Loganathan, A New heuristic Optimization Algorithm : Harmony Search
Introduction
The paper tries to focus on the new heuristic algorithm called “Harmony Search” (HS) which is explained using three examples – TSP, academic optimization problem and a least cost pipe network design problem. Authors explain the drawbacks of using the normal optimization methods i.e LP, NLP and DP. In LP there are considerable losses associated as the real world non linear model is being expressed as a linear model; In DP increased variable increase the evaluation of the recursive functions; in NLP if the functions are not differentiable then finding optimum is not possible and attention is required to select the initial values in order to guarantee global optima instead of local optima. To overcome the above mentioned drawbacks, heuristic method of optimization is developed which results in near optimum solution within reasonable computation time and within reasonable use of memory. Since 1970 there have been many heuristic algorithms which have been developed combining rules and randomness mimicking the natural processes. The techniques are:
• Simulated annealing (SA) – It is based on the analogy of physical annealing process. In physical annealing as the materials temperature increases the molecules mobility increases and gradually these molecules form the crystalline structure i.e. the optimal solution.
• Tabu search (TS) – it explores the search space of feasible solutions by sequence of moves. To escape from the local optima and to prevent cycling some moves are classified as tabu.
• Evolutionary algorithms (EA) – it is based on the principle of evolution. Consists of four heuristic algorithms- genetic algorithm, evolutionary strategies, evolutionary programming and genetic programming.
• Genetic Algorithm – based on the natural selection and the mechanism of population genetics. It has three operators – reproduction, crossover and mutation. Main advantage of GA when compared to other optimization techniques or heuristic techniques is that GA evaluates different solutions simultaneously unlike the other methods which evaluate on solution at a time.
• Evolutionary strategies
• Evolutionary programming
• Genetic programming
These simulation based heuristic search techniques have powerful search abilities which overcome the drawbacks of the traditional optimization techniques. The paper proposes a new heuristic search technique which produces better solution in less number of iterations than the other techniques.
New Heuristic technique (Harmony Search)
The steps to be followed in this new technique are:
• Step 1 – Initialize a Harmony memory (HM)
• Step 2 – Improvise a new harmony from HM
• Step 3 – If the new harmony is better than the minimum harmony in HM then include the new harmony in the HM and exclude the minimum harmony from HM
• Step 4 – if the stopping criteria are not met then repeat the Step 2.
To improve the solutions and escaping from the local optima there two methods which are introduced, they are:
• Harmony memory considering rate (HMCR): indicates the probability of the algorithm which selects the variable from the harmony memory onto the next step
• Pitch adjusting rate (PAR): shifting the values to nearby neighboring values in the specified range which is called as PAR. PAR 10% means the new value is selected in the probability of 10% (5% of higher value or lower value with 5%)
Major difference between HS and GA is that HS makes a new vector from the existing vectors (i.e from all harmonies in the Harmony memory) where as GA makes new vector only from the two existing vectors (parent).
Examples
1. Travel Salesman Problem – Harmony memory consists of the existing tour lengths, if the new tour length is shorter than the existing HM tour lengths then the new tour length is replaced in the HM. Different HMCR and PAR parameters are considered and the iterations are performed to avoid the local optima solution. For faster convergence two new operators have been introduced – Neighboring city (i.e salesman visiting the closest neighboring city) and city inverting (i.e inverting the city if the former is shorter than the later city).
2. Simple constrained minimization problem – Initially decision variable x1 and x2 have been selected randomly based on the given range later the range has been narrowed to the values in the HM. This problem was solved using generalized reduced gradient (GRG), EP and GA, HS has evolved much better solutions than the other methods.
3. Design of pipe network for water supply – The problem has 32 nodes, 32 links and 3 loops, no pumping station is considered. Minimum pressure requirement at all the nodes is specified. This problem was solved using Nonlinear programming gradient and GA. HS gave a minimum least cost of the pipe network when compared to the other heuristic methods.
Conclusions and Discussion
HS is advantageous than the other methods
- as it makes a new set of vectors based on all existing vectors instead of just two vectors (parent),
- it does not require initial values of the decision variables
- It outperformed the other heuristic techniques (GA, EP etc)
- Faster convergence
Zoong Woo Geem, Joong Hoon Kim, G V Loganathan, A New heuristic Optimization Algorithm : Harmony Search
Introduction
The paper tries to focus on the new heuristic algorithm called “Harmony Search” (HS) which is explained using three examples – TSP, academic optimization problem and a least cost pipe network design problem. Authors explain the drawbacks of using the normal optimization methods i.e LP, NLP and DP. In LP there are considerable losses associated as the real world non linear model is being expressed as a linear model; In DP increased variable increase the evaluation of the recursive functions; in NLP if the functions are not differentiable then finding optimum is not possible and attention is required to select the initial values in order to guarantee global optima instead of local optima. To overcome the above mentioned drawbacks, heuristic method of optimization is developed which results in near optimum solution within reasonable computation time and within reasonable use of memory. Since 1970 there have been many heuristic algorithms which have been developed combining rules and randomness mimicking the natural processes. The techniques are:
• Simulated annealing (SA) – It is based on the analogy of physical annealing process. In physical annealing as the materials temperature increases the molecules mobility increases and gradually these molecules form the crystalline structure i.e. the optimal solution.
• Tabu search (TS) – it explores the search space of feasible solutions by sequence of moves. To escape from the local optima and to prevent cycling some moves are classified as tabu.
• Evolutionary algorithms (EA) – it is based on the principle of evolution. Consists of four heuristic algorithms- genetic algorithm, evolutionary strategies, evolutionary programming and genetic programming.
• Genetic Algorithm – based on the natural selection and the mechanism of population genetics. It has three operators – reproduction, crossover and mutation. Main advantage of GA when compared to other optimization techniques or heuristic techniques is that GA evaluates different solutions simultaneously unlike the other methods which evaluate on solution at a time.
• Evolutionary strategies
• Evolutionary programming
• Genetic programming
These simulation based heuristic search techniques have powerful search abilities which overcome the drawbacks of the traditional optimization techniques. The paper proposes a new heuristic search technique which produces better solution in less number of iterations than the other techniques.
New Heuristic technique (Harmony Search)
The steps to be followed in this new technique are:
• Step 1 – Initialize a Harmony memory (HM)
• Step 2 – Improvise a new harmony from HM
• Step 3 – If the new harmony is better than the minimum harmony in HM then include the new harmony in the HM and exclude the minimum harmony from HM
• Step 4 – if the stopping criteria are not met then repeat the Step 2.
To improve the solutions and escaping from the local optima there two methods which are introduced, they are:
• Harmony memory considering rate (HMCR): indicates the probability of the algorithm which selects the variable from the harmony memory onto the next step
• Pitch adjusting rate (PAR): shifting the values to nearby neighboring values in the specified range which is called as PAR. PAR 10% means the new value is selected in the probability of 10% (5% of higher value or lower value with 5%)
Major difference between HS and GA is that HS makes a new vector from the existing vectors (i.e from all harmonies in the Harmony memory) where as GA makes new vector only from the two existing vectors (parent).
Examples
1. Travel Salesman Problem – Harmony memory consists of the existing tour lengths, if the new tour length is shorter than the existing HM tour lengths then the new tour length is replaced in the HM. Different HMCR and PAR parameters are considered and the iterations are performed to avoid the local optima solution. For faster convergence two new operators have been introduced – Neighboring city (i.e salesman visiting the closest neighboring city) and city inverting (i.e inverting the city if the former is shorter than the later city).
2. Simple constrained minimization problem – Initially decision variable x1 and x2 have been selected randomly based on the given range later the range has been narrowed to the values in the HM. This problem was solved using generalized reduced gradient (GRG), EP and GA, HS has evolved much better solutions than the other methods.
3. Design of pipe network for water supply – The problem has 32 nodes, 32 links and 3 loops, no pumping station is considered. Minimum pressure requirement at all the nodes is specified. This problem was solved using Nonlinear programming gradient and GA. HS gave a minimum least cost of the pipe network when compared to the other heuristic methods.
Conclusions and Discussion
HS is advantageous than the other methods
- as it makes a new set of vectors based on all existing vectors instead of just two vectors (parent),
- it does not require initial values of the decision variables
- It outperformed the other heuristic techniques (GA, EP etc)
- Faster convergence
Discussion # 5 (22 July 2009)
Article Reference
Q. Xiao, E G McPherson, J R Simpson and S L Ustin, Hydrologic processes at the urban residential scale, October 2006
Introduction
The paper focuses on building up a physical numerical model to understand hydrologic processes in the urban scale and its interaction with different BMP’s. The model was applied to a single family residential lot in Los Angeles, CA. Model was calibrated and validated by the data collected for over 2 yrs. They have modeled rain gutters, driveway interceptors and lawn retention basin. It was observed that there was about 65% reduction in storm water by using driveway interceptor. But using the rainwater gutters the annual irrigation demand was provided by 9%. They modeled trying to replace the existing loam soil with clay soil and it was observed that annual runoff discharge to the street was increased by 63%. In this study they have considered the case study of Los Angeles which has the polluted runoff being flown into local watershed and thereby into the coastal recreation areas. LA experience sever summer deficit of water demand where they import almost 85% of the water to meet their demands. Author focuses on how the policy makes are considering the implementation of the decentralized approach in the urban watershed i.e creating a mini reservoir system which retains runoff and reducing the irrigation demand but they lack the quantitative data on the effectiveness of the usage of different BMP’s. Most of the urban hydrologic models focus on the water balance and not on the effects on the BMP’s on the hydrologic processes which are dependent on the land use.
Objective of the study:
Develop, calibrate and validate the physical model at the residential scale for simulating the runoff for both long term events and storm term storm events. The study is carried out to see the effectiveness of BMP and simulating the effects of retrofitting the control site with the BMP’s.
Methodology:
• Site: residential housing unit
• BMP’s considered: cistern, swale, rain gutter, lawn retention basin, driveway interceptor and drywell
• Designed for 50 yr storm event
• Runoff from rooftops flowed into cistern and lawn retention basin
• Runoff from driveway flowed into the interceptor and further into the drywell
The data was collected from Jan 2001 to Jan 2003 and the model was calibrated and modeled based on the measurements of land covers, hydrologic processes and micro climate data. The runoff from treatment Site Street was collected in the measurement system and then through the water outlet drainages where as the runoff from the control site was drained directly into the drive way and thereby into the street. Each land cover was considered as a individual modeling unit. The model was studied for both long term simulation and short term events. For the long term simulation the focus of study was taking into consideration the annual irrigation use and runoff to the street and for short term simulation the focus was on the storm runoff to the street and the storage of the BMP.
• Precipitation data taken as the input of the rainfall data
• Two strategies of irrigation (first using the annual ET and second one was based on the soil and water deficit) were used in the model to determine the timing and the amount of water to be applied.
• Interception losses are also taking into consideration in the model
• Surface flow is calculated using the manning’s equation
• Infiltration is estimated using Green Ampt’s equation
• Percolation
• Evapo-transpiration
• Lateral subsurface flow
• Cistern storage is based on the total amount of water entering the cistern and the cistern restricted area
Numerical simulation focused on the landscape irrigation, storm runoff, ET and percolationof runoff into the deep layers, sensitivity analysis of the landscape retrofit was simulated using the date of 2001 and the 50 yr storm event (1988). The purpose of the sensitivity analysis was to distinguish which BMP was more effective with respect to runoff reduction and conservation of landscape irrigation water use. For the control site there were not BMP retrofitted which was considered as the base condition and the treatment site was varied with 6 different BMP’s. Other type of sensitivity analysis was carried by replacing with the clay soil instead of sandy soil.
Results:
Both treatment site and control site had about 50% impervious cover. Field measurement revealed that both cistern and retention basin were more effective in conserving municipal water supplies and reducing the total storm runoff. Surface runoff was effectively reduced by the drive way interceptors and lawn retention basin.
Discussion:
It was observed that all the BMP’s installed in the treatment site were effective in reducing the storm runoff and reducing the irrigation demand from the municipal water demand. Using this strategies enabled the improvement of urban eco system. BMP has reduced the maximum runoff flow to the streets and the maximum annual evaporation and increased the deep percolation. Increased percolation increases the downstream base flow and groundwater recharge. For runoff reduction driveway interceptor and drywell combination was the best but this BMP carries the risk of carrying pollutants from the surface runoff into the ground water. Cistern provided additional irrigation demand supply but for more effective use of cistern it should be appropriately designed for the catchment areas. Few of the sites will not follow the sub surface balance which focuses on the importance of more detailed model with such kind of topographic situations.
Conclusions
• Most effective BMP is driveway interceptor
• Cistern provided 9% of the annual irrigation demand
• Annual irrigation demand was reduced by 53% by adjusting the irrigation efficiency and application rates based on the plant water demand
• Simulation studies concluded that infiltration and surface runoff is the function of the soil properties and its effective depth
• Selection of the BMP is based on testing the soil properties
Q. Xiao, E G McPherson, J R Simpson and S L Ustin, Hydrologic processes at the urban residential scale, October 2006
Introduction
The paper focuses on building up a physical numerical model to understand hydrologic processes in the urban scale and its interaction with different BMP’s. The model was applied to a single family residential lot in Los Angeles, CA. Model was calibrated and validated by the data collected for over 2 yrs. They have modeled rain gutters, driveway interceptors and lawn retention basin. It was observed that there was about 65% reduction in storm water by using driveway interceptor. But using the rainwater gutters the annual irrigation demand was provided by 9%. They modeled trying to replace the existing loam soil with clay soil and it was observed that annual runoff discharge to the street was increased by 63%. In this study they have considered the case study of Los Angeles which has the polluted runoff being flown into local watershed and thereby into the coastal recreation areas. LA experience sever summer deficit of water demand where they import almost 85% of the water to meet their demands. Author focuses on how the policy makes are considering the implementation of the decentralized approach in the urban watershed i.e creating a mini reservoir system which retains runoff and reducing the irrigation demand but they lack the quantitative data on the effectiveness of the usage of different BMP’s. Most of the urban hydrologic models focus on the water balance and not on the effects on the BMP’s on the hydrologic processes which are dependent on the land use.
Objective of the study:
Develop, calibrate and validate the physical model at the residential scale for simulating the runoff for both long term events and storm term storm events. The study is carried out to see the effectiveness of BMP and simulating the effects of retrofitting the control site with the BMP’s.
Methodology:
• Site: residential housing unit
• BMP’s considered: cistern, swale, rain gutter, lawn retention basin, driveway interceptor and drywell
• Designed for 50 yr storm event
• Runoff from rooftops flowed into cistern and lawn retention basin
• Runoff from driveway flowed into the interceptor and further into the drywell
The data was collected from Jan 2001 to Jan 2003 and the model was calibrated and modeled based on the measurements of land covers, hydrologic processes and micro climate data. The runoff from treatment Site Street was collected in the measurement system and then through the water outlet drainages where as the runoff from the control site was drained directly into the drive way and thereby into the street. Each land cover was considered as a individual modeling unit. The model was studied for both long term simulation and short term events. For the long term simulation the focus of study was taking into consideration the annual irrigation use and runoff to the street and for short term simulation the focus was on the storm runoff to the street and the storage of the BMP.
• Precipitation data taken as the input of the rainfall data
• Two strategies of irrigation (first using the annual ET and second one was based on the soil and water deficit) were used in the model to determine the timing and the amount of water to be applied.
• Interception losses are also taking into consideration in the model
• Surface flow is calculated using the manning’s equation
• Infiltration is estimated using Green Ampt’s equation
• Percolation
• Evapo-transpiration
• Lateral subsurface flow
• Cistern storage is based on the total amount of water entering the cistern and the cistern restricted area
Numerical simulation focused on the landscape irrigation, storm runoff, ET and percolationof runoff into the deep layers, sensitivity analysis of the landscape retrofit was simulated using the date of 2001 and the 50 yr storm event (1988). The purpose of the sensitivity analysis was to distinguish which BMP was more effective with respect to runoff reduction and conservation of landscape irrigation water use. For the control site there were not BMP retrofitted which was considered as the base condition and the treatment site was varied with 6 different BMP’s. Other type of sensitivity analysis was carried by replacing with the clay soil instead of sandy soil.
Results:
Both treatment site and control site had about 50% impervious cover. Field measurement revealed that both cistern and retention basin were more effective in conserving municipal water supplies and reducing the total storm runoff. Surface runoff was effectively reduced by the drive way interceptors and lawn retention basin.
Discussion:
It was observed that all the BMP’s installed in the treatment site were effective in reducing the storm runoff and reducing the irrigation demand from the municipal water demand. Using this strategies enabled the improvement of urban eco system. BMP has reduced the maximum runoff flow to the streets and the maximum annual evaporation and increased the deep percolation. Increased percolation increases the downstream base flow and groundwater recharge. For runoff reduction driveway interceptor and drywell combination was the best but this BMP carries the risk of carrying pollutants from the surface runoff into the ground water. Cistern provided additional irrigation demand supply but for more effective use of cistern it should be appropriately designed for the catchment areas. Few of the sites will not follow the sub surface balance which focuses on the importance of more detailed model with such kind of topographic situations.
Conclusions
• Most effective BMP is driveway interceptor
• Cistern provided 9% of the annual irrigation demand
• Annual irrigation demand was reduced by 53% by adjusting the irrigation efficiency and application rates based on the plant water demand
• Simulation studies concluded that infiltration and surface runoff is the function of the soil properties and its effective depth
• Selection of the BMP is based on testing the soil properties
Friday, July 10, 2009
Discussion # 4 (10 July 2009)
Article Reference:
Kristin L Gilroy, Richard H McCuen, Spatio-temporatl effects of low impact development practices, 2009, Journal of hydrology
Introduction:
Many hydrologists are taking up the option of Best Management practices which is majorly coz of their cost effectiveness. As it is known that with the increase of urbanization, impervious surface increases which prevents water from infiltrating. This prevention of infiltration reduces the ground water recharge, lowers the water table, increasing the surface runoff and reducing the base flow during the dry periods. These add to degrading the stream channels and increasing the transport of pollutants. With storm management plans like detention pond, wet pond and infiltration basin which though they reduce the downstream peak discharge, issue of increased runoff into the stream continue which harms the aquatic life in the stream. Author points out as to the dependency of finding out the factors like optimal location, quantity of BMP and land use types needs to be investigated to achieve the optimal effectiveness of the LID’s. According to study carried out by Schneider et.al (2006) cisterns have showed to be more effective for the small storms when compared to large storms. Various studies concluded that infiltration technique is beneficial depending on the soil texture and the rainfall event size. According to Brander et. Al (2004) using numerous infiltration technique is more effective than few conventional practices with equivalent volume. Hood et. Al (2007) carried out the comparative study with LID development and traditional development which showed that the peak discharge, runoff volume and lag time is reduced and especially for smaller storms and shorter durations. The paper covers the study carried out on a spatio-temporal micro watershed which is used to study the effectiveness of BMP with respect to the location and the volume.
Methodology:
Spatial Temporal micro watershed model was developed in Matlab taking into consideration both spatial and temporal characteristics of rainfall and runoff processes of any return period on the lot sized watershed. The study was carried out for 1 yr (2.2 cm) and 2 yr (3.6 cm) events and for 4 watershed layouts (i.e. forested and three varying development patterns – townhome with 35% impervious land, residential with 32.5% impervious cover, and commercial land use with 72% impervious cover). In the study they have considered bio retention and cisterns to deal with the increased peak discharge and runoff volume. Bio retention was used majorly as the infiltration where as cisterns was above surface storage which is used to manage the runoff from the rooftop. From the long term precipitation records in Middle Atlantic region 50% of the storm events are 2 yr or less and of 1 hr duration.
Each lot was assumed to be of 0.1 ha. The model created grids of 20 x 12 cells. For the residential and townhome development, runoff from the roadways is directed onto the grass. Surface runoff of each cell is calculated differently which contained bio retention facility and with cisterns. Cisterns are used only to intercept the rooftop runoff. Outflow from the cistern is drained through the orifice. Once the storage of the cistern is reached, the outflow occurs through the cistern. In the bio retention cells once the depth of the stored water exceeds the storage it overflow where the overflow is equal to total volume of water in storage minus the maximum storage capacity of the facility and this is directed to the down gradient cell.
Results:
Onsite effects on the development
The comparison was made between the type of land pattern (forest, residential, townhome, and commercial) with respect to the two hydrologic metrics i.e. peak discharge and the total volume. It was observed that 1 yr storm was totally infiltrated in the forest pattern i.e. pre development condition. The development patterns have reduced the infiltration potential by increasing the impervious cover.
Effectiveness of cisterns
Effectiveness of cisterns was studied by analyzing the different land patterns with 1 and 2 yr storm events. It was observed that cisterns were more effective with smaller storm, there was about 30% reduction of peak discharge for single family lot for 1 yr storm where as it was only 10% reduction for 2 yr rainfall. If cistern is the only type of BMP in the site then they are ineffective for 2 yr storm, where as they provide some control for smaller events. Volume of cistern should be based on the volume of the runoff at the time of maximum rainfall intensity.
Effectiveness of bio retention location
For the study they have considered the location of bio retention near the cistern overflow, around the outlet of the micro watershed, along the roadway in residential/townhome lot and along the parking lot in commercial lot. There was effective reduction in the runoff volume when bio retention intercepted the roadway runoff and cisterns intercepted the rooftop runoff. But considering the bio retention at the overflow of the cisterns was more effective in reducing the peak discharge, as cisterns storage is reached before the highest storm intensity with bio retention facility there would be storage to control the peak. Location and volume of BMP is dependent on the time of distribution of the rainfall event. Location of bioretention did not make much of a reduction in the total runoff volume as the impervious land cover was greater when compared to the bio retention storage. Whereas peak discharge was decreased with the cisterns storing the runoff and overflow from the cisterns was drained to bio retention facilities.
Effect of storage volume
It was observed that effect of storage volume depends majorly on the land use type. For 1 yr storm event for commercial lot, it was noticed that when the facilities were doubled the peak discharge was reduced by 10% and volume to 30%. Author makes an observation that number of additional facilities is dependent on each watershed which might improve the hydrology.
Varying effects on hydrologic metrics
The two metrics considered to measure the effectiveness of the LID are peak discharge and total runoff volume. Effect of changing the volume of the storage on these two metrics vary as runoff volume can be controlled with the increased storage
Discussion:
I personally found this article interesting as they have tried to check the effectiveness of the LID’s considered, which would be similar to what I am trying to do in my thesis. Check the effectiveness of the RHS and PP in improving the hydrologic condition of the study area. This paper would be helpful when I take up the option of optimizing the location of the LID’s I am considering. For my thesis I would like to measure the two metrics they have mentioned and use Marcio’s HFR metric to analyze the impacts.
Kristin L Gilroy, Richard H McCuen, Spatio-temporatl effects of low impact development practices, 2009, Journal of hydrology
Introduction:
Many hydrologists are taking up the option of Best Management practices which is majorly coz of their cost effectiveness. As it is known that with the increase of urbanization, impervious surface increases which prevents water from infiltrating. This prevention of infiltration reduces the ground water recharge, lowers the water table, increasing the surface runoff and reducing the base flow during the dry periods. These add to degrading the stream channels and increasing the transport of pollutants. With storm management plans like detention pond, wet pond and infiltration basin which though they reduce the downstream peak discharge, issue of increased runoff into the stream continue which harms the aquatic life in the stream. Author points out as to the dependency of finding out the factors like optimal location, quantity of BMP and land use types needs to be investigated to achieve the optimal effectiveness of the LID’s. According to study carried out by Schneider et.al (2006) cisterns have showed to be more effective for the small storms when compared to large storms. Various studies concluded that infiltration technique is beneficial depending on the soil texture and the rainfall event size. According to Brander et. Al (2004) using numerous infiltration technique is more effective than few conventional practices with equivalent volume. Hood et. Al (2007) carried out the comparative study with LID development and traditional development which showed that the peak discharge, runoff volume and lag time is reduced and especially for smaller storms and shorter durations. The paper covers the study carried out on a spatio-temporal micro watershed which is used to study the effectiveness of BMP with respect to the location and the volume.
Methodology:
Spatial Temporal micro watershed model was developed in Matlab taking into consideration both spatial and temporal characteristics of rainfall and runoff processes of any return period on the lot sized watershed. The study was carried out for 1 yr (2.2 cm) and 2 yr (3.6 cm) events and for 4 watershed layouts (i.e. forested and three varying development patterns – townhome with 35% impervious land, residential with 32.5% impervious cover, and commercial land use with 72% impervious cover). In the study they have considered bio retention and cisterns to deal with the increased peak discharge and runoff volume. Bio retention was used majorly as the infiltration where as cisterns was above surface storage which is used to manage the runoff from the rooftop. From the long term precipitation records in Middle Atlantic region 50% of the storm events are 2 yr or less and of 1 hr duration.
Each lot was assumed to be of 0.1 ha. The model created grids of 20 x 12 cells. For the residential and townhome development, runoff from the roadways is directed onto the grass. Surface runoff of each cell is calculated differently which contained bio retention facility and with cisterns. Cisterns are used only to intercept the rooftop runoff. Outflow from the cistern is drained through the orifice. Once the storage of the cistern is reached, the outflow occurs through the cistern. In the bio retention cells once the depth of the stored water exceeds the storage it overflow where the overflow is equal to total volume of water in storage minus the maximum storage capacity of the facility and this is directed to the down gradient cell.
Results:
Onsite effects on the development
The comparison was made between the type of land pattern (forest, residential, townhome, and commercial) with respect to the two hydrologic metrics i.e. peak discharge and the total volume. It was observed that 1 yr storm was totally infiltrated in the forest pattern i.e. pre development condition. The development patterns have reduced the infiltration potential by increasing the impervious cover.
Effectiveness of cisterns
Effectiveness of cisterns was studied by analyzing the different land patterns with 1 and 2 yr storm events. It was observed that cisterns were more effective with smaller storm, there was about 30% reduction of peak discharge for single family lot for 1 yr storm where as it was only 10% reduction for 2 yr rainfall. If cistern is the only type of BMP in the site then they are ineffective for 2 yr storm, where as they provide some control for smaller events. Volume of cistern should be based on the volume of the runoff at the time of maximum rainfall intensity.
Effectiveness of bio retention location
For the study they have considered the location of bio retention near the cistern overflow, around the outlet of the micro watershed, along the roadway in residential/townhome lot and along the parking lot in commercial lot. There was effective reduction in the runoff volume when bio retention intercepted the roadway runoff and cisterns intercepted the rooftop runoff. But considering the bio retention at the overflow of the cisterns was more effective in reducing the peak discharge, as cisterns storage is reached before the highest storm intensity with bio retention facility there would be storage to control the peak. Location and volume of BMP is dependent on the time of distribution of the rainfall event. Location of bioretention did not make much of a reduction in the total runoff volume as the impervious land cover was greater when compared to the bio retention storage. Whereas peak discharge was decreased with the cisterns storing the runoff and overflow from the cisterns was drained to bio retention facilities.
Effect of storage volume
It was observed that effect of storage volume depends majorly on the land use type. For 1 yr storm event for commercial lot, it was noticed that when the facilities were doubled the peak discharge was reduced by 10% and volume to 30%. Author makes an observation that number of additional facilities is dependent on each watershed which might improve the hydrology.
Varying effects on hydrologic metrics
The two metrics considered to measure the effectiveness of the LID are peak discharge and total runoff volume. Effect of changing the volume of the storage on these two metrics vary as runoff volume can be controlled with the increased storage
Discussion:
I personally found this article interesting as they have tried to check the effectiveness of the LID’s considered, which would be similar to what I am trying to do in my thesis. Check the effectiveness of the RHS and PP in improving the hydrologic condition of the study area. This paper would be helpful when I take up the option of optimizing the location of the LID’s I am considering. For my thesis I would like to measure the two metrics they have mentioned and use Marcio’s HFR metric to analyze the impacts.
Monday, June 29, 2009
Discussion # 3 (26 June 2009)
Article Reference:
David J Sample, James P Heaney, Integrated Management of Irrigation and Urban Storm Water Infiltration, October 2006, Journal of Water Resource Planning and Management
Introduction:
The paper focuses on integrating the water conservation, irrigation management planning and storm management for a study area of a subdivision in Boulder, Colorado. Paper illustrates different studies carried out in integrating the storm water and usage of LID techniques which has received recent attention in the research community. According to the studies carried out LID is considered to be better mimic of the pre development conditions and LID relies in managing the runoff at the site thereby reducing the directly connected impervious area (DCIA) thereby reducing the storm runoff produced. DCIA runoff as is collected by the storm conveyance system which have the potential of being transported away from the irrigation users, therefore for in-site storm management we need concentrate on the non-DCIA and pervious areas.
Methodology:
Study area: Sub-division of Boulder, CO
Area: 11 acres
Drainage: generally running downward to the swale to the south
Approach used in hydrologic analysis: simple water budget principles (setting a control volume around the soil column)
Method to determine Infiltration: Green Ampt Method (Parameters dependent are hydraulic conductivity, soil suction head and difference between the moisture content and porosity)
Network: Building runoff (impervious) is directed to the pervious areas and eventually drained into the conveyance channel.
First approach:
• They used the weather data to predict the PET (hourly)
• Infiltration, Runoff is calculated using Green Ampt method (5 min)
• Soil Moisture conditions assumed to be same over the hour
• Irrigation/rainfall (hourly)
• Total Water balance is estimated using (Infiltration, runoff, rainfall, soil moisture, and irrigation)
• Runoff from each impervious block is determined by routing through the drainage channel
Comparative approach:
• SCS method to estimate the rainfall-runoff response
• Model depends on CN and time of concentration
• Varying the CN with hydrologic conditions will adapt the model to different soil moisture conditions
Cost Estimating Procedure:
In order to evaluate different water management options we need to see the cost effectiveness of different approaches on micro level. From customers point of view the cost can be split into three categories- Water use, on site water management and water pollution control. Investments made on on-site water management typically reduce the water use costs. Water pollution control cost is mostly not borne by the customer unless there is substantial outdoor water demand.
Results:
They have carried out different options of irrigation management plans and studied the water budget of the area. Few of the options studied are mentioned below:
• No irrigation
• Irrigation 1in/week
• Irrigation 2in/week
• Irrigation = 70% of 24 h ET
• Irrigation = 1 in/week with soil moisture sensor which cuts off the irrigation once the soil is saturated
• Irrigation = 1 in/week with Rain water storage (50000L) which is 50% full therefore 50% is catered to peak flow control
Cost comparison was carried out between these options with respect to the three categories of the outdoor costs. They have carried out study to find out the optimal rain water storage volume to result in highest net benefits, it was found to be for the capacity of 10000L that results in highest net benefit.
Discussion:
Author concludes about how the most benefited (Net benefit) option is associated with conserving the water (storing in cisterns) for the irrigation options. I was not very sure about how they have calculated the cost components for the irrigation options they have considered. On a whole this paper was very informative about how the design and analysis of the combining water supply and storm water management is done. This paper will be very useful for my literature review and would be helpful if I further extend my research taking into consideration the irrigation plans for the rain water harvesting.
David J Sample, James P Heaney, Integrated Management of Irrigation and Urban Storm Water Infiltration, October 2006, Journal of Water Resource Planning and Management
Introduction:
The paper focuses on integrating the water conservation, irrigation management planning and storm management for a study area of a subdivision in Boulder, Colorado. Paper illustrates different studies carried out in integrating the storm water and usage of LID techniques which has received recent attention in the research community. According to the studies carried out LID is considered to be better mimic of the pre development conditions and LID relies in managing the runoff at the site thereby reducing the directly connected impervious area (DCIA) thereby reducing the storm runoff produced. DCIA runoff as is collected by the storm conveyance system which have the potential of being transported away from the irrigation users, therefore for in-site storm management we need concentrate on the non-DCIA and pervious areas.
Methodology:
Study area: Sub-division of Boulder, CO
Area: 11 acres
Drainage: generally running downward to the swale to the south
Approach used in hydrologic analysis: simple water budget principles (setting a control volume around the soil column)
Method to determine Infiltration: Green Ampt Method (Parameters dependent are hydraulic conductivity, soil suction head and difference between the moisture content and porosity)
Network: Building runoff (impervious) is directed to the pervious areas and eventually drained into the conveyance channel.
First approach:
• They used the weather data to predict the PET (hourly)
• Infiltration, Runoff is calculated using Green Ampt method (5 min)
• Soil Moisture conditions assumed to be same over the hour
• Irrigation/rainfall (hourly)
• Total Water balance is estimated using (Infiltration, runoff, rainfall, soil moisture, and irrigation)
• Runoff from each impervious block is determined by routing through the drainage channel
Comparative approach:
• SCS method to estimate the rainfall-runoff response
• Model depends on CN and time of concentration
• Varying the CN with hydrologic conditions will adapt the model to different soil moisture conditions
Cost Estimating Procedure:
In order to evaluate different water management options we need to see the cost effectiveness of different approaches on micro level. From customers point of view the cost can be split into three categories- Water use, on site water management and water pollution control. Investments made on on-site water management typically reduce the water use costs. Water pollution control cost is mostly not borne by the customer unless there is substantial outdoor water demand.
Results:
They have carried out different options of irrigation management plans and studied the water budget of the area. Few of the options studied are mentioned below:
• No irrigation
• Irrigation 1in/week
• Irrigation 2in/week
• Irrigation = 70% of 24 h ET
• Irrigation = 1 in/week with soil moisture sensor which cuts off the irrigation once the soil is saturated
• Irrigation = 1 in/week with Rain water storage (50000L) which is 50% full therefore 50% is catered to peak flow control
Cost comparison was carried out between these options with respect to the three categories of the outdoor costs. They have carried out study to find out the optimal rain water storage volume to result in highest net benefits, it was found to be for the capacity of 10000L that results in highest net benefit.
Discussion:
Author concludes about how the most benefited (Net benefit) option is associated with conserving the water (storing in cisterns) for the irrigation options. I was not very sure about how they have calculated the cost components for the irrigation options they have considered. On a whole this paper was very informative about how the design and analysis of the combining water supply and storm water management is done. This paper will be very useful for my literature review and would be helpful if I further extend my research taking into consideration the irrigation plans for the rain water harvesting.
Friday, June 12, 2009
Discussion # 1 (12 June 2009)
Article Reference:
Evan Shane Williams and William R. Wise, Hydrologic Impacts of Alternative Approaches to Storm Water Management and Land Development, April 2006, Journal of the American Water Resource Association
Introduction:
The paper discusses of the hydrologic impacts caused by different alternatives of storm management and land development options. The study is carried out based on four alternatives-
1. Traditional land development (full lot size as specified by county rules) with conventional (i.e. pond) storm management system
2. Cluster development i.e. reducing the lot size to half with conventional (i.e. pond) storm management system
3. Traditional land development with LID technique i.e. emphasizing on vertical storage
4. Cluster land development with LID technique i.e. emphasizing on vertical storage
Along with these alternatives they studied how the hydrology is affected with connected (runoff from impervious cover being discharged into the conveyance system directly without any infiltration i.e. implying no vertical storage) and disconnected impervious cover (allowing infiltration i.e. rooftop runoff discharged into lawns and roads draining to swales).
Above mentioned different alternatives were compared with the existing conditions i.e. without the land development.
Results:
Peak flow: Scenarios studied- Existing, without depression storage and with depressions storage. It was observed that two year peak timing change was minimal when compared to 25 yr storm event. LID designs could not meet the peak flow control without the depression storage.
Runoff Volume: Reduction in the runoff volume was observed when the footprint was reduced and using the directly connecting systems. Further reduction of volume was noticed with the usage of infiltration.
The results show that when they ran a continuous model (4 months data) which showed that LID did not perform as expected especially during tropical storms as the soil moisture content is greater than the average condition.
Conclusion:
Infiltration based storm management might perform worse when the soil moisture are above the average value thereby reducing the infiltration or percolation rate. Author mentions about using LID to control the peak upto a certain event beyond which depression storage need to used to control the larger events with this both the quality and quantity concerns are met. This study basically illustrates the impact of using connect and disconnected impervious cover, different types of developments (traditional and clustered type) and usage of conventional pond in addition to infiltration media.
Discussion:
There have been many limitations associated with the study such as using lumped modeling approach, but then this study gives a idea of how the different land developments and different storm management techniques could affect the hydrology of the watershed. This study illustrates how conventional pond system would be required even along with LID (infiltration based) to meet the peak flow control requirement for larger storms.
This paper though doesnot speak about different types of LID’s which could be used, it explains about how the hydrology is differed with different planning methods. In the similar grounds I would like to compare the behavior of the catchment hydrology based on the LID strategies I am going to consider. Through this paper I got the idea of what are all the components of comparison I can make between the scenarios or alternatives I run.
Evan Shane Williams and William R. Wise, Hydrologic Impacts of Alternative Approaches to Storm Water Management and Land Development, April 2006, Journal of the American Water Resource Association
Introduction:
The paper discusses of the hydrologic impacts caused by different alternatives of storm management and land development options. The study is carried out based on four alternatives-
1. Traditional land development (full lot size as specified by county rules) with conventional (i.e. pond) storm management system
2. Cluster development i.e. reducing the lot size to half with conventional (i.e. pond) storm management system
3. Traditional land development with LID technique i.e. emphasizing on vertical storage
4. Cluster land development with LID technique i.e. emphasizing on vertical storage
Along with these alternatives they studied how the hydrology is affected with connected (runoff from impervious cover being discharged into the conveyance system directly without any infiltration i.e. implying no vertical storage) and disconnected impervious cover (allowing infiltration i.e. rooftop runoff discharged into lawns and roads draining to swales).
Above mentioned different alternatives were compared with the existing conditions i.e. without the land development.
Results:
Peak flow: Scenarios studied- Existing, without depression storage and with depressions storage. It was observed that two year peak timing change was minimal when compared to 25 yr storm event. LID designs could not meet the peak flow control without the depression storage.
Runoff Volume: Reduction in the runoff volume was observed when the footprint was reduced and using the directly connecting systems. Further reduction of volume was noticed with the usage of infiltration.
The results show that when they ran a continuous model (4 months data) which showed that LID did not perform as expected especially during tropical storms as the soil moisture content is greater than the average condition.
Conclusion:
Infiltration based storm management might perform worse when the soil moisture are above the average value thereby reducing the infiltration or percolation rate. Author mentions about using LID to control the peak upto a certain event beyond which depression storage need to used to control the larger events with this both the quality and quantity concerns are met. This study basically illustrates the impact of using connect and disconnected impervious cover, different types of developments (traditional and clustered type) and usage of conventional pond in addition to infiltration media.
Discussion:
There have been many limitations associated with the study such as using lumped modeling approach, but then this study gives a idea of how the different land developments and different storm management techniques could affect the hydrology of the watershed. This study illustrates how conventional pond system would be required even along with LID (infiltration based) to meet the peak flow control requirement for larger storms.
This paper though doesnot speak about different types of LID’s which could be used, it explains about how the hydrology is differed with different planning methods. In the similar grounds I would like to compare the behavior of the catchment hydrology based on the LID strategies I am going to consider. Through this paper I got the idea of what are all the components of comparison I can make between the scenarios or alternatives I run.
Sunday, April 26, 2009
Assignment # 10 (2)
Article Reference:
Tze Chin Pan, Jehng Jung Kao, GA-QP Model to Optimize Sewer System Design, January 2009, Journal of Environmental Engineering
Summary:
The paper explains the importance of optimizing the sewer network (Pipe diameter, pipe slopes, pipe buried depths etc) in reducing the total cost of establishing the sewer system. Optimizing sewer network is difficult because of few typical constraints associated in the design. Typical constraints are – maintaining minimum velocity (for self cleansing), preventing maximum velocity (which causes scouring), upstream elevation greater than the downstream elevation giving sufficient slope for the flow, designing the depth to accommodate the flow of the design capacity, commercially available pipe diameters, and ensuring the diameter of the downstream pipes to be greater or equal than the upstream pipes thereby letting the downstream pipes to carry cumulative flow. Many approaches have been developed to design sewer network. One such approach was using discrete differential dynamic programming (DDDP), but this approach restricts the search space which reduces the opportunities locate global optimum. Pan and Kao used combined GA and QP as QP is a better way of representing a non linear cost function than LP where you need to convert the nonlinear functions to linear by piecewise linearization. As few of the design factors such as geology, traffic impact, people’s preference, land availability etc are not considered in the study as they are difficult to model. Authors mention that the solution obtained from this model would not be feasible when un-modeled factors are evaluated. This paper explains modeling a different Modeling for Generating Alternative (MGA) function to evaluate the difference between the results obtained from GA-QP and DDDP models.
GA Model components-
Genes: Pipe and pumping station locations in binary code
Chromosomes: Pipe diameters and pumping locations which represent a design layout of the sewer system.
Fitness function: Reciprocal of the cost function (1/Cost of chromosome)
Selection Process: Based on greater the area on the wheel higher the probability being chosen (Simpson et.al. 1994)
Crossover: Random mother chromosomes binary (gene) information is exchanged to generate two child chromosomes.
Mutation: Changes the binary information randomly
The values of the genes are randomly produced. All the unacceptable chromosomes are discarded than repairing as it is too complex, thus producing new set of chromosomes. The two major constraints in deciding the acceptability of the chromosomes are – pipe having required flow capacity (i.e dia of pipe should be capable to carry the flow) and maintain flow continuity (i.e d/s dia is greater than the u/s). Fitness function used in the GA model to evaluate the fitness of the chromosomes generated is defined as the reciprocal of the cost function. Therefore chromosomes with high fitness value are superior to the chromosome with low fitness value. Selection, mutation and crossover are used to create new set of chromosomes. As the cost decreases, the fitness value increases thereby occupying greater area on the wheel which increases the probability of being selected for crossover. The Crossover process exchanges pipe diameters and pumping locations of randomly generated chromosomes to generated new set of chromosomes. Mutation randomly changes the binary information in the chromosomes so that they are not stuck with the local optimum.
Quadratic Programming-
This study has used QP to evaluate the fitness value of the chromosome. The objective function includes – construction cost of pipe based on the diameter, depth and the length, construction cost of manhole and construction cost of pumping station. The authors have constrained the flow velocities and depth by limiting the pipe slope. All the sewer pipes need to be buried at a specific depth from the ground so as to be able to connect the household waste flow. Therefore the decision variables associated in this model are pipe slopes and the buried depths of the downstream end of the pipes.
MGA identifies maximally different solutions which could still be regarded as good and different alternatives.
Discussion:
The authors have explained in detail how each component of GA is taken into consideration. Implementation of GA in the real time practical models is clearer to me after reading this paper. It is true as mentioned by Author about the solution not being feasible without taking into account few factors like land availability, geology etc, which is considered to be of major component in the designing procedure. This paper carries out a practical case explanation of importance of having generating alternative solutions as discussed in the earlier article by Brill.The comparison of different results/solutions DDDP, GA, MGA1, and MGA2 clearly explains the importance of having a feasible alternative which could be considered when all the non considered factors are evaluated into these solutions. Every individual sewer system has specific concern which could not be modeled mathematically into the model, this approach of generating alternatives would be helpful to see and evaluate the feasibility of these factors along with the optimization solution obtained from the GA model. This would be more of a practical approach than just optimizing without considering these factors which are vital in the decisions of these systems.
Tze Chin Pan, Jehng Jung Kao, GA-QP Model to Optimize Sewer System Design, January 2009, Journal of Environmental Engineering
Summary:
The paper explains the importance of optimizing the sewer network (Pipe diameter, pipe slopes, pipe buried depths etc) in reducing the total cost of establishing the sewer system. Optimizing sewer network is difficult because of few typical constraints associated in the design. Typical constraints are – maintaining minimum velocity (for self cleansing), preventing maximum velocity (which causes scouring), upstream elevation greater than the downstream elevation giving sufficient slope for the flow, designing the depth to accommodate the flow of the design capacity, commercially available pipe diameters, and ensuring the diameter of the downstream pipes to be greater or equal than the upstream pipes thereby letting the downstream pipes to carry cumulative flow. Many approaches have been developed to design sewer network. One such approach was using discrete differential dynamic programming (DDDP), but this approach restricts the search space which reduces the opportunities locate global optimum. Pan and Kao used combined GA and QP as QP is a better way of representing a non linear cost function than LP where you need to convert the nonlinear functions to linear by piecewise linearization. As few of the design factors such as geology, traffic impact, people’s preference, land availability etc are not considered in the study as they are difficult to model. Authors mention that the solution obtained from this model would not be feasible when un-modeled factors are evaluated. This paper explains modeling a different Modeling for Generating Alternative (MGA) function to evaluate the difference between the results obtained from GA-QP and DDDP models.
GA Model components-
Genes: Pipe and pumping station locations in binary code
Chromosomes: Pipe diameters and pumping locations which represent a design layout of the sewer system.
Fitness function: Reciprocal of the cost function (1/Cost of chromosome)
Selection Process: Based on greater the area on the wheel higher the probability being chosen (Simpson et.al. 1994)
Crossover: Random mother chromosomes binary (gene) information is exchanged to generate two child chromosomes.
Mutation: Changes the binary information randomly
The values of the genes are randomly produced. All the unacceptable chromosomes are discarded than repairing as it is too complex, thus producing new set of chromosomes. The two major constraints in deciding the acceptability of the chromosomes are – pipe having required flow capacity (i.e dia of pipe should be capable to carry the flow) and maintain flow continuity (i.e d/s dia is greater than the u/s). Fitness function used in the GA model to evaluate the fitness of the chromosomes generated is defined as the reciprocal of the cost function. Therefore chromosomes with high fitness value are superior to the chromosome with low fitness value. Selection, mutation and crossover are used to create new set of chromosomes. As the cost decreases, the fitness value increases thereby occupying greater area on the wheel which increases the probability of being selected for crossover. The Crossover process exchanges pipe diameters and pumping locations of randomly generated chromosomes to generated new set of chromosomes. Mutation randomly changes the binary information in the chromosomes so that they are not stuck with the local optimum.
Quadratic Programming-
This study has used QP to evaluate the fitness value of the chromosome. The objective function includes – construction cost of pipe based on the diameter, depth and the length, construction cost of manhole and construction cost of pumping station. The authors have constrained the flow velocities and depth by limiting the pipe slope. All the sewer pipes need to be buried at a specific depth from the ground so as to be able to connect the household waste flow. Therefore the decision variables associated in this model are pipe slopes and the buried depths of the downstream end of the pipes.
MGA identifies maximally different solutions which could still be regarded as good and different alternatives.
Discussion:
The authors have explained in detail how each component of GA is taken into consideration. Implementation of GA in the real time practical models is clearer to me after reading this paper. It is true as mentioned by Author about the solution not being feasible without taking into account few factors like land availability, geology etc, which is considered to be of major component in the designing procedure. This paper carries out a practical case explanation of importance of having generating alternative solutions as discussed in the earlier article by Brill.The comparison of different results/solutions DDDP, GA, MGA1, and MGA2 clearly explains the importance of having a feasible alternative which could be considered when all the non considered factors are evaluated into these solutions. Every individual sewer system has specific concern which could not be modeled mathematically into the model, this approach of generating alternatives would be helpful to see and evaluate the feasibility of these factors along with the optimization solution obtained from the GA model. This would be more of a practical approach than just optimizing without considering these factors which are vital in the decisions of these systems.
Assignment # 10 (1)
Article Reference:
E. Downey Brill, The Use of Optimization Models in Public Sector Planning, May 1979, Management Science
Summary:
The paper discusses about how solutions obtained from optimization model for the public sector problems are not very useful as there is a multitude of local optima and as these models do not formulate essential planning elements. Because of this omitted planning elements the solutions may actually lie in the inferior region than along the non-inferior frontier. Many of the early public sector optimization models concentrated majorly on the economic efficiency objective. Two of the difficulties in these models were that they failed considering equity and empirical shortcomings in estimation of benefits and costs. The author’s mention that even by using multi objective model which is used to capture all the issues pertaining to the problem, it would be impractical to generate complete set of trade off relationships.
Author quotes the recommendation made by Liebman that these optimization models should not be used to resolve the wicked problems instead they should be used to provide understanding and insight of the problem which supplements the decision makers. As explained by Liebman if we consider these components in out planning process than our models needs to be formulated differently and using different computer codes to met the requirements. The paper explains the methods of using the optimization model in combination with other models to include the elements of conventional planning and generating alternative solutions which could be used in the planning process. Authors explain about how the optimization could be used to generate alternative solutions and assisting in evaluating the solutions. To enhance these optimization models to aid creative planning process, the generated solutions should meet the minimum required and the solutions should be different. With the help of these alternative solutions the planners are able to gain better understanding of the objective, constraints and relationships of the problem. These generations of alternative solutions acts as catalyst for human creativity and inventions in making new solutions.
Discussion:
This paper is an extension of Liebman’s article who explained about many public sector problems to be wicked problems and these problems could be tackled by understanding, insight and intuitive of the problem. The solutions obtained by the optimization model are usually not very helpful as these do not consider the vital factors which are involved in the planning process, thereby making those solutions infeasible. This paper extends this discussion based on the usage of optimization models and how these models could incorporate all the omitted components of the planning process to land up at practically feasible solutions. I feel the approach of generating alternative solutions is more a practical approach as many models decisions are majorly dependent on the factors which might not be formulated mathematically. With these alternative solutions it would be an aid for the planner to come up with better practical solutions.
E. Downey Brill, The Use of Optimization Models in Public Sector Planning, May 1979, Management Science
Summary:
The paper discusses about how solutions obtained from optimization model for the public sector problems are not very useful as there is a multitude of local optima and as these models do not formulate essential planning elements. Because of this omitted planning elements the solutions may actually lie in the inferior region than along the non-inferior frontier. Many of the early public sector optimization models concentrated majorly on the economic efficiency objective. Two of the difficulties in these models were that they failed considering equity and empirical shortcomings in estimation of benefits and costs. The author’s mention that even by using multi objective model which is used to capture all the issues pertaining to the problem, it would be impractical to generate complete set of trade off relationships.
Author quotes the recommendation made by Liebman that these optimization models should not be used to resolve the wicked problems instead they should be used to provide understanding and insight of the problem which supplements the decision makers. As explained by Liebman if we consider these components in out planning process than our models needs to be formulated differently and using different computer codes to met the requirements. The paper explains the methods of using the optimization model in combination with other models to include the elements of conventional planning and generating alternative solutions which could be used in the planning process. Authors explain about how the optimization could be used to generate alternative solutions and assisting in evaluating the solutions. To enhance these optimization models to aid creative planning process, the generated solutions should meet the minimum required and the solutions should be different. With the help of these alternative solutions the planners are able to gain better understanding of the objective, constraints and relationships of the problem. These generations of alternative solutions acts as catalyst for human creativity and inventions in making new solutions.
Discussion:
This paper is an extension of Liebman’s article who explained about many public sector problems to be wicked problems and these problems could be tackled by understanding, insight and intuitive of the problem. The solutions obtained by the optimization model are usually not very helpful as these do not consider the vital factors which are involved in the planning process, thereby making those solutions infeasible. This paper extends this discussion based on the usage of optimization models and how these models could incorporate all the omitted components of the planning process to land up at practically feasible solutions. I feel the approach of generating alternative solutions is more a practical approach as many models decisions are majorly dependent on the factors which might not be formulated mathematically. With these alternative solutions it would be an aid for the planner to come up with better practical solutions.
Monday, April 13, 2009
Reading Assignment # 9
Article Reference:
Jenq-Tzong Shiau, Fu Chun Wu, Compromise Programming Methodology for Determining Instream Flow Under Multi-Objective Water Allocation Criteria, 2006, Journal of American Water Resource Association
Summary:
The paper by Jenq Tzong and Fu chun determines a quantitative assessment for determining in-stream flow under multi objective water allocation criteria. They explain the concept of compromise programming which is used to optimize water allocation scheme by minimizing hydrologic alterations and water supply shortages. This methodology was applied to a case study of Kaoping diversion weir in Taiwan. The paper focuses on evaluating the hydrologic alterations of the weir and the optimal operation schemes.
The Kaoping diversion weir was constructed to meet the increasing municipal water demands. The design diversion capacity for the municipal use is about 35 cumec. However prior to the construction there was long history of agricultural water withdrawals from the downstream of the Kaoping creek. From the data it is observed that there has been no flow diversion during dry season for meeting municipal demand due to insufficient amount of water. The operation model of weir has three components – meeting the reserved agricultural water demand, providing projected municipal water demand and instream flow release. Based on the environmental protection, they have set different priorities, first being instream flow release, second priority being registered agricultural demand and third priority being projection flow for municipal demand.
Range of variability of approach has been used to evaluate the hydrologic alterations caused by the flow diversions of the weir. RVA assesses the hydrologic regime with respect to 32 ecological relevant indicators of hydrologic alteration (IHA). As suggested by Richter et al. (1998) RVA range of variation for each IHA is taken as 25th and 75th percentile pre diversion values. Weir operations are aimed such that pre diversion flow conditions reach the targeted RVA ranges. Overall degree of hydrologic alteration (D) is estimated to measure the deviation between post impact flow regime and pre impact flow regime. Richter et al. (1998) classified the overall degree of alterations as low, medium and high alteration. Therefore value of D for a particular IHA quantifies the effect of flow diversion on the flow regime. For including these overall hydrologic alteration index needs to be estimated. Richter et al. suggested the method of averaging the 32 IHA degrees so as to have an overall impact index. By using this averaged index, high impact alterations would be offset by the low degree alterations. This paper considers the method proposed by Shiau and Wu (2004b) which calculates the single index for hydrologic alteration in categories of high and medium alterations.
A water supply deficit is estimated when the actual demand is greater than the registered or projected demand. In the optimizing model, water supply objective is to minimize the shortage ratio (total deficit / total demand) of agricultural water and municipal demand. Minimizing both hydrologic alterations and supply shortages is the goal of Kaoping diversion weir which is formulated as a multi objective programming.
Min {SRW, SRD, D}
SRW = supply shortage of registered agricultural withdrawals
SRD = supply shortage of projected municipal uses
D = overall degree of hydrologic alteration
All these supply shortages values are the function of the instream flow value (i.e. decision variable). There are many techniques used to deal with the multi objective problems, this study considers using of compromising programming.
Compromising programming estimates the optimal solution which has the least distance from the ideal point (i.e. point where multiple objectives reach the optimal solution). This compromise programming is carried out in two steps –
1. First the best and worst solutions of both the objective functions needs to be found which is within the computation domain (which is found out based on the decision variable- instream flow)
2. Seeking the optimal solution by calculating the shortest distance to the best estimated point
In the current operation of the weir, it releases a minimum of 9.5 cumec instream flow. The overall hydrologic alteration is about 69.3% i.e categorized as highly altered. Though agricultural withdrawals are the highest priority 18% shortage of water exists when compared to 6% of municipal water shortage. With the highest percentage of alteration it is evident that the present instream release is not sufficient to restore the natural flow variability. To evaluate effect of different instream flows, Shiau and Wu studied different flows ranging from o to 100 cumec. Corresponding SRW, SRD, D and value of L were estimated. This study showed that SRW increased rapidly with smaller instream than that of larger instream flow. SRD increased linearly. Value of D decreased with the increase in the instream flow. Two drops were observed – one (26 cumec) to convert from highly altered to medium alteration and the second drop (93 cumec) to convert from medium alteration to low alteration. For a given instream flow the SRW, SRD and D values are fixed, but the value of L changes with respect to the weighing factors. Therefore a study of various weighting factors was considered to see how the instream flow and the Minimum distance L is changed. The proposed optimal instream flow 26 cumec would not be able to restore the altered hydrologic regime to pre diversion condition but then it helps in mitigating the adverse effects of the highly and moderately altered IHA’s.
Discussion:
The paper was very informative about how we can optimize a model considering multi objectives i.e. minimizing water shortages and hydrologic alterations. With the increase of municipal demands, many reservoirs have been affecting the riverine environment by reduced instream flow. By using the quantitative assessment of 32 relevant IHA’s it would be helpful to check the hydrologic alterations caused due to this reduced instream flow. Future research would obviously be considering the biological component into the RVA. It would be interesting to note the changes in the optimized results with the added biological component. Compromising programming is a useful technique which can be used in many models to optimize two conflicting objectives for example flood management vs. downstream eco system,
Jenq-Tzong Shiau, Fu Chun Wu, Compromise Programming Methodology for Determining Instream Flow Under Multi-Objective Water Allocation Criteria, 2006, Journal of American Water Resource Association
Summary:
The paper by Jenq Tzong and Fu chun determines a quantitative assessment for determining in-stream flow under multi objective water allocation criteria. They explain the concept of compromise programming which is used to optimize water allocation scheme by minimizing hydrologic alterations and water supply shortages. This methodology was applied to a case study of Kaoping diversion weir in Taiwan. The paper focuses on evaluating the hydrologic alterations of the weir and the optimal operation schemes.
The Kaoping diversion weir was constructed to meet the increasing municipal water demands. The design diversion capacity for the municipal use is about 35 cumec. However prior to the construction there was long history of agricultural water withdrawals from the downstream of the Kaoping creek. From the data it is observed that there has been no flow diversion during dry season for meeting municipal demand due to insufficient amount of water. The operation model of weir has three components – meeting the reserved agricultural water demand, providing projected municipal water demand and instream flow release. Based on the environmental protection, they have set different priorities, first being instream flow release, second priority being registered agricultural demand and third priority being projection flow for municipal demand.
Range of variability of approach has been used to evaluate the hydrologic alterations caused by the flow diversions of the weir. RVA assesses the hydrologic regime with respect to 32 ecological relevant indicators of hydrologic alteration (IHA). As suggested by Richter et al. (1998) RVA range of variation for each IHA is taken as 25th and 75th percentile pre diversion values. Weir operations are aimed such that pre diversion flow conditions reach the targeted RVA ranges. Overall degree of hydrologic alteration (D) is estimated to measure the deviation between post impact flow regime and pre impact flow regime. Richter et al. (1998) classified the overall degree of alterations as low, medium and high alteration. Therefore value of D for a particular IHA quantifies the effect of flow diversion on the flow regime. For including these overall hydrologic alteration index needs to be estimated. Richter et al. suggested the method of averaging the 32 IHA degrees so as to have an overall impact index. By using this averaged index, high impact alterations would be offset by the low degree alterations. This paper considers the method proposed by Shiau and Wu (2004b) which calculates the single index for hydrologic alteration in categories of high and medium alterations.
A water supply deficit is estimated when the actual demand is greater than the registered or projected demand. In the optimizing model, water supply objective is to minimize the shortage ratio (total deficit / total demand) of agricultural water and municipal demand. Minimizing both hydrologic alterations and supply shortages is the goal of Kaoping diversion weir which is formulated as a multi objective programming.
Min {SRW, SRD, D}
SRW = supply shortage of registered agricultural withdrawals
SRD = supply shortage of projected municipal uses
D = overall degree of hydrologic alteration
All these supply shortages values are the function of the instream flow value (i.e. decision variable). There are many techniques used to deal with the multi objective problems, this study considers using of compromising programming.
Compromising programming estimates the optimal solution which has the least distance from the ideal point (i.e. point where multiple objectives reach the optimal solution). This compromise programming is carried out in two steps –
1. First the best and worst solutions of both the objective functions needs to be found which is within the computation domain (which is found out based on the decision variable- instream flow)
2. Seeking the optimal solution by calculating the shortest distance to the best estimated point
In the current operation of the weir, it releases a minimum of 9.5 cumec instream flow. The overall hydrologic alteration is about 69.3% i.e categorized as highly altered. Though agricultural withdrawals are the highest priority 18% shortage of water exists when compared to 6% of municipal water shortage. With the highest percentage of alteration it is evident that the present instream release is not sufficient to restore the natural flow variability. To evaluate effect of different instream flows, Shiau and Wu studied different flows ranging from o to 100 cumec. Corresponding SRW, SRD, D and value of L were estimated. This study showed that SRW increased rapidly with smaller instream than that of larger instream flow. SRD increased linearly. Value of D decreased with the increase in the instream flow. Two drops were observed – one (26 cumec) to convert from highly altered to medium alteration and the second drop (93 cumec) to convert from medium alteration to low alteration. For a given instream flow the SRW, SRD and D values are fixed, but the value of L changes with respect to the weighing factors. Therefore a study of various weighting factors was considered to see how the instream flow and the Minimum distance L is changed. The proposed optimal instream flow 26 cumec would not be able to restore the altered hydrologic regime to pre diversion condition but then it helps in mitigating the adverse effects of the highly and moderately altered IHA’s.
Discussion:
The paper was very informative about how we can optimize a model considering multi objectives i.e. minimizing water shortages and hydrologic alterations. With the increase of municipal demands, many reservoirs have been affecting the riverine environment by reduced instream flow. By using the quantitative assessment of 32 relevant IHA’s it would be helpful to check the hydrologic alterations caused due to this reduced instream flow. Future research would obviously be considering the biological component into the RVA. It would be interesting to note the changes in the optimized results with the added biological component. Compromising programming is a useful technique which can be used in many models to optimize two conflicting objectives for example flood management vs. downstream eco system,
Monday, March 30, 2009
Assignment # 8
Article Reference:
T.R Neelakantan, N.V. Pundarikanthan, Neural Network-Based Simulation-Optimization Model for Reservoir Operation, Mar-Apr 2008, Journal of Water Resources Planning and Management
Summary:
The paper focuses on planning a model for reservoir operation which uses simulation-optimization approach. Author takes Chennai water supply as the study area. Reservoir planning was improved by demand management using the hedging rule which distributes the deficits for longer time by rationing water supply. For defining and optimizing the decision variables for hedging rule, the neural network based simulation model was used as a sub model to the Hookes and Jeeves programming model. Simulation analysis requires a operation policy, a standard policy is the optimal policy where the objective is to minimize the total deficit over the time. Hedging and rationing rule helps in distributing the deficit over a longer time. The total storage in the reservoir is divided into different zones and based on the falling level in each zone the release target can be fixed. For the study the reservoir is divided into four zones and the storage levels are S1, S2 and S3. This simulation model is sent as sub model to the Hookes and jeeves nonlinear programming model which passed management decision vectors to the simulation model to find the objective function as an output.
The whole study has been carried out in various stages. In the first stage the back propagation neural network is used to simulate the reservoir operation. Further in the second stage this neural network was fed as sub model to Hookes and Jeeves, this combined simulation-optimization model is used to screen the operation policies. In the third stage the best solution of the optimization is fine tuned using the conventional simulation-optimization model.
Authors have considered Chennai water supply as the study area. Chennai’s water supply is catered through three reservoirs- Poondi, Cholavaram and Red hills and ground water sources. The reservoirs are fed only by the north east monsoon which lasts only for three months. Due to increased extraction of ground water, the water table fell rapidly and there are traces of sea water intrusion. They have planned for the augmentation of the system by Krishna water. With the new excess water they have proposed to use Chembarambakkam reservoir as one of the terminal reservoirs. As Chennai is facing severe drought conditions the criteria would be to reduce the shortfalls as much as possible. During the drought condition the water supply managers prefer smaller shortfalls than dealing with larger ones and therefore they are following the method of hedging and rationing. Distribution of deficits should be done in such a way that they are spread for a longer period and with lesser magnitude. To do the above deficit index (sum of squared deficits) is followed which should be minimum among the other options. With the augmentation of Krishna water supply, equity of reservoir levels for two parallel reservoirs (Red Hills and Chembarambakkam) needs to be maintained. So the demand ratio needs to be 1:x and the deficit ratio to 1:x. As deficit index is the second order parameter the ratio between the two reservoirs needs to be 1:x^2.
The simulation model uses the mass balance principle and follows the constraints on canal capacity, minimum and maximum storage capacity, and evaporation loss and so on. The objective function is to minimize the deficit index by changing the decision management variables S1, S2, and S3 (Storage levels). The study was carried out using different scenarios considering different source and terminal reservoirs, to estimate which combination proves to improve the objective function. Inflow data into the reservoirs are studied to see the performance of the reservoir. Authors have considered catchment inflow, percolation loss, and transmission losses to be negligible. The study was carried out with different supply levels – full demand, 80% demand 75% demand, 67% demand and 50% demand.
Discussion:
This paper was interesting as the study deals with how we can optimize the operating policy based on the hedging rule. As this model is flexible to include various reservoirs and more complex system, I think it is a good model to carry out such a study. It has the flexibility of changing the nonlinear programming model instead of Hookes and Jeeves, which would be interesting to explore.
T.R Neelakantan, N.V. Pundarikanthan, Neural Network-Based Simulation-Optimization Model for Reservoir Operation, Mar-Apr 2008, Journal of Water Resources Planning and Management
Summary:
The paper focuses on planning a model for reservoir operation which uses simulation-optimization approach. Author takes Chennai water supply as the study area. Reservoir planning was improved by demand management using the hedging rule which distributes the deficits for longer time by rationing water supply. For defining and optimizing the decision variables for hedging rule, the neural network based simulation model was used as a sub model to the Hookes and Jeeves programming model. Simulation analysis requires a operation policy, a standard policy is the optimal policy where the objective is to minimize the total deficit over the time. Hedging and rationing rule helps in distributing the deficit over a longer time. The total storage in the reservoir is divided into different zones and based on the falling level in each zone the release target can be fixed. For the study the reservoir is divided into four zones and the storage levels are S1, S2 and S3. This simulation model is sent as sub model to the Hookes and jeeves nonlinear programming model which passed management decision vectors to the simulation model to find the objective function as an output.
The whole study has been carried out in various stages. In the first stage the back propagation neural network is used to simulate the reservoir operation. Further in the second stage this neural network was fed as sub model to Hookes and Jeeves, this combined simulation-optimization model is used to screen the operation policies. In the third stage the best solution of the optimization is fine tuned using the conventional simulation-optimization model.
Authors have considered Chennai water supply as the study area. Chennai’s water supply is catered through three reservoirs- Poondi, Cholavaram and Red hills and ground water sources. The reservoirs are fed only by the north east monsoon which lasts only for three months. Due to increased extraction of ground water, the water table fell rapidly and there are traces of sea water intrusion. They have planned for the augmentation of the system by Krishna water. With the new excess water they have proposed to use Chembarambakkam reservoir as one of the terminal reservoirs. As Chennai is facing severe drought conditions the criteria would be to reduce the shortfalls as much as possible. During the drought condition the water supply managers prefer smaller shortfalls than dealing with larger ones and therefore they are following the method of hedging and rationing. Distribution of deficits should be done in such a way that they are spread for a longer period and with lesser magnitude. To do the above deficit index (sum of squared deficits) is followed which should be minimum among the other options. With the augmentation of Krishna water supply, equity of reservoir levels for two parallel reservoirs (Red Hills and Chembarambakkam) needs to be maintained. So the demand ratio needs to be 1:x and the deficit ratio to 1:x. As deficit index is the second order parameter the ratio between the two reservoirs needs to be 1:x^2.
The simulation model uses the mass balance principle and follows the constraints on canal capacity, minimum and maximum storage capacity, and evaporation loss and so on. The objective function is to minimize the deficit index by changing the decision management variables S1, S2, and S3 (Storage levels). The study was carried out using different scenarios considering different source and terminal reservoirs, to estimate which combination proves to improve the objective function. Inflow data into the reservoirs are studied to see the performance of the reservoir. Authors have considered catchment inflow, percolation loss, and transmission losses to be negligible. The study was carried out with different supply levels – full demand, 80% demand 75% demand, 67% demand and 50% demand.
Discussion:
This paper was interesting as the study deals with how we can optimize the operating policy based on the hedging rule. As this model is flexible to include various reservoirs and more complex system, I think it is a good model to carry out such a study. It has the flexibility of changing the nonlinear programming model instead of Hookes and Jeeves, which would be interesting to explore.
Monday, March 9, 2009
Assignment # 7
Article Reference:
Cristina Perez-Pedini, James F. Limbrunner, Richard M. Vogel, Optimization Location of Infiltration Based Best Management Practices for Storm Water Management, Nov-Dec 2008, Journal of Water Resources Planning and Management
Summary:
The present paper discusses about the optimization of infiltration based best management practices of Aberjona river watershed which is carried out by combination of hydrologic model and genetic algorithm. Main objective of the study was to optimize the number and location of infiltration based BMP thereby reducing the peak flow at the outlet of the watershed.
The hydrologic model was built using the SCS approach (CN method). This model was optimized using GA to find the areas within the watershed where the infiltration based BMP would be more effective to reduce the impacts of the increased peak flow. By considering different optimization results, the trade off curve between flood flow reduction and program budget. The paper considers the option of optimizing the BMP on the upslope so that it is more effective at the downstream flood protection. The whole catchment is modeled as the Hydrologic Response Units (HRU). It is considered that each HRU unit drains to nearest upslope HRU’s and a maximum HRU’s which can drain into are limited to 7. It is seen that only at most 2 HRU’s drain into adjacent upslope HRU. The stream network collects the runoff from the upstream HRU and routes to the watershed outlet. The hydrologic parameters were developed using ArcGIS and the cell to cell connectivity is done using D8 algorithm. BMP is modeled using a binary variable; introduction of BMP decreases the CN of the HRU. In the scope of this paper, they have assumed only the planning of the whole watershed system instead of designing of each BMP. We could further take the inputs from this methodology to study the watershed which have larger impact on the flood peak flow and apply the particular BMP to each HRU. The study considers only single type of BMP for the whole study as project cost would increase if different BMP types were considered. This study did not consider the cost implication of setting a BMP in HRU with different land use and surface conditions.
The hydrologic model is modified so that it calculated the cumulative water at the HRU by considering the sum of the precipitation, excess groundwater at the HRU and excess runoff from the adjacent down slope HRU and subtracting the cumulative initial abstraction. As defined by CN method, initial abstraction is defined as a fraction of the soil storage capacity. Combining above mentioned procedures, cumulative runoff, and cumulative infiltration are estimated. Ground water storage is calculated as sum of storage of previous time step, cumulative infiltration and sum of the previous time step base flow from the adjacent upslope. Stream channel is routed to carry the runoff and the base flow to the watershed outlet with a time lag. One of the model disadvantages is that time step is considered to be the major control of the system, so the time step needs to be calibrated such that it meets both the peak of flow and the basin lag time.
The hydrologic model was calibrated using the observed and modeled hydrograph. The model could not be used to model long term recession which impacts the groundwater storage and characteristics of the outflow. The objective of the study was to choose the HRU where if BMP applied would reduce the peak flow at the watershed outlet. As only one type of BMP is considered therefore project cost is directly proportional to the number of BMP selected. The study used GA approach to analyze different groups of BMP location so that the peak flow of a October storm is reduced. Initially every HRU was considered to be having BMP which was found out to be infeasible, so they restricted the location of BMP based on the CN which targets the HRU which is more impervious and which will eventually cause more runoff into the stream network. GA was used to maximize the peak flow reduction for a given budget constraint that total number of BMPs selected should not exceed than that of the preselected.
By continuous optimization with varied number of BMP’s i.e varied costs, a tradeoff (Pareto frontier) curve was obtained between the cost and the peak flow reduction. All the solutions below this curve are feasible and all the solutions above the curve as infeasible. The paper recommends for a distributed physical representation of the basin for carrying out BMP planning analysis. It was concluded that for the present area of study by applying BMP at not less than 200 HRU we can achieve 20% reduction in peak flow. It is illustrated by the trade off curve that with the increase in the number of BMP’s the returns are decreased. Author suggests using the incremental approach in designing which is BMP is introduced at places which are most affected by the storm and then moving on to the places which aren’t that critical, such an approach would be helpful in targeting resource management.
Discussion:
The paper was very helpful in giving an insight of how the GA optimization could be carried out. As the authors specify that physical representation of the basin is required for the planning, taking up a research to study that and comparing the results with this model which did not take into the consideration without a physical model would be worth knowing. The other aspect would be considering how the cost optimization results will be affected by considering different BMP’s based on the land use pattern of each HRU.
Cristina Perez-Pedini, James F. Limbrunner, Richard M. Vogel, Optimization Location of Infiltration Based Best Management Practices for Storm Water Management, Nov-Dec 2008, Journal of Water Resources Planning and Management
Summary:
The present paper discusses about the optimization of infiltration based best management practices of Aberjona river watershed which is carried out by combination of hydrologic model and genetic algorithm. Main objective of the study was to optimize the number and location of infiltration based BMP thereby reducing the peak flow at the outlet of the watershed.
The hydrologic model was built using the SCS approach (CN method). This model was optimized using GA to find the areas within the watershed where the infiltration based BMP would be more effective to reduce the impacts of the increased peak flow. By considering different optimization results, the trade off curve between flood flow reduction and program budget. The paper considers the option of optimizing the BMP on the upslope so that it is more effective at the downstream flood protection. The whole catchment is modeled as the Hydrologic Response Units (HRU). It is considered that each HRU unit drains to nearest upslope HRU’s and a maximum HRU’s which can drain into are limited to 7. It is seen that only at most 2 HRU’s drain into adjacent upslope HRU. The stream network collects the runoff from the upstream HRU and routes to the watershed outlet. The hydrologic parameters were developed using ArcGIS and the cell to cell connectivity is done using D8 algorithm. BMP is modeled using a binary variable; introduction of BMP decreases the CN of the HRU. In the scope of this paper, they have assumed only the planning of the whole watershed system instead of designing of each BMP. We could further take the inputs from this methodology to study the watershed which have larger impact on the flood peak flow and apply the particular BMP to each HRU. The study considers only single type of BMP for the whole study as project cost would increase if different BMP types were considered. This study did not consider the cost implication of setting a BMP in HRU with different land use and surface conditions.
The hydrologic model is modified so that it calculated the cumulative water at the HRU by considering the sum of the precipitation, excess groundwater at the HRU and excess runoff from the adjacent down slope HRU and subtracting the cumulative initial abstraction. As defined by CN method, initial abstraction is defined as a fraction of the soil storage capacity. Combining above mentioned procedures, cumulative runoff, and cumulative infiltration are estimated. Ground water storage is calculated as sum of storage of previous time step, cumulative infiltration and sum of the previous time step base flow from the adjacent upslope. Stream channel is routed to carry the runoff and the base flow to the watershed outlet with a time lag. One of the model disadvantages is that time step is considered to be the major control of the system, so the time step needs to be calibrated such that it meets both the peak of flow and the basin lag time.
The hydrologic model was calibrated using the observed and modeled hydrograph. The model could not be used to model long term recession which impacts the groundwater storage and characteristics of the outflow. The objective of the study was to choose the HRU where if BMP applied would reduce the peak flow at the watershed outlet. As only one type of BMP is considered therefore project cost is directly proportional to the number of BMP selected. The study used GA approach to analyze different groups of BMP location so that the peak flow of a October storm is reduced. Initially every HRU was considered to be having BMP which was found out to be infeasible, so they restricted the location of BMP based on the CN which targets the HRU which is more impervious and which will eventually cause more runoff into the stream network. GA was used to maximize the peak flow reduction for a given budget constraint that total number of BMPs selected should not exceed than that of the preselected.
By continuous optimization with varied number of BMP’s i.e varied costs, a tradeoff (Pareto frontier) curve was obtained between the cost and the peak flow reduction. All the solutions below this curve are feasible and all the solutions above the curve as infeasible. The paper recommends for a distributed physical representation of the basin for carrying out BMP planning analysis. It was concluded that for the present area of study by applying BMP at not less than 200 HRU we can achieve 20% reduction in peak flow. It is illustrated by the trade off curve that with the increase in the number of BMP’s the returns are decreased. Author suggests using the incremental approach in designing which is BMP is introduced at places which are most affected by the storm and then moving on to the places which aren’t that critical, such an approach would be helpful in targeting resource management.
Discussion:
The paper was very helpful in giving an insight of how the GA optimization could be carried out. As the authors specify that physical representation of the basin is required for the planning, taking up a research to study that and comparing the results with this model which did not take into the consideration without a physical model would be worth knowing. The other aspect would be considering how the cost optimization results will be affected by considering different BMP’s based on the land use pattern of each HRU.
Monday, March 2, 2009
Assignment # 66
Article Reference:
Pradeep Kumar Behera, Fabian Papa, Barry J. Adams, Optimization of Regional Storm Water Management Systems, 1999, Journal of Water Resources Planning and Management
Summary:
The paper focuses on the optimization methodology to determine the detention pond storage volume, release rate and pond depth for a single storm management pond, to meet the environmental regulations of runoff quality and quantity. The above mentioned methodology was extended to evaluate the storm management parameter for multiple catchments using dynamic programming.
With the increase in urbanization the importance of dealing with the uncontrolled discharge of runoff which results in adverse impacts like bank erosion, flooding and increasing the chances of pollution. Best management practices (BMP) are considered to attenuate the peak flow, control the runoff volume and control runoff quality, so as to maintain the predevelopment runoff conditions or meet the environmental regulations for runoff quality and quantity. The present study focuses on using detention pond as the storm management control measure. Volume and quality of runoff controlled is largely dependent on the storage volume of the detention pond. Though Storm water management pond (detention pond) is considered as the measure to mitigate the adverse effects, land developers and municipalities consider such ponds to be loss of developable land and added cost of construction and maintenance. The objective of such developers is to minimize the cost associated to the SWM ponds with satisfying the environmental regulations. Typical cost of concerns associated to these SWM ponds are cost of land occupied by the ponds, operation, maintenance and repair (OMR) costs. The present study is to optimize the geometry of the SWM pond to meet the runoff volume control and pollution control to a single catchment, further the problem was formulated for a multiple catchments to optimize design the parameters such that they meet the overall runoff control and pollution control.
The model was formulated considering three parallel catchments having similar metrological characteristics and with SWM ponds which are located upstream of the outlet into the common collection system. Different levels of quality and quantity control was considered at different catchments such that the final or overall control of quality and quantity at the outfall was met according to the environmental regulations. By considering the above mentioned methodology it will be easy to optimize the solution for minimizing the cost of implementing the SWM ponds for all the catchments by providing optimal blend of individual catchments controls than considered uniform control. Both runoff quantity and quality control constraint at the outfall are considered to be greater than the area-weighted average level of pollution/volume control at each catchment. In the study they have not considered the local conveyance cost as normally the SWM ponds are situated in close proximity to the collection system and they did not consider differential cost associated to different rates of release from the pond. In the present work, SWM ponds is considered to be extended detention dry pond type which stores catchment runoff until the entire volume is used. Decision variable in the optimization of the problem are the storage volume, release rate and the pond depth which estimates the extent of runoff quantity and quality.
For carrying out optimizing of SWM pond in a single catchment they have considered 90% runoff control isoquant and 50% pollution control isoquant with constant pond depth to study the strategy of how the release rates and storage volume of the pond vary. As pond depth is also a decision variable in optimizing the solution, a range of depths are analyzed to produce corresponding optimal storage volume and release rates. Therefore by considering the relationship between pond cost and pond depth, an optimal pond depth is estimated which meets the pollution and runoff control constraints.
For optimizing a SWM pond for multiple catchments, DP is considered as the optimization tool which divides the multiple catchment problem into series of individual problems, then combining the solution of each small(stages) problem to the overall (multiple catchment) problem. Overall pollution and runoff control is not violated even if we decompose the model into simpler stages. After the computation of each stage is carried out, track back procedure is followed to find the least cost of the SWM pond considering the design variables.
Discussion:
I found the paper very informative as it gives an idea on how a single catchment SWM optimization and multiple catchment optimizations are done. I could not find any particular problem of concern. But it would be interesting to carry out further research by considering all the assumptions they made in the present study.
Pradeep Kumar Behera, Fabian Papa, Barry J. Adams, Optimization of Regional Storm Water Management Systems, 1999, Journal of Water Resources Planning and Management
Summary:
The paper focuses on the optimization methodology to determine the detention pond storage volume, release rate and pond depth for a single storm management pond, to meet the environmental regulations of runoff quality and quantity. The above mentioned methodology was extended to evaluate the storm management parameter for multiple catchments using dynamic programming.
With the increase in urbanization the importance of dealing with the uncontrolled discharge of runoff which results in adverse impacts like bank erosion, flooding and increasing the chances of pollution. Best management practices (BMP) are considered to attenuate the peak flow, control the runoff volume and control runoff quality, so as to maintain the predevelopment runoff conditions or meet the environmental regulations for runoff quality and quantity. The present study focuses on using detention pond as the storm management control measure. Volume and quality of runoff controlled is largely dependent on the storage volume of the detention pond. Though Storm water management pond (detention pond) is considered as the measure to mitigate the adverse effects, land developers and municipalities consider such ponds to be loss of developable land and added cost of construction and maintenance. The objective of such developers is to minimize the cost associated to the SWM ponds with satisfying the environmental regulations. Typical cost of concerns associated to these SWM ponds are cost of land occupied by the ponds, operation, maintenance and repair (OMR) costs. The present study is to optimize the geometry of the SWM pond to meet the runoff volume control and pollution control to a single catchment, further the problem was formulated for a multiple catchments to optimize design the parameters such that they meet the overall runoff control and pollution control.
The model was formulated considering three parallel catchments having similar metrological characteristics and with SWM ponds which are located upstream of the outlet into the common collection system. Different levels of quality and quantity control was considered at different catchments such that the final or overall control of quality and quantity at the outfall was met according to the environmental regulations. By considering the above mentioned methodology it will be easy to optimize the solution for minimizing the cost of implementing the SWM ponds for all the catchments by providing optimal blend of individual catchments controls than considered uniform control. Both runoff quantity and quality control constraint at the outfall are considered to be greater than the area-weighted average level of pollution/volume control at each catchment. In the study they have not considered the local conveyance cost as normally the SWM ponds are situated in close proximity to the collection system and they did not consider differential cost associated to different rates of release from the pond. In the present work, SWM ponds is considered to be extended detention dry pond type which stores catchment runoff until the entire volume is used. Decision variable in the optimization of the problem are the storage volume, release rate and the pond depth which estimates the extent of runoff quantity and quality.
For carrying out optimizing of SWM pond in a single catchment they have considered 90% runoff control isoquant and 50% pollution control isoquant with constant pond depth to study the strategy of how the release rates and storage volume of the pond vary. As pond depth is also a decision variable in optimizing the solution, a range of depths are analyzed to produce corresponding optimal storage volume and release rates. Therefore by considering the relationship between pond cost and pond depth, an optimal pond depth is estimated which meets the pollution and runoff control constraints.
For optimizing a SWM pond for multiple catchments, DP is considered as the optimization tool which divides the multiple catchment problem into series of individual problems, then combining the solution of each small(stages) problem to the overall (multiple catchment) problem. Overall pollution and runoff control is not violated even if we decompose the model into simpler stages. After the computation of each stage is carried out, track back procedure is followed to find the least cost of the SWM pond considering the design variables.
Discussion:
I found the paper very informative as it gives an idea on how a single catchment SWM optimization and multiple catchment optimizations are done. I could not find any particular problem of concern. But it would be interesting to carry out further research by considering all the assumptions they made in the present study.
Monday, February 23, 2009
Assignment # 5
Article Reference:
Jonathan W. Berry, Lisa Fleischer, William E. Hart, Cynthia A. Philips, Jean Paul Watson, Sensor Placement in Municipal Water Networks, 2005, Journal of Water Resources Planning and Management
Summary:
The paper presents a model for optimizing the locations of the sensors in the municipal water networks for detecting the injected contaminants using the mixed integer program.
As already studied, the importance of estimating the water quality in the distribution system is essential, therefore placement of the sensor in the water system is of greater importance. The recent concerns of the terrorist attacks may affect the public belief on the water supplies. Therefore EPA is working with various community water systems towards water safety and security, real-time early warning systems (EWS) is one of the methods to monitor and identify any unusual threat the water supply system thereby getting appropriate time to handle the adverse impacts. EWS still uses conventional water quality monitoring which considers the changes in a specific water quality parameter to infer the presence of a contaminant. There are many issues regarding usage of EWS which needs to be researched yet.
The present study is carried out to deploy a sensor within a water distribution system. An effective deployment of sensor would take into consideration the maximum coverage of the network for the monitoring of the contamination. To optimize the location of the sensor there main objective would be to minimize the cost of the deployment and maximize the coverage of the sensor. But such sensors would not provide warning of the initial contamination. Present paper focuses on the optimization of the sensor placement based on minimizing the fraction of population being affected by the contaminants. Contamination across the network is modeled as the probability distribution across the junctions. Paper takes two synthetic data sets and one real time example to illustrate the placement of sensors.
Authors have made few simplified assumptions which ignore temporal effects, concentration effects and health impacts therefore this model may be more suited to the system where large volume of contaminant flow rapidly through the network. In the studies carried out earlier they have modeled the placement of sensors based on demand coverage, volume of the contamination and contamination time, the present study models the system considering the fraction of the population who are going to be effected by the contamination in the system. System is modeled as a single point attack. As the location of the attack is just an assumption therefore the sensors are places based on set of weighted attack scenarios. Demand in the system is assumed to be of a fixed set of pattern and the water flow analysis is carried out using EPANET. As we have seen in Lee and Deininger each node is considered as the fraction of the total demand, here we consider each node to be the fraction of population being affected. The population considered is not based on the demand. All the attack scenarios are defined as the probability distribution which is based on the expert opinions.
The model is optimized based on mixed integer programming (MIP) which minimizes the total population being affected by the contamination. Different constraints considered are (1) if the node is attacked directly then it is contaminated, (2) a single sensor covers the flow in both the directions (3) About contamination propagation (4) limit of the total number of sensors.
The authors carried out the optimization of sensor placement on the two data set examples from EPANET and the real world data set. The study is carried by dividing the total system into different categories, considering different attack scenarios, flow patterns and limiting the availability of the sensors. The study was majorly concentrating on how the uncertainties in data, population densities and attack risks affect the optimal solutions and optimal location of the sensors in the system. For studying the affect of the uncertainties in the solution, they have modeled the problem using different set of noise levels where they have considered different values for each element of population density and the risk probabilities, which sum up to total population and risk probability summing to 1. The optimal sensor configuration is based on the distance measure between two sensors; this is compared with the baseline (no noise level). The distance is defined as the number of nodes which are covered with shortest path between the two pipes in the network. The authors illustrated how the uncertainties do not have much of an effect on the optimal sensor placement and the configuration.
Discussion:
With the previous paper which discusses on the methodology of how we can optimize the location of the sensor, this paper gives more insight into the topic by explaining different assumptions, variable and constraints involves, and sensitivity analysis carried out which might affect the solution. The assumption of considering only one set of flow pattern according to me might not be the real world problem. As different distribution systems have different flow patterns and different source of supply. It would be interesting to do research on how multiple attack points be modeled and optimized. In the present study they have considered the cost or total number of sensors, as the one of the constraint, considering about how the optimal solution may alter if we considers time as the main constraint, which means we model the problem in a way that we require the contamination detection or source identification within a given time limit.
Jonathan W. Berry, Lisa Fleischer, William E. Hart, Cynthia A. Philips, Jean Paul Watson, Sensor Placement in Municipal Water Networks, 2005, Journal of Water Resources Planning and Management
Summary:
The paper presents a model for optimizing the locations of the sensors in the municipal water networks for detecting the injected contaminants using the mixed integer program.
As already studied, the importance of estimating the water quality in the distribution system is essential, therefore placement of the sensor in the water system is of greater importance. The recent concerns of the terrorist attacks may affect the public belief on the water supplies. Therefore EPA is working with various community water systems towards water safety and security, real-time early warning systems (EWS) is one of the methods to monitor and identify any unusual threat the water supply system thereby getting appropriate time to handle the adverse impacts. EWS still uses conventional water quality monitoring which considers the changes in a specific water quality parameter to infer the presence of a contaminant. There are many issues regarding usage of EWS which needs to be researched yet.
The present study is carried out to deploy a sensor within a water distribution system. An effective deployment of sensor would take into consideration the maximum coverage of the network for the monitoring of the contamination. To optimize the location of the sensor there main objective would be to minimize the cost of the deployment and maximize the coverage of the sensor. But such sensors would not provide warning of the initial contamination. Present paper focuses on the optimization of the sensor placement based on minimizing the fraction of population being affected by the contaminants. Contamination across the network is modeled as the probability distribution across the junctions. Paper takes two synthetic data sets and one real time example to illustrate the placement of sensors.
Authors have made few simplified assumptions which ignore temporal effects, concentration effects and health impacts therefore this model may be more suited to the system where large volume of contaminant flow rapidly through the network. In the studies carried out earlier they have modeled the placement of sensors based on demand coverage, volume of the contamination and contamination time, the present study models the system considering the fraction of the population who are going to be effected by the contamination in the system. System is modeled as a single point attack. As the location of the attack is just an assumption therefore the sensors are places based on set of weighted attack scenarios. Demand in the system is assumed to be of a fixed set of pattern and the water flow analysis is carried out using EPANET. As we have seen in Lee and Deininger each node is considered as the fraction of the total demand, here we consider each node to be the fraction of population being affected. The population considered is not based on the demand. All the attack scenarios are defined as the probability distribution which is based on the expert opinions.
The model is optimized based on mixed integer programming (MIP) which minimizes the total population being affected by the contamination. Different constraints considered are (1) if the node is attacked directly then it is contaminated, (2) a single sensor covers the flow in both the directions (3) About contamination propagation (4) limit of the total number of sensors.
The authors carried out the optimization of sensor placement on the two data set examples from EPANET and the real world data set. The study is carried by dividing the total system into different categories, considering different attack scenarios, flow patterns and limiting the availability of the sensors. The study was majorly concentrating on how the uncertainties in data, population densities and attack risks affect the optimal solutions and optimal location of the sensors in the system. For studying the affect of the uncertainties in the solution, they have modeled the problem using different set of noise levels where they have considered different values for each element of population density and the risk probabilities, which sum up to total population and risk probability summing to 1. The optimal sensor configuration is based on the distance measure between two sensors; this is compared with the baseline (no noise level). The distance is defined as the number of nodes which are covered with shortest path between the two pipes in the network. The authors illustrated how the uncertainties do not have much of an effect on the optimal sensor placement and the configuration.
Discussion:
With the previous paper which discusses on the methodology of how we can optimize the location of the sensor, this paper gives more insight into the topic by explaining different assumptions, variable and constraints involves, and sensitivity analysis carried out which might affect the solution. The assumption of considering only one set of flow pattern according to me might not be the real world problem. As different distribution systems have different flow patterns and different source of supply. It would be interesting to do research on how multiple attack points be modeled and optimized. In the present study they have considered the cost or total number of sensors, as the one of the constraint, considering about how the optimal solution may alter if we considers time as the main constraint, which means we model the problem in a way that we require the contamination detection or source identification within a given time limit.
Monday, February 16, 2009
Assignment # 4
Article Reference:
Byoung Ho Lee, Rolf A Deininger, January/February 2009, Optimal Locations of Monitoring Stations in Water Distribution System, Journal of Environmental Engineering
Summary:
US Environmental Protection Agency requires all the drinking water authorities to meet the drinking water quality standards in the distribution system. There are a set of regulations for selecting the monitoring locations, sampling frequency and the different water quality parameters to be monitored. For setting up a monitoring station, flow, flow pattern and pressures in the system need to be determined which is done using different hydraulic models. The paper describes about the methods of how to choose the monitoring stations thereby maximizing the coverage. Author explains how this problem was solved using the integer programming.
Author illustrates a small example. In the example the water fractions of each node were calculated and it is summarized in the matrix W, which shows how each node contributes to the sampling station. Based on the W matrix a knowledge based matrix K is derived which shows the decision of which node to be considered as the covered. Coverage criteria are selected to base the selection of the covered node. For this particular example they have considered 50%, which means the selected covered node should pass through at least 50% of the sampled water. Coverage matrix is obtained from the K, by converting all the non zero entries to ones in the matrix. Optimizing function of the problem can be formulated like below, where d=demand at the node, y=set which denotes if the demand at this node is covered, x=sampling station at node and a= transpose of the Matrix K.
One more example was considered for locating the monitoring stations in a medium sized city like Flint, Michigan. The city gets its supply from Huron River through a pipeline operated by Detroit Water and Sewerage board. The treated water is channelized through the pipeline till the location of original treatment plant which is not in use any more. As of now there are total of 14 monitoring stations which cover about 18.3% of total demand. For finding out the optimal solution of location of monitoring station first hydraulic analysis was carried out using COVER which formulates the coverage matrix W. COVTOIP is used to convert the coverage matrix to standard input file for IP package. It was found that after optimization total coverage was found to be 54%, when compared to 18.3% previously. As this was considered for only one scenario, author explains about how to handle the multiple scenarios situation. When considering multiple flow scenarios we need to take into account flow pattern which change based on hourly, daily or seasonal. By considering different demand patters, and the maximum coverage percentage to be achieved, the objective function and constraints are formulated which are then used to final an optimal solution. In similar grounds, an example of optimizing the location of monitoring stations for Cheshire city in Connecticut. By considering different flow patterns, different options of monitoring stations were found out. Final stations were selected based on the coverage percentage.
Discussion:
As of now as there are no guidelines for selecting the monitoring stations, combination of pathway analysis, coverage matrices and integer programming provides a first step for landing up at the monitoring stations. However for the large networks this method was very difficult to handle because of the large dimensionality of the problem. Further studies were carried out based on the methodology as proposed by Lee and Deininger one of them was by Muhammed and Khurram who tried to optimize the solution using Genetic Algorithm.
The article was very interesting as it gave an insight about how the monitoring stations are selected for finding out the water quality in the distribution system. Few of the points which was not clear was about how did they land with the assumption of taking 50% of coverage. How well can this are taken into consideration in other type of problems (cities). If this was my research topic I would like to explore how the location of the station might vary by considering different optimization techniques. Would like to to explore how such a technique be used to solve the problem for a big distribution system.
Byoung Ho Lee, Rolf A Deininger, January/February 2009, Optimal Locations of Monitoring Stations in Water Distribution System, Journal of Environmental Engineering
Summary:
US Environmental Protection Agency requires all the drinking water authorities to meet the drinking water quality standards in the distribution system. There are a set of regulations for selecting the monitoring locations, sampling frequency and the different water quality parameters to be monitored. For setting up a monitoring station, flow, flow pattern and pressures in the system need to be determined which is done using different hydraulic models. The paper describes about the methods of how to choose the monitoring stations thereby maximizing the coverage. Author explains how this problem was solved using the integer programming.
Author illustrates a small example. In the example the water fractions of each node were calculated and it is summarized in the matrix W, which shows how each node contributes to the sampling station. Based on the W matrix a knowledge based matrix K is derived which shows the decision of which node to be considered as the covered. Coverage criteria are selected to base the selection of the covered node. For this particular example they have considered 50%, which means the selected covered node should pass through at least 50% of the sampled water. Coverage matrix is obtained from the K, by converting all the non zero entries to ones in the matrix. Optimizing function of the problem can be formulated like below, where d=demand at the node, y=set which denotes if the demand at this node is covered, x=sampling station at node and a= transpose of the Matrix K.
One more example was considered for locating the monitoring stations in a medium sized city like Flint, Michigan. The city gets its supply from Huron River through a pipeline operated by Detroit Water and Sewerage board. The treated water is channelized through the pipeline till the location of original treatment plant which is not in use any more. As of now there are total of 14 monitoring stations which cover about 18.3% of total demand. For finding out the optimal solution of location of monitoring station first hydraulic analysis was carried out using COVER which formulates the coverage matrix W. COVTOIP is used to convert the coverage matrix to standard input file for IP package. It was found that after optimization total coverage was found to be 54%, when compared to 18.3% previously. As this was considered for only one scenario, author explains about how to handle the multiple scenarios situation. When considering multiple flow scenarios we need to take into account flow pattern which change based on hourly, daily or seasonal. By considering different demand patters, and the maximum coverage percentage to be achieved, the objective function and constraints are formulated which are then used to final an optimal solution. In similar grounds, an example of optimizing the location of monitoring stations for Cheshire city in Connecticut. By considering different flow patterns, different options of monitoring stations were found out. Final stations were selected based on the coverage percentage.
Discussion:
As of now as there are no guidelines for selecting the monitoring stations, combination of pathway analysis, coverage matrices and integer programming provides a first step for landing up at the monitoring stations. However for the large networks this method was very difficult to handle because of the large dimensionality of the problem. Further studies were carried out based on the methodology as proposed by Lee and Deininger one of them was by Muhammed and Khurram who tried to optimize the solution using Genetic Algorithm.
The article was very interesting as it gave an insight about how the monitoring stations are selected for finding out the water quality in the distribution system. Few of the points which was not clear was about how did they land with the assumption of taking 50% of coverage. How well can this are taken into consideration in other type of problems (cities). If this was my research topic I would like to explore how the location of the station might vary by considering different optimization techniques. Would like to to explore how such a technique be used to solve the problem for a big distribution system.
Monday, February 9, 2009
Assignment # 3
Article Reference:
Garrett Hardin, The tragedy of the Commons, Science, 162(1968):1243-1248
The author tries to focus on the kind of conclusion which is drawn in few of problems saying there is no technical solution and that few of the human problems fall into this category. Author explains technical solution as‘ one that requires a change only in the techniques of the natural science, demanding little or nothing in the way of change in human values or ideas of mortality. Population problem is considered to be one of the members of the class ‘no technical solution problem. Author highlights that this problem does not have a technical solution; therefore to avoid the future practical problems it is essential to consider that world available to terrestrial human population is finite. As finite world can support only finite population, the population growth should tend to zero. It will not have one solution for the problem as the perspective of seeing the problem, its effects and its advantages differ from individual to individual. Therefore for the years ahead it is desirable to estimate the acceptable theory of weighing the problem, summarizing the effects, and estimating the non linear variation of the problem.
According to the conclusions laid down by Adam Smith, all the decisions which reach the individual will in fact be the decision made for the entire society. Each individual pursues his best interest to explore the freedom of the commons so as to maximize his profit which eventually brings ruin to all. Each man is locked up in the system which forces him to increase his usage of the commons without the limit, in a world that is limited. Individual benefits through the denial of the truth of how the freedom of commons is affecting the society as a whole around him. Author refers to this as the “Tragedy of Freedom in a commons”. Author illustrates the example of the National park working out with the tragedy of commons. National park being limited in extent where as with the increase in population there is a threat of destruction of the commons. Therefore it is necessary to come up with laws which safeguard the commons, though they seem to be objectionable, it ought be followed to stop the destruction or extinction of the existing resources/commons.
Tragedy of commons reappears in the pollution problem. Every individual assumes that his share of waste discharging into the waste is less that the total cost of purifying the wastes before releasing them. Thereby author states that ‘we are all locked into a system of fouling our own nest so long as we behave only as independent, rational, free-enterprisers’. Few of the commons cannot be fenced so they need to be prevented using different means like making laws, policies or taxing devises. Author recommends the concept of private property which would help us from exhausting the earth’s resources. The above mentioned problem is one of the consequences of the population growth. Author explains that things got worse with change in time, as the population got denser the pollution increased thereby requesting for redefinition of property rights.
Author lays emphasis on seeing the problem as the function of the state of system at the time it is performed. We could never realize the effects of an act unless we see the whole system in which the act appears. Author explains that even now the laws followed by people are origin of ancient society which would not be capable of handling complex, crowded and changeable world so there is a shear importance of changing the pattern of the laws which would take into consideration the complexity of the problems. The main challenge ahead of us is to find ways to legitimate the body that makes laws so they are liable to corruption. If each family was dependent on its own resources then there would be no public interest of controlling the breeding. As we being the welfare state we believe in giving equal rights of commons to all the individuals there by leading to the tragic course of action. Author explains that if we believe in the truth of freedom to breed is intolerable and is a threat to the commons extinction then we need to openly deny the validity of the statement of Universal Declaration of Human Rights, according to them the size of the family should be the decision of the family itself and not of anyone else.
Author highlights that it would be a mistake assuming that we can control the breeding in future by appealing to the conscience. As people vary, therefore this kind of confrontation of limiting the size of the family would obviously make people having greater family size to plea against the confrontation. Author refers to having a system which works towards the goal. Expecting results on basis of eliminating or restraining individual from exploiting the commons needs to be checked with regard to the pathogenic effects of conscience.
Leaders in the highest level surrender to the temptation of extending the control over the legal limits with respect to conjuring the conscience in others. It is always being witnessed that when there is a plea of responsibility towards a social arrangement it will eventually create coercion of some sort. Therefore it is always recommended that a mutual coercion needs to be agreed upon by majority of the people who are being affected by it. For example everyone complains about the compulsory taxes but then everyone recognizes that this would favor in improving the few of the commons.
Vital aspect which needs to be acted upon is to stop the commons in breeding, as there is no technical solution which can help us from the impacts of over population. For the moment, to avoid the compelled decision we are persuading about the conscience and responsible parenthood. An individual appeal will disappear in the long run there by increasing the anxiety of dealing with the tragedy of commons. The only way we can deal and this tragedy of commons is to forgo the freedom of breed.
Garrett Hardin, The tragedy of the Commons, Science, 162(1968):1243-1248
The author tries to focus on the kind of conclusion which is drawn in few of problems saying there is no technical solution and that few of the human problems fall into this category. Author explains technical solution as‘ one that requires a change only in the techniques of the natural science, demanding little or nothing in the way of change in human values or ideas of mortality. Population problem is considered to be one of the members of the class ‘no technical solution problem. Author highlights that this problem does not have a technical solution; therefore to avoid the future practical problems it is essential to consider that world available to terrestrial human population is finite. As finite world can support only finite population, the population growth should tend to zero. It will not have one solution for the problem as the perspective of seeing the problem, its effects and its advantages differ from individual to individual. Therefore for the years ahead it is desirable to estimate the acceptable theory of weighing the problem, summarizing the effects, and estimating the non linear variation of the problem.
According to the conclusions laid down by Adam Smith, all the decisions which reach the individual will in fact be the decision made for the entire society. Each individual pursues his best interest to explore the freedom of the commons so as to maximize his profit which eventually brings ruin to all. Each man is locked up in the system which forces him to increase his usage of the commons without the limit, in a world that is limited. Individual benefits through the denial of the truth of how the freedom of commons is affecting the society as a whole around him. Author refers to this as the “Tragedy of Freedom in a commons”. Author illustrates the example of the National park working out with the tragedy of commons. National park being limited in extent where as with the increase in population there is a threat of destruction of the commons. Therefore it is necessary to come up with laws which safeguard the commons, though they seem to be objectionable, it ought be followed to stop the destruction or extinction of the existing resources/commons.
Tragedy of commons reappears in the pollution problem. Every individual assumes that his share of waste discharging into the waste is less that the total cost of purifying the wastes before releasing them. Thereby author states that ‘we are all locked into a system of fouling our own nest so long as we behave only as independent, rational, free-enterprisers’. Few of the commons cannot be fenced so they need to be prevented using different means like making laws, policies or taxing devises. Author recommends the concept of private property which would help us from exhausting the earth’s resources. The above mentioned problem is one of the consequences of the population growth. Author explains that things got worse with change in time, as the population got denser the pollution increased thereby requesting for redefinition of property rights.
Author lays emphasis on seeing the problem as the function of the state of system at the time it is performed. We could never realize the effects of an act unless we see the whole system in which the act appears. Author explains that even now the laws followed by people are origin of ancient society which would not be capable of handling complex, crowded and changeable world so there is a shear importance of changing the pattern of the laws which would take into consideration the complexity of the problems. The main challenge ahead of us is to find ways to legitimate the body that makes laws so they are liable to corruption. If each family was dependent on its own resources then there would be no public interest of controlling the breeding. As we being the welfare state we believe in giving equal rights of commons to all the individuals there by leading to the tragic course of action. Author explains that if we believe in the truth of freedom to breed is intolerable and is a threat to the commons extinction then we need to openly deny the validity of the statement of Universal Declaration of Human Rights, according to them the size of the family should be the decision of the family itself and not of anyone else.
Author highlights that it would be a mistake assuming that we can control the breeding in future by appealing to the conscience. As people vary, therefore this kind of confrontation of limiting the size of the family would obviously make people having greater family size to plea against the confrontation. Author refers to having a system which works towards the goal. Expecting results on basis of eliminating or restraining individual from exploiting the commons needs to be checked with regard to the pathogenic effects of conscience.
Leaders in the highest level surrender to the temptation of extending the control over the legal limits with respect to conjuring the conscience in others. It is always being witnessed that when there is a plea of responsibility towards a social arrangement it will eventually create coercion of some sort. Therefore it is always recommended that a mutual coercion needs to be agreed upon by majority of the people who are being affected by it. For example everyone complains about the compulsory taxes but then everyone recognizes that this would favor in improving the few of the commons.
Vital aspect which needs to be acted upon is to stop the commons in breeding, as there is no technical solution which can help us from the impacts of over population. For the moment, to avoid the compelled decision we are persuading about the conscience and responsible parenthood. An individual appeal will disappear in the long run there by increasing the anxiety of dealing with the tragedy of commons. The only way we can deal and this tragedy of commons is to forgo the freedom of breed.
Monday, February 2, 2009
Assignment # 2
Article Reference:
Dorothy Fisher Atwood, Steven M. Gorelick, Hydraulic Gradient Control for Ground Water Contaminant Removal, 1985, Journal of Hydrology
Summary:
The paper explains about how linear programming can be used in optimizing the well location and recharging/pumping schedules so as to minimize total pumping and recharge. The planning procedure comprises of two stages, first to simulate the ground water flow and solute transport model and study the removal of contaminant under the assumed velocity; secondly the analyze the model with the relevant constraints and objectives is fed into the linear program for finding out the optimized solution.
In view of the increase of groundwater pollution incidents, aquifer planning and restoring has become of great interest. The present paper illustrates the methodology of controlling the hydraulic gradient for removal of the contaminants from the groundwater. Initially one of the techniques used for groundwater management as considered by Molz and Bell (1977) was using embedding systems method, in which the constraints for the linear model included are groundwater flow equation, pumping rates and hydraulic gradients. But this technique was limited to using for small steady state flow problems. Further Remson and Gorelick (1980) applied embedded systems approach to identify the well location and rates to prevent the contaminant plume from migrating. Another technique in groundwater modeling is response matrix which is used in conjunction with linear and quadratic programming to find out the optimizing solution to maximize the well yields and minimizing the production cost.
The Rocky Mountain Arsenal near Denver, Colorado, U.S.A which was the military facility to manufacture and process toxic chemicals for military and industrial use. This area has a history of groundwater contamination because of the poor disposal techniques. For carrying out the study, model area (about 3 km2) considered is the north boundary of the Rocky Mountain Arsenal, as the flow in the unconfined aquifer is from south to north; therefore goal of the design is to prevent further migration of contaminant during the aquifer cleanup. The model area was discretized into 702 finite difference nodes approximating the boundaries. South west flux boundary was calculated by running the steady state simulation, constant north head boundary was based on the water levels, Western and eastern boundaries are represented as no-flow boundaries. The parameters of hydro-geologic considered in the study are derived from the groundwater and solute transport models.
The hydraulic gradient control design procedure comprises of two design stages. In stage I, simulation of solute transport is used to locate the shrinking plume boundary. For locating the plume boundary with respect to the potential gradient control wells, the contaminant transport is simulated through time and using an assumed velocity field. To reduce the contamination level to safe level the following factors play main role; number of wells, location and pumping rates of the contaminant removal wells. By trial and error most effective location of the well was selected which would restore the water quality of the groundwater more effectively. With the found well location study of plume boundary reduction over the years was carried out. It was found that with the selected well location the entire plume can be removed in over 12 years. This geometry of the plume if further considered for carrying out stage II.
In stage II, linear programming combined with ground water flow simulation is used to find out optimum well location and pumping/recharge rates are estimated which would minimize the migration of the plume by controlling the hydraulic gradient. Objective function of the problem would be minimizing the pumping and recharging rate of the well for the management period of 32 pumping periods, constraints would be the hydraulic gradient control which will have decision variables associated with pumping and recharging.
There are two different solution strategies considered in the study of the project area. Sequential strategy uses series of sequential optimization for each pumping period. On the other hand single global optimization uses for total 32 pumping periods. Though the pumping/recharge rates are comparable between the two strategies, well selection and schedules of pumping are different. It was observed that cumulative pumping/recharge rates of global optimization was about 10% better than sequential solution over the entire pumping periods. From the above two strategies it can concluded that global optimization is more advantageous as it considers the entire time period and therefore constraints are considered for the entire time horizon. Selection between both the strategies can be based on the criteria of economic or social considerations.
Global strategy solution was cross checked by running the solute transport model with the resulted optimum pumping/recharge rates. Comparison study was carried with and without the hydraulic gradient control wells on the redistribution of the contaminant. When there was no control of hydraulic gradient on the wells then the pumping effect was negligible and after about 4 year the plume started moving outside the model area. With the hydraulic gradient control wells, the plume contained in the original boundaries and helped in restoring the aquifer.
Discussion:
The paper was interesting as it gives us idea of how linear programming is applied in finding out the optimum location of the wells and their pumping/recharge rates for the contaminant removal with the hydraulic gradient control. The paper gave a good insight of the two solution strategies, their advantages and limitations. Comparative study of how the solutions differ for the study area when we consider these two solution strategies was very informative.
In the paper, during the beginning of the problem itself it is assumed that it has existing well network, therefore cost impact is not taken into consideration. It would be interesting to see how the solution is affected by the cost implications. Modeling the linear program corresponding to the cost also would give a more realistic optimized solution.
Dorothy Fisher Atwood, Steven M. Gorelick, Hydraulic Gradient Control for Ground Water Contaminant Removal, 1985, Journal of Hydrology
Summary:
The paper explains about how linear programming can be used in optimizing the well location and recharging/pumping schedules so as to minimize total pumping and recharge. The planning procedure comprises of two stages, first to simulate the ground water flow and solute transport model and study the removal of contaminant under the assumed velocity; secondly the analyze the model with the relevant constraints and objectives is fed into the linear program for finding out the optimized solution.
In view of the increase of groundwater pollution incidents, aquifer planning and restoring has become of great interest. The present paper illustrates the methodology of controlling the hydraulic gradient for removal of the contaminants from the groundwater. Initially one of the techniques used for groundwater management as considered by Molz and Bell (1977) was using embedding systems method, in which the constraints for the linear model included are groundwater flow equation, pumping rates and hydraulic gradients. But this technique was limited to using for small steady state flow problems. Further Remson and Gorelick (1980) applied embedded systems approach to identify the well location and rates to prevent the contaminant plume from migrating. Another technique in groundwater modeling is response matrix which is used in conjunction with linear and quadratic programming to find out the optimizing solution to maximize the well yields and minimizing the production cost.
The Rocky Mountain Arsenal near Denver, Colorado, U.S.A which was the military facility to manufacture and process toxic chemicals for military and industrial use. This area has a history of groundwater contamination because of the poor disposal techniques. For carrying out the study, model area (about 3 km2) considered is the north boundary of the Rocky Mountain Arsenal, as the flow in the unconfined aquifer is from south to north; therefore goal of the design is to prevent further migration of contaminant during the aquifer cleanup. The model area was discretized into 702 finite difference nodes approximating the boundaries. South west flux boundary was calculated by running the steady state simulation, constant north head boundary was based on the water levels, Western and eastern boundaries are represented as no-flow boundaries. The parameters of hydro-geologic considered in the study are derived from the groundwater and solute transport models.
The hydraulic gradient control design procedure comprises of two design stages. In stage I, simulation of solute transport is used to locate the shrinking plume boundary. For locating the plume boundary with respect to the potential gradient control wells, the contaminant transport is simulated through time and using an assumed velocity field. To reduce the contamination level to safe level the following factors play main role; number of wells, location and pumping rates of the contaminant removal wells. By trial and error most effective location of the well was selected which would restore the water quality of the groundwater more effectively. With the found well location study of plume boundary reduction over the years was carried out. It was found that with the selected well location the entire plume can be removed in over 12 years. This geometry of the plume if further considered for carrying out stage II.
In stage II, linear programming combined with ground water flow simulation is used to find out optimum well location and pumping/recharge rates are estimated which would minimize the migration of the plume by controlling the hydraulic gradient. Objective function of the problem would be minimizing the pumping and recharging rate of the well for the management period of 32 pumping periods, constraints would be the hydraulic gradient control which will have decision variables associated with pumping and recharging.
There are two different solution strategies considered in the study of the project area. Sequential strategy uses series of sequential optimization for each pumping period. On the other hand single global optimization uses for total 32 pumping periods. Though the pumping/recharge rates are comparable between the two strategies, well selection and schedules of pumping are different. It was observed that cumulative pumping/recharge rates of global optimization was about 10% better than sequential solution over the entire pumping periods. From the above two strategies it can concluded that global optimization is more advantageous as it considers the entire time period and therefore constraints are considered for the entire time horizon. Selection between both the strategies can be based on the criteria of economic or social considerations.
Global strategy solution was cross checked by running the solute transport model with the resulted optimum pumping/recharge rates. Comparison study was carried with and without the hydraulic gradient control wells on the redistribution of the contaminant. When there was no control of hydraulic gradient on the wells then the pumping effect was negligible and after about 4 year the plume started moving outside the model area. With the hydraulic gradient control wells, the plume contained in the original boundaries and helped in restoring the aquifer.
Discussion:
The paper was interesting as it gives us idea of how linear programming is applied in finding out the optimum location of the wells and their pumping/recharge rates for the contaminant removal with the hydraulic gradient control. The paper gave a good insight of the two solution strategies, their advantages and limitations. Comparative study of how the solutions differ for the study area when we consider these two solution strategies was very informative.
In the paper, during the beginning of the problem itself it is assumed that it has existing well network, therefore cost impact is not taken into consideration. It would be interesting to see how the solution is affected by the cost implications. Modeling the linear program corresponding to the cost also would give a more realistic optimized solution.
Monday, January 26, 2009
Assignment # 2 (Article - 2)
Article Reference:
J.A. Frizzone, R.D Coelho, D. Dourado-Neto, R. Soliani, June 1997, Linear Programming model to optimize the water resource use in irrigation projects – An application to the senator Nilo Coelho Project
Summary:
Objective of the paper is to develop a linear programming model using all the factors effecting and influencing the profit of the irrigation project. Linear programming model was considered to optimize the cropping patterns and the water requirements based on the constraints like – water availability, water-yield relationship, land constraints, production cost, and product price. Vital goal while planning an irrigation project is to explore how to combine the existing resources so as to maximize the profit and minimize the cost. Mathematical model quantifies the optimum solution using the scare resource and meeting the proposed goals.
Linear programming model was developed based on maximizing the net income subjected to restrictions of cropping area and water availability. Gross income was considered as proportional to the production and variable component is dependent on seasonal irrigation depth. Objective function was to maximize the net income which resulted in the following restrictions - seasonal water requirement of the crop should be less than or equal to the annual volume of available water, crop irrigated area should be less than the crop restricted area, total planted area restriction of each month and irrigated depth at any interval should not exceed the irrigated depth corresponding to maximum production. Considering all these constraints, objective and functions of the problem, linear programming model is used to optimize a solution for the cropping pattern in the region.
Case study: Model was applied to Senator “Nilo Coelho” irrigation project in Petrolina - Brazil
The aim of the model was to generate a optimal crop pattern suitable for the area and which maximizes the net income. The functions used in model area – water, seeding season, production cost (excluding the cost fo water) and product price. Crop water requirement was estimated based on the total irrigation depth in relation to the maximum Evapo-Transpiration of the crop. Monthly available water considered is Annual available water considered for the model is 66644500 (m3). Using these constraints and considering the crop area requirements, the linear programming model resulted in optimized crop planning. Though all the crops are irrigated with a deficit, recommended irrigation level of each crop satisfy the objective of maximizing the net income. Optimization model (LP) estimated net income of 53$ higher than the traditional crop pattern.
Sensitivity analysis was carried to see how the marginal cost, water availability, marginal net income and water misuse affects the optimum solution proposed. As the misuse of water will eventually effect the net income generated, It was recommended that when the resource is becoming scare, there should be a differential amount associated to the excess amount of water used by the users, this will improve the strategies involved in water management.
Discussions
Paper was interesting as it dealt with the basis of how the linear programming is carried out in planning a irrigation project. With the considered case study it gives a practical insight of how optimization modeling can be used in estimating an optimum crop pattern considering the maximum net income. The paper insights about various sensitivity analysis, which could be carried out to check the optimum solution, thereby looking into the problem in a broader approach.
If I was carrying out my research in the same field then my future work for this topic would be to analyze more on the sensitivity of water availability and the irrigation methods. How the net income be affected using different methods of irrigation would be interesting topic to explore.
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