Debele, B., Srinivasan, R., and Parlange, J. Y. (2008). "Coupling upland watershed and downstream waterbody hydrodynamic and water quality models (SWAT and CE-QUAL-W2) for better water resources management in complex river basins." Environmental Modeling and Assessment, 13(1), 135-153.
The article presents a modeling framework of water quantity and quality of upland watershed and a downstream reservoir. Two models have been coupled: SWAT (Soil & Water Assessment Tool) and CE-QUAL-W2. SWAT is a hydrological and hydraulic 1-D hydrodynamic and water quality model used to simulate upland watershed and narrower streams. CE-QUAL-W2 is a waterbody laterally averaged (2-D) hydrodynamic model, suited for narrow and deep waterbodies where lateral variation is minimum. This modeling approach has been tested in Cedar Creek watershed, Texas. The main land uses is agriculture, forest and urban areas. The watershed is drained by two main creeks (Cedar and Kings) and seven smaller tributaries which feed into the Cedar Creek Reservoir. The mean depth of the reservoir is 6.5 meters, a surface area of 34,300 acres and a volume of 566,000 acre-feet. About 25 % of total reservoir inflow is lost through evaporation and approximately 10 % is withdrawn for urban consumption (Fort Worth and nearby towns). Data from a period of 5 years, from 1997 to 2001, was used to calibrate the models. The calibration of the reservoir hydrodynamic showed good waterbalance match between the observed data and simulated results. The water quality calibration was performed with first temperature followed by Dissolved Oxygen. A second dataset of water quality parameters such as organic nitrogen, organic phosphorus, phosphate, chlorophyll a, total nitrogen, and total phosphorus concentration, were available and used in the calibration. Comparison among observed and simulated water quality parameters showed reasonable agreements. It was concluded that this framework can properly simulate seasonal and intraseasonal distributions of many water quality variables, with exception of Chl-a, TP, TN and NH3/NH4. The reasons for that could be by low quality of these input dataset and error propagation and compounding. In conclusion, the authors state that the integration of such models of spatially variable upland watershed hydrological and water quality models with downstream waterbody hydrodynamic and water quality models can help the water resources management, allowing the backtrack of the spatial sources of contaminants and support a good decision making for water quality standards in downstream waterbody.
segunda-feira, 21 de setembro de 2009
sexta-feira, 28 de agosto de 2009
Summer Summary
This post is a summary of the main ideas collected during the research period of summer. In total, I read completely 16 articles, and another number of incompletely readings. The research focused mainly in two topics: my present research, which is stormwater sustainability, and optimization techniques, mainly focused in multi-objective genetic algorithm.
For the first and more important topic of my research in this summer, the readings helped me to support the main ideas of the hydrologic footprint residence. HFR is a new metric used to assess the impacts of urbanization in the hydrologic flow regime. Many articles served as references to characterize the impact of urbanization in the hydrological regime. The transformation of natural land covers as forest and grassland to impervious covers alters most of the hydrological processes such as interception, evapotranspiration, infiltration and overland runoff.
In the revised literature, it was identified the main hydrologic metrics used to assess the impact of urbanization. Most of the metrics are based in time series of flow discharges. The main metrics found are: flow frequency curve, flow duration curve, TQmean, which is fraction of year that flow rate exceeds the mean flow rate of the entire flow time series, TQ0.5yr, which is the fraction of year that the flow rate exceeds the historical half-year peak flow rate, peak flow, storm flow duration, time-to-peak, ratio of time-to-peak to storm flow event duration, event-mean rise rate, event-mean fall rate, duration that the flow rate exceeds 75% of the peak flow rate in an event, ratio of event-peak-duration to total event duration, and IHA (indices of hydrological alteration). Those metrics can be used to evaluate different alternatives of development, Best Management Practices (BMPs) and Low Impact Development (LID).
Besides that, an interesting discussion about the effectiveness of BMPs was addressed in some articles. The argument is BMPs introduces a sustained flow for most of the storms which can harm downstream communities. BMPs are design to attenuate bigger storms. Besides that, urbanization increases the frequency of flow events. The combination of more frequent events with sustained flow is being questioned by recent researches.
Another topics explored during this research are the links between the hydrological flow regime and heath of instream ecosystems. Poff et al (1997) summarizes the knowledge about formation of habitats and the natural hydrological regime. Scientific community agrees that stream is a master variable for instream environments because it regulates most of biological and physicochemical processes in rivers. The natural variability of low and high flows plays a crucial role in the entire life cycle of instream and riverine species. Watershed management has been limited to water quality and one aspect of water quantity, which is minimum flow.
The second set of articles is related to optimization algorithms. Two interesting articles present a new heuristic optimization technique called Harmony Search (HS). HS is inspired the way musician improvise harmony searching for maximize the aesthetic estimation of music (objective function). The decision variables are the pitches (sounds) musicians play. Several problems are tested in the articles, and HS presented better performance when compared to other optimization techniques such as Generalized Reduced Gradient (GRC), Evolutionary Programming (EP), Genetic Algorithm (GA), and Nonlinear Programming Gradient (NLPG). This better efficiency, however, should be looked with attention, since performance of methods can be highly dependent of parameters and the problems itself.
The last group of articles is focused in Multi-objective optimization techniques, more specifically genetic algorithms. The objective here is to understand the main operators used in different techniques. Two methods have been studied in more details: MOGA and NSGA-II. One article combined the use of MOGA and Constrained Differential Dynamic Programming in a surface reservoir allocation problem.
In summary, important goals have been achieved during this summer period. The idea of reading two papers a week, one specific of my research and other more general, to discuss in the research group is really efficient. My reading and writing skills have improved a lot in period. I hope we can continue to do that with, hopefully, more students contributing to the discussion.
For the first and more important topic of my research in this summer, the readings helped me to support the main ideas of the hydrologic footprint residence. HFR is a new metric used to assess the impacts of urbanization in the hydrologic flow regime. Many articles served as references to characterize the impact of urbanization in the hydrological regime. The transformation of natural land covers as forest and grassland to impervious covers alters most of the hydrological processes such as interception, evapotranspiration, infiltration and overland runoff.
In the revised literature, it was identified the main hydrologic metrics used to assess the impact of urbanization. Most of the metrics are based in time series of flow discharges. The main metrics found are: flow frequency curve, flow duration curve, TQmean, which is fraction of year that flow rate exceeds the mean flow rate of the entire flow time series, TQ0.5yr, which is the fraction of year that the flow rate exceeds the historical half-year peak flow rate, peak flow, storm flow duration, time-to-peak, ratio of time-to-peak to storm flow event duration, event-mean rise rate, event-mean fall rate, duration that the flow rate exceeds 75% of the peak flow rate in an event, ratio of event-peak-duration to total event duration, and IHA (indices of hydrological alteration). Those metrics can be used to evaluate different alternatives of development, Best Management Practices (BMPs) and Low Impact Development (LID).
Besides that, an interesting discussion about the effectiveness of BMPs was addressed in some articles. The argument is BMPs introduces a sustained flow for most of the storms which can harm downstream communities. BMPs are design to attenuate bigger storms. Besides that, urbanization increases the frequency of flow events. The combination of more frequent events with sustained flow is being questioned by recent researches.
Another topics explored during this research are the links between the hydrological flow regime and heath of instream ecosystems. Poff et al (1997) summarizes the knowledge about formation of habitats and the natural hydrological regime. Scientific community agrees that stream is a master variable for instream environments because it regulates most of biological and physicochemical processes in rivers. The natural variability of low and high flows plays a crucial role in the entire life cycle of instream and riverine species. Watershed management has been limited to water quality and one aspect of water quantity, which is minimum flow.
The second set of articles is related to optimization algorithms. Two interesting articles present a new heuristic optimization technique called Harmony Search (HS). HS is inspired the way musician improvise harmony searching for maximize the aesthetic estimation of music (objective function). The decision variables are the pitches (sounds) musicians play. Several problems are tested in the articles, and HS presented better performance when compared to other optimization techniques such as Generalized Reduced Gradient (GRC), Evolutionary Programming (EP), Genetic Algorithm (GA), and Nonlinear Programming Gradient (NLPG). This better efficiency, however, should be looked with attention, since performance of methods can be highly dependent of parameters and the problems itself.
The last group of articles is focused in Multi-objective optimization techniques, more specifically genetic algorithms. The objective here is to understand the main operators used in different techniques. Two methods have been studied in more details: MOGA and NSGA-II. One article combined the use of MOGA and Constrained Differential Dynamic Programming in a surface reservoir allocation problem.
In summary, important goals have been achieved during this summer period. The idea of reading two papers a week, one specific of my research and other more general, to discuss in the research group is really efficient. My reading and writing skills have improved a lot in period. I hope we can continue to do that with, hopefully, more students contributing to the discussion.
End of Summer I - List of articles
The summer is over... here is the list of articles that I read in this period:
1. Bertrand-Krajewski, J.-L., Barraud, S., and Chocat, B. (2000). "Need for improved methodologies and measurements for sustainable management of urban water systems." Environmental Impact Assessment Review, 20(3), 323-331.
2. Deb, K., Pratap, A., Agarwal, S., and Meyarivan, T. (2002). "A fast and elitist multiobjective genetic algorithm: NSGA-II." Evolutionary Computation, IEEE Transactions on, 6(2), 182-197.
3. Derek B. Booth, James R. Karr, Sally Schauman, Christopher P. Konrad, Sarah A. Morley, Marit G. Larson, and Stephen J. Burges. (2004). "Reviving Urban Streams: Land Use, Hydrology, Biology, and Human Behavior." Journal of the American Water Resources Association, 40(5), 1351-1364.
4. Egderly, J. L., Roesner, L. A., Rohrer, C. A., and Gironas, J. A. "Quantifying Urban-Induced Flow Regime Alteration and Evaluating Mitigation Alternatives Using Mathematical Models and Hydrologic Metrics." 425.
5. Fan, C., and Li, J. (2004). "A Modelling Analysis of Urban Stormwater Flow Regimes and their Implication for Stream Erosion." Water Quality Research Journal of Canada, 39(4), 356-61.
6. Geem, Z. W. (2009). "Harmony search optimisation to the pump-included water distribution network design." Civil Engineering and Environmental Systems, 26(3), 211 - 221.
7. Getter, K. L., Rowe, D. B., and Andresen, J. A. (2007). "Quantifying the effect of slope on extensive green roof stormwater retention." Ecological Engineering, 31(4), 225-231.
8. Graham, P., Maclean, L., and Medina, D. (2004). "The Role of Water Balance Modelling in the Transition to Low Impact Development." Water Quality Research Journal of Canada, 39(4), 331-42.
9. Konak, A., Coit, D. W., and Smith, A. E. (2006). "Multi-objective optimization using genetic algorithms: A tutorial." Reliability Engineering & System Safety, 91(9), 992-1007.
10. McCuen, R. H. (1979). "Downstream Effects of Stormwater Management Basins." Journal of the Hydraulics Division, 105(11), 1343-1356.
11. Nehrke, S. M., and Roesner, L. A. (2004). "Effects of Design Practice for Flood Control and Best Management Practices on the Flow-Frequency Curve." Journal of Water Resources Planning and Management, 130(2), 131-139.
12. Poff, N. L., Allan, J. D., Bain, M. B., Karr, J. R., Prestegaard, K. L., Richter, B. D., Sparks, R. E., and Stromberg, J. C. (1997). "The Natural Flow Regime." BioScience, 47(11), 769-784.
13. Reddy, M., and Kumar, D. (2006). "Optimal Reservoir Operation Using Multi-Objective Evolutionary Algorithm." Water Resources Management, 20(6), 861-878.
14. Roesner, L. A., Bledsoe, B. P., and Brashear, R. W. (2001). "Are Best-Management-Practice Criteria Really Environmentally Friendly?" Journal of Water Resources Planning and Management, 127(3), 150-154.
15. Yang, C.-C., Chang, L.-C., Yeh, C.-H., and Chen, C.-S. (2007). "Multiobjective Planning of Surface Water Resources by Multiobjective Genetic Algorithm with Constrained Differential Dynamic Programming." Journal of Water Resources Planning and Management, 133(6), 499-508.
16. Zong Woo Geem, Joong Hoon Kim, and Loganathan, G. V. (2001). "A New Heuristic Optimization Algorithm: Harmony Search." SIMULATION, 76(2), 60-68.
1. Bertrand-Krajewski, J.-L., Barraud, S., and Chocat, B. (2000). "Need for improved methodologies and measurements for sustainable management of urban water systems." Environmental Impact Assessment Review, 20(3), 323-331.
2. Deb, K., Pratap, A., Agarwal, S., and Meyarivan, T. (2002). "A fast and elitist multiobjective genetic algorithm: NSGA-II." Evolutionary Computation, IEEE Transactions on, 6(2), 182-197.
3. Derek B. Booth, James R. Karr, Sally Schauman, Christopher P. Konrad, Sarah A. Morley, Marit G. Larson, and Stephen J. Burges. (2004). "Reviving Urban Streams: Land Use, Hydrology, Biology, and Human Behavior." Journal of the American Water Resources Association, 40(5), 1351-1364.
4. Egderly, J. L., Roesner, L. A., Rohrer, C. A., and Gironas, J. A. "Quantifying Urban-Induced Flow Regime Alteration and Evaluating Mitigation Alternatives Using Mathematical Models and Hydrologic Metrics." 425.
5. Fan, C., and Li, J. (2004). "A Modelling Analysis of Urban Stormwater Flow Regimes and their Implication for Stream Erosion." Water Quality Research Journal of Canada, 39(4), 356-61.
6. Geem, Z. W. (2009). "Harmony search optimisation to the pump-included water distribution network design." Civil Engineering and Environmental Systems, 26(3), 211 - 221.
7. Getter, K. L., Rowe, D. B., and Andresen, J. A. (2007). "Quantifying the effect of slope on extensive green roof stormwater retention." Ecological Engineering, 31(4), 225-231.
8. Graham, P., Maclean, L., and Medina, D. (2004). "The Role of Water Balance Modelling in the Transition to Low Impact Development." Water Quality Research Journal of Canada, 39(4), 331-42.
9. Konak, A., Coit, D. W., and Smith, A. E. (2006). "Multi-objective optimization using genetic algorithms: A tutorial." Reliability Engineering & System Safety, 91(9), 992-1007.
10. McCuen, R. H. (1979). "Downstream Effects of Stormwater Management Basins." Journal of the Hydraulics Division, 105(11), 1343-1356.
11. Nehrke, S. M., and Roesner, L. A. (2004). "Effects of Design Practice for Flood Control and Best Management Practices on the Flow-Frequency Curve." Journal of Water Resources Planning and Management, 130(2), 131-139.
12. Poff, N. L., Allan, J. D., Bain, M. B., Karr, J. R., Prestegaard, K. L., Richter, B. D., Sparks, R. E., and Stromberg, J. C. (1997). "The Natural Flow Regime." BioScience, 47(11), 769-784.
13. Reddy, M., and Kumar, D. (2006). "Optimal Reservoir Operation Using Multi-Objective Evolutionary Algorithm." Water Resources Management, 20(6), 861-878.
14. Roesner, L. A., Bledsoe, B. P., and Brashear, R. W. (2001). "Are Best-Management-Practice Criteria Really Environmentally Friendly?" Journal of Water Resources Planning and Management, 127(3), 150-154.
15. Yang, C.-C., Chang, L.-C., Yeh, C.-H., and Chen, C.-S. (2007). "Multiobjective Planning of Surface Water Resources by Multiobjective Genetic Algorithm with Constrained Differential Dynamic Programming." Journal of Water Resources Planning and Management, 133(6), 499-508.
16. Zong Woo Geem, Joong Hoon Kim, and Loganathan, G. V. (2001). "A New Heuristic Optimization Algorithm: Harmony Search." SIMULATION, 76(2), 60-68.
segunda-feira, 27 de julho de 2009
Harmony Search
Article Review
Geem, Z.W., Kim, J.H., Loganathan, G.V. (2001) “A New Heuristic Optimization Algorithm: Harmony Search”. 76(2): 60-68.
This paper presents the algorithm Harmony Search (HS), a new heuristic optimization algorithm inspired in the way musician improvise harmonies. The analogy with music is: musical performance seeks a harmony with maximum aesthetic estimation, as the optimization algorithm seeks the best solution. The aesthetic estimation represents the objective function and the pitches of instruments represent decision variables. The decision variables achieve better solution by a process of practice. After each iteration, the solution is evaluated. If the harmony is better than the previous ones, it is included in the Harmony Memory. The process is repeated until the stopping criteria is satisfied.
The harmony memory is initialized with random values. A new harmony is generated based on the solutions already present in the harmony search. If the new harmony is better than the ones in the harmony memory, it is included on it, and the worst harmony is excluded. In order to increase the decision space and find the global optimum, a parameter called Harmony Memory Considering Rate (HMCR), ranging from 0 to 1, is used to randomly generate new solutions. HMCR is uniformly generated. If it is above the current value of the HMCR, the algorithm selects a new variable with certain probability and introduces the new random value.
Another operator is used to escape local optima, similar to crossover in the genetic algorithm (GA). The Pitch Adjusting Rate (PAR) is used to select a variable with certain probability and shifts the value with its neighbors. The article uses the example of the solution {1,3,4,6,7,9}. The value {6} can be moved to neighboring {4} or {7}.
The article illustrates the harmony search with 3 problems found in the literature. The first one is the Traveling Salesman Problem (TSP), which tries to find the shortest path for a salesman that has to visit a certain number of cities once. The second problem is a 2 dimension constrained minimization problem. The performance of HS is compared with others methods like GA, Generalized Reduced Gradient (GRC) and Evolutionary Programming (EP). HS had better performance compared to the other methods. The last problem is the design of a pipeline network for water supply consisted of 32 nodes, 34 links and 3 loops. The results were compared with GA and Nonlinear Programming Gradient (NLPG). The HS produced the solution with the least cost related to the other methods.
Discussion
The HS algorithm is a very interesting methodology. Particularly for me that play the guitar, was very curious to see how real life phenomena can be invently used to develop new techniques to solve older and new problems. This paper was also interesting because I had the opportunity to attend the talk of one of the authors in the 2009 US-Korea Conference on Science, Technology and Entrepreneurship, last July 16-19, 2009 in Raleigh, North Carolina.
Geem, Z.W., Kim, J.H., Loganathan, G.V. (2001) “A New Heuristic Optimization Algorithm: Harmony Search”. 76(2): 60-68.
This paper presents the algorithm Harmony Search (HS), a new heuristic optimization algorithm inspired in the way musician improvise harmonies. The analogy with music is: musical performance seeks a harmony with maximum aesthetic estimation, as the optimization algorithm seeks the best solution. The aesthetic estimation represents the objective function and the pitches of instruments represent decision variables. The decision variables achieve better solution by a process of practice. After each iteration, the solution is evaluated. If the harmony is better than the previous ones, it is included in the Harmony Memory. The process is repeated until the stopping criteria is satisfied.
The harmony memory is initialized with random values. A new harmony is generated based on the solutions already present in the harmony search. If the new harmony is better than the ones in the harmony memory, it is included on it, and the worst harmony is excluded. In order to increase the decision space and find the global optimum, a parameter called Harmony Memory Considering Rate (HMCR), ranging from 0 to 1, is used to randomly generate new solutions. HMCR is uniformly generated. If it is above the current value of the HMCR, the algorithm selects a new variable with certain probability and introduces the new random value.
Another operator is used to escape local optima, similar to crossover in the genetic algorithm (GA). The Pitch Adjusting Rate (PAR) is used to select a variable with certain probability and shifts the value with its neighbors. The article uses the example of the solution {1,3,4,6,7,9}. The value {6} can be moved to neighboring {4} or {7}.
The article illustrates the harmony search with 3 problems found in the literature. The first one is the Traveling Salesman Problem (TSP), which tries to find the shortest path for a salesman that has to visit a certain number of cities once. The second problem is a 2 dimension constrained minimization problem. The performance of HS is compared with others methods like GA, Generalized Reduced Gradient (GRC) and Evolutionary Programming (EP). HS had better performance compared to the other methods. The last problem is the design of a pipeline network for water supply consisted of 32 nodes, 34 links and 3 loops. The results were compared with GA and Nonlinear Programming Gradient (NLPG). The HS produced the solution with the least cost related to the other methods.
Discussion
The HS algorithm is a very interesting methodology. Particularly for me that play the guitar, was very curious to see how real life phenomena can be invently used to develop new techniques to solve older and new problems. This paper was also interesting because I had the opportunity to attend the talk of one of the authors in the 2009 US-Korea Conference on Science, Technology and Entrepreneurship, last July 16-19, 2009 in Raleigh, North Carolina.
During our weekly discussion meeting, we tried to compared the differences and similarities between HS and GA. As a heuristic method, HS is similar to GA. One aspect that seems important is that HS creates a new solution based in all existing solutions presented in the harmony memory, while GA creates a new solution only with two previous solutions (parents).
sexta-feira, 26 de junho de 2009
Downstream Effects of Stormwater Management Basins
Article Review
McCuen, R.H. (1979) “Downstream effects of Stormwater Management Basins” Journal of the Hydraulics Division, Vol. 105, No. 11.
Prof. McCuen addresses the problem of hydrological alteration due urbanization. The use of impervious materials decreases natural storage, increasing peak rates, decreasing time-to-peak, and increasing the volumes of runoff and sediments. To mitigate these detrimental effects storm water management (SWM) is required. However, according to the paper, many SWM strategies fail in mitigate the urbanization effects because “they only attempt to limit peak flow rates and sediments volumes” to predevelopment conditions. This is in general attempted by the use of detention basins. This strategy, however, is not sufficient. This problem lead to main question of the article: “Are SWM basins effectively meeting the intent of stormwater management?”
“Urban development causes a decrease in natural storage, including infiltration, interception, and depression storage”. SWM basin is an attempt to restore the loss of natural storage in the watershed. This volume can be artificially restored, but the timing characteristics introduced by detention basins are significantly different from the predevelopment conditions. In natural conditions, the major part of the storage volume is filled during the storm event, while in a detention facility this storage is rapidly filled during the risen portion of the hydrograph.
A second effect introduced by detention basin is that the increased volume of direct runoff is released at a higher rate when compared to natural storage. This cause increase in the duration of bankfull flows.
Due the reasons explained so far, the work examines the hypothesis “that, when changes in both timing characteristics and flow volumes are not corrected by SWM, they may have an adverse effect on flow conditions downstream from the SWM basin.”
A 2.12 square mile watershed was simulated using the Soil Conservation Service TR-20 hydrological model. The predominant soils are silt loams, characterized as deep, well-drained, and moderately erodible. Simulations indicate that peak flow increases from 11.7 to 59.3 cfs (factor of five!!!) from pre-development to urbanized condition of one catchment for the 10 yr-storm. In terms of volume, there is an increase of 100%. The time-to-peak decrease 7 minutes. Introducing a detention basin, the peak flow is reduced to 13.08 cfs, but the time-to-peak is 36 minutes greater than that which existed prior to development. A compared analysis is done for the 100 yr-storm. The effects are the same, but the differences are much lower.
Looking further downstream in the watershed, the computation indicates that for the 100 yr-storm the SWM basin increases the peak flow compared to the post development with no control. This is true for approximately 5 miles downstream the storage facility. The reason for that is changes in timing characteristics affects the runoff conditions downstream.
After the hydrological analysis, the author has approached the bedload transport. Although its is recognized the difficulty in estimating bedload discharges, a theoretical model can be used to assess different scenarios and trace comparisons between them. A model developed by Goncharov was used to predict the sediment discharge as a function of mean flow velocity, mean sediment diameter, the critical velocity of sediment, and the mean depth. The previous discussed scenarios were evaluated to generate estimative of sediment yield. The results indicate that even with the SWM basin there is a significant increase in total volume of sediment. This is due the sustain flow introduced by the basin, which induce higher velocities than the critical velocity over a longer period.
The author finalizes the article with some considerations related with SWM policies and designs. He considers three aspects important:
(1) “The recognition of a comprehensive interpretation to the definition of the intent of SWM;
(2) A policy statement that reflects this interpretation and provides the guidelines that are required to institute proper design methods;
(3) Design methods and construction practices that are representative of the state-of-art and the fully consider hydrologic changes that go along with the urbanization process.”
He suggests that alternatives like grass-lined swales, rooftops detention, and porous pavements are SWM measures that better represents the natural storage found in predevelopment conditions, both in volume and temporal characteristics. A second alternative is to make change in the basin designs, although that may cause conflicts between flood control and pollution/sediment control, for example.
McCuen, R.H. (1979) “Downstream effects of Stormwater Management Basins” Journal of the Hydraulics Division, Vol. 105, No. 11.
Prof. McCuen addresses the problem of hydrological alteration due urbanization. The use of impervious materials decreases natural storage, increasing peak rates, decreasing time-to-peak, and increasing the volumes of runoff and sediments. To mitigate these detrimental effects storm water management (SWM) is required. However, according to the paper, many SWM strategies fail in mitigate the urbanization effects because “they only attempt to limit peak flow rates and sediments volumes” to predevelopment conditions. This is in general attempted by the use of detention basins. This strategy, however, is not sufficient. This problem lead to main question of the article: “Are SWM basins effectively meeting the intent of stormwater management?”
“Urban development causes a decrease in natural storage, including infiltration, interception, and depression storage”. SWM basin is an attempt to restore the loss of natural storage in the watershed. This volume can be artificially restored, but the timing characteristics introduced by detention basins are significantly different from the predevelopment conditions. In natural conditions, the major part of the storage volume is filled during the storm event, while in a detention facility this storage is rapidly filled during the risen portion of the hydrograph.
A second effect introduced by detention basin is that the increased volume of direct runoff is released at a higher rate when compared to natural storage. This cause increase in the duration of bankfull flows.
Due the reasons explained so far, the work examines the hypothesis “that, when changes in both timing characteristics and flow volumes are not corrected by SWM, they may have an adverse effect on flow conditions downstream from the SWM basin.”
A 2.12 square mile watershed was simulated using the Soil Conservation Service TR-20 hydrological model. The predominant soils are silt loams, characterized as deep, well-drained, and moderately erodible. Simulations indicate that peak flow increases from 11.7 to 59.3 cfs (factor of five!!!) from pre-development to urbanized condition of one catchment for the 10 yr-storm. In terms of volume, there is an increase of 100%. The time-to-peak decrease 7 minutes. Introducing a detention basin, the peak flow is reduced to 13.08 cfs, but the time-to-peak is 36 minutes greater than that which existed prior to development. A compared analysis is done for the 100 yr-storm. The effects are the same, but the differences are much lower.
Looking further downstream in the watershed, the computation indicates that for the 100 yr-storm the SWM basin increases the peak flow compared to the post development with no control. This is true for approximately 5 miles downstream the storage facility. The reason for that is changes in timing characteristics affects the runoff conditions downstream.
After the hydrological analysis, the author has approached the bedload transport. Although its is recognized the difficulty in estimating bedload discharges, a theoretical model can be used to assess different scenarios and trace comparisons between them. A model developed by Goncharov was used to predict the sediment discharge as a function of mean flow velocity, mean sediment diameter, the critical velocity of sediment, and the mean depth. The previous discussed scenarios were evaluated to generate estimative of sediment yield. The results indicate that even with the SWM basin there is a significant increase in total volume of sediment. This is due the sustain flow introduced by the basin, which induce higher velocities than the critical velocity over a longer period.
The author finalizes the article with some considerations related with SWM policies and designs. He considers three aspects important:
(1) “The recognition of a comprehensive interpretation to the definition of the intent of SWM;
(2) A policy statement that reflects this interpretation and provides the guidelines that are required to institute proper design methods;
(3) Design methods and construction practices that are representative of the state-of-art and the fully consider hydrologic changes that go along with the urbanization process.”
He suggests that alternatives like grass-lined swales, rooftops detention, and porous pavements are SWM measures that better represents the natural storage found in predevelopment conditions, both in volume and temporal characteristics. A second alternative is to make change in the basin designs, although that may cause conflicts between flood control and pollution/sediment control, for example.
quinta-feira, 25 de junho de 2009
Flow duration curves
Article Review
Fan, C., Li, James (2004) “A Modelling Analysis of Urban Stormwater Flow Regimes and their Implication for Stream Erosion” Water Quality Re. Journal Canada, Vol. 39, No. 4.
The objective of this paper is to analyze flow-duration characteristics of a stream, with and without control measures applied during and after urbanization and its potential for erosion.
“Flow duration curve is the complement of the cumulative distribution function of stream flow. It represents the relationship between the magnitude and frequency of daily, weekly, monthly or even longer period of time of stream flow for a particular watershed.” The flow duration curve is the relationship between exccedance probability and discharge.
According to the authors, stream erosion is a continuous process of removal and deposition of sediments. Urbanization can alters drastically this balance due alteration of the flow regime. Since measuring both discharge of solid and liquid is something difficult to perform, especially in the planning process of development, the hypothesis of this work is that hydrological models can be used to estimate the flow regimes alteration by the flow-duration curve and evaluate the implication on stream erosion.
A period of 3 months of measure data were used to calibrate the model ISWMS (Integrated Storm Water Management Simulator). The watershed was discretized in 9 sub catchments. The calibrated parameters were base flow and horton’s equation for infiltration. Twenty-seven years of hourly rainfall data was used in the long-term simulations.
Different degrees of development were tested by changing the percent of imperviousness (20, 30 and 40 %), of all catchment, with exception of catchment #5 which represents a wetland area. It was noted that urbanized duration curves are shifted from the original curve as more imperviousness is used, indicating that for the same discharge, the frequency is higher.
To analyze the impact of flow control measures, three scenarios were tested: (1) an extended detention basin was added to each subcatchment except subcatchment 5 (the wetland); (2) two extended detention basins were added, one more upstream and other downstream; and (3) an extended detention basin was added downstream of all the subcatchments. The basins were sized considering the criteria of capturing 5 mm of rainfall and the outlet orifices were sized for 24 and 48 hours.
The first analysis compared the use of detention basin in the outlet of the watershed (scenario 3). The results indicate that both 24 hrs and 48 hrs extended basins control the runoff greater than 0.1 m³/s. For lower flow than 0.05 m³/s, 24 hrs basins performed slightly better than 48 hrs basins, and the opposite for flows varying from 0.1 to 0.05 m³/s.
When other locations are analyzed, it was found that regional control (scenario 2) provide better control performance than scenario 3 for flows greater than 0.07 m³/s. Local control (scenario 1) generally performs best when the flow is less than 0.09 m³/s. The authors conclude that the optimal location of detention basis is dependent on the flow regime.
In summary, the paper concludes that urbanization can change significantly the hydrological regime of a watershed and that extended detention basins with 48 hours of detention time provide better control of flow-duration characteristics than 24 hours of detention for higher flows. For lower flows, the 24 hour basin perform better. This make the authors suggest that the detention basins should be sized based on the range of flows which determine the stability of a stream. Finally, the paper states that if a watershed is urbanized beyond 40 % of imperviousness, it may be impossible to restore the flow-duration curve to its original position.
Discussion
This paper seems valid in order to illustrate the impact of urbanization in the flow regime. It has used as a tool of analysis the flow duration curve, analyses that can be found in more literature (see last post). Some comments however I would like to do:
(1) The paper doesn’t specify the area of the watershed that is been analyzed. The findings of the work may not be extrapolate to other watershed with different scales;
(2) The period of calibration is very small (just 3 months). A period of verification of the modeling was not performed;
(3) The limit of 40 % of imperviousness indicating that it may be impossible to restore the flow-duration curve seems very specific for this particular watershed. Different hydrological characteristics may turn this number lower or even higher;
(4) The results shown in the work prove good control over the high flow portion of the flow duration curve. For lower flows (and high frequent event) none of the scenarios seems to replicate the predevelopment conditions (see last post);
(5) The original hypothesis of the work was partially proved. The hydrological alterations were demonstrated, but no further analysis was done to evaluate the implication of the alterations on stream erosion.
Fan, C., Li, James (2004) “A Modelling Analysis of Urban Stormwater Flow Regimes and their Implication for Stream Erosion” Water Quality Re. Journal Canada, Vol. 39, No. 4.
The objective of this paper is to analyze flow-duration characteristics of a stream, with and without control measures applied during and after urbanization and its potential for erosion.
“Flow duration curve is the complement of the cumulative distribution function of stream flow. It represents the relationship between the magnitude and frequency of daily, weekly, monthly or even longer period of time of stream flow for a particular watershed.” The flow duration curve is the relationship between exccedance probability and discharge.
According to the authors, stream erosion is a continuous process of removal and deposition of sediments. Urbanization can alters drastically this balance due alteration of the flow regime. Since measuring both discharge of solid and liquid is something difficult to perform, especially in the planning process of development, the hypothesis of this work is that hydrological models can be used to estimate the flow regimes alteration by the flow-duration curve and evaluate the implication on stream erosion.
A period of 3 months of measure data were used to calibrate the model ISWMS (Integrated Storm Water Management Simulator). The watershed was discretized in 9 sub catchments. The calibrated parameters were base flow and horton’s equation for infiltration. Twenty-seven years of hourly rainfall data was used in the long-term simulations.
Different degrees of development were tested by changing the percent of imperviousness (20, 30 and 40 %), of all catchment, with exception of catchment #5 which represents a wetland area. It was noted that urbanized duration curves are shifted from the original curve as more imperviousness is used, indicating that for the same discharge, the frequency is higher.
To analyze the impact of flow control measures, three scenarios were tested: (1) an extended detention basin was added to each subcatchment except subcatchment 5 (the wetland); (2) two extended detention basins were added, one more upstream and other downstream; and (3) an extended detention basin was added downstream of all the subcatchments. The basins were sized considering the criteria of capturing 5 mm of rainfall and the outlet orifices were sized for 24 and 48 hours.
The first analysis compared the use of detention basin in the outlet of the watershed (scenario 3). The results indicate that both 24 hrs and 48 hrs extended basins control the runoff greater than 0.1 m³/s. For lower flow than 0.05 m³/s, 24 hrs basins performed slightly better than 48 hrs basins, and the opposite for flows varying from 0.1 to 0.05 m³/s.
When other locations are analyzed, it was found that regional control (scenario 2) provide better control performance than scenario 3 for flows greater than 0.07 m³/s. Local control (scenario 1) generally performs best when the flow is less than 0.09 m³/s. The authors conclude that the optimal location of detention basis is dependent on the flow regime.
In summary, the paper concludes that urbanization can change significantly the hydrological regime of a watershed and that extended detention basins with 48 hours of detention time provide better control of flow-duration characteristics than 24 hours of detention for higher flows. For lower flows, the 24 hour basin perform better. This make the authors suggest that the detention basins should be sized based on the range of flows which determine the stability of a stream. Finally, the paper states that if a watershed is urbanized beyond 40 % of imperviousness, it may be impossible to restore the flow-duration curve to its original position.
Discussion
This paper seems valid in order to illustrate the impact of urbanization in the flow regime. It has used as a tool of analysis the flow duration curve, analyses that can be found in more literature (see last post). Some comments however I would like to do:
(1) The paper doesn’t specify the area of the watershed that is been analyzed. The findings of the work may not be extrapolate to other watershed with different scales;
(2) The period of calibration is very small (just 3 months). A period of verification of the modeling was not performed;
(3) The limit of 40 % of imperviousness indicating that it may be impossible to restore the flow-duration curve seems very specific for this particular watershed. Different hydrological characteristics may turn this number lower or even higher;
(4) The results shown in the work prove good control over the high flow portion of the flow duration curve. For lower flows (and high frequent event) none of the scenarios seems to replicate the predevelopment conditions (see last post);
(5) The original hypothesis of the work was partially proved. The hydrological alterations were demonstrated, but no further analysis was done to evaluate the implication of the alterations on stream erosion.
quinta-feira, 11 de junho de 2009
Are Best-Management-Practice really environmentally friendly?
Article Review
Roesner, L.A., Bledsoe, B.P., Brashear, R.W. (2001) “Are Best-Management-Practice really environmentally friendly?” Journal of Water Resources Planning and Management, v. 127, no. 3 (May/June).
This article examines the argument that best-management-pratice (BMP) doesn’t not protect urban streams properly. The definition of BMP is strategies to control of urban runoff, usually store structures as detention basins. The authors defend that the BMP is not the problem in itself, but rather the design guidance for BMP outlet flow control that doesn’t take into account the geomorphologic characteristics of the receiver stream.
The authors present a description of the impacts of urbanization in the hydrology of urban watershed. Some numbers illustrate the changes: the peak flow can increase by 2 to more than 10 in terms of magnitude. Also frequency of two-year peak runoff rate in the predevelopment state occurs three to eight times per year after urbanization. The effects of this changes cause severe stream channel erosion and downstream flooding. In terms of water quality, the effects of urban runoff also harm aquatic habitats.
Considering the increase of runoff, many municipalities require big storms to be controlled, in order that the post-development peak flow does not exceed the pre-development discharge. Common recurrence times are 10 and 25 years. Few locals control the 2-year storm. The article states that while detention basins reduce flooding, they are not effective in reducing erosion. One reason is due the sustained flow that detention ponds induce downstream. The outlet flow is prolonged, subjecting the stream channel for a longer period of time. The second reason is the basin only attenuates the flow of the design storm. Attenuation of different storms is coincidental. Considering that urbanization increases the frequency of pre-development peakflow and basins are designed to regulate storms higher than the 10 or 25 year-storms, most storms will pass through the structure unregulated, subjecting the downstream channel to erosive velocities more frequently.
For correcting the problem, the writers believe that “integrating the design of storage and outlet controls for flood control and BMPs it is possible to better control wet weather discharges to receiving waters over the entire range of flows that the facility experiences.” The question that stormwater managers should ask is: “given the potential flow of sediment and water out of the watershed, what are our options for achieving desired social and biological endpoints?”
The article proposes a two step approach to link biological indices to watershed parameters. The first step is to develop a relationship between stream geomorphologic characteristics and biologic indicators. The second step is to develop a relationship between watershed hydrogeometric parameters and stream geomorphologic parameters. It is believed that with this approach is possible to design holistic runoff control facilities into urban development so both flood protection and maintenance of ecosystem can be achieved.
Roesner, L.A., Bledsoe, B.P., Brashear, R.W. (2001) “Are Best-Management-Practice really environmentally friendly?” Journal of Water Resources Planning and Management, v. 127, no. 3 (May/June).
This article examines the argument that best-management-pratice (BMP) doesn’t not protect urban streams properly. The definition of BMP is strategies to control of urban runoff, usually store structures as detention basins. The authors defend that the BMP is not the problem in itself, but rather the design guidance for BMP outlet flow control that doesn’t take into account the geomorphologic characteristics of the receiver stream.
The authors present a description of the impacts of urbanization in the hydrology of urban watershed. Some numbers illustrate the changes: the peak flow can increase by 2 to more than 10 in terms of magnitude. Also frequency of two-year peak runoff rate in the predevelopment state occurs three to eight times per year after urbanization. The effects of this changes cause severe stream channel erosion and downstream flooding. In terms of water quality, the effects of urban runoff also harm aquatic habitats.
Considering the increase of runoff, many municipalities require big storms to be controlled, in order that the post-development peak flow does not exceed the pre-development discharge. Common recurrence times are 10 and 25 years. Few locals control the 2-year storm. The article states that while detention basins reduce flooding, they are not effective in reducing erosion. One reason is due the sustained flow that detention ponds induce downstream. The outlet flow is prolonged, subjecting the stream channel for a longer period of time. The second reason is the basin only attenuates the flow of the design storm. Attenuation of different storms is coincidental. Considering that urbanization increases the frequency of pre-development peakflow and basins are designed to regulate storms higher than the 10 or 25 year-storms, most storms will pass through the structure unregulated, subjecting the downstream channel to erosive velocities more frequently.
For correcting the problem, the writers believe that “integrating the design of storage and outlet controls for flood control and BMPs it is possible to better control wet weather discharges to receiving waters over the entire range of flows that the facility experiences.” The question that stormwater managers should ask is: “given the potential flow of sediment and water out of the watershed, what are our options for achieving desired social and biological endpoints?”
The article proposes a two step approach to link biological indices to watershed parameters. The first step is to develop a relationship between stream geomorphologic characteristics and biologic indicators. The second step is to develop a relationship between watershed hydrogeometric parameters and stream geomorphologic parameters. It is believed that with this approach is possible to design holistic runoff control facilities into urban development so both flood protection and maintenance of ecosystem can be achieved.
sexta-feira, 8 de maio de 2009
Blog 10 - Generating Alternatives
Article Review
Pan TC, Kao JJ (2009) GA-QP Model to Optimize Sewer System Design, JOURNAL OF ENVIRONMENTAL ENGINEERING, 135(1) 17-24
Pan and Kao implemented a Genetic-Algorithm (GA) and Quadratic Programming (QP) to generate alternative to the problem of designing sanitary sewer systems. This approach is proposed in order to reduce excessive computational effort presented by other optimization techniques. An alternative method is discrete differential dynamic programming (DDDP). DDDP, however, restricts the search space decreasing the chances of locating global optimum. Also, DDDP must be manually implemented, difficult to generalize to different systems. Another approach would be a GA-LP (linear programming) model, but linearization of nonlinear functions is complex.
The nice contribution of this work is the recognition that some important design factors and unquantifiable issues (public preference, for example) are not included within the optimization model. So, “the solution obtained from existing sewer design models may not be the best one or even feasible when unmodeled factors or issues are simultaneously evaluated”. Therefore, a model to generate alternatives (MGA) has been developed to evaluate the differences among the designs generated by the GA-QP and DDDP models.
Discussion
This article presents a nice application of generating alternatives, proposed in the previous article by Brill. Specifically to the design of the sewer system, the decision variables considered were slopes and buried depths. However, in real projects, there are a lot of “more important” aspects that may be subject to change by the decision-makers. For example, the network topology. Also, geology is a very important aspect in economic viability.
Pan TC, Kao JJ (2009) GA-QP Model to Optimize Sewer System Design, JOURNAL OF ENVIRONMENTAL ENGINEERING, 135(1) 17-24
Pan and Kao implemented a Genetic-Algorithm (GA) and Quadratic Programming (QP) to generate alternative to the problem of designing sanitary sewer systems. This approach is proposed in order to reduce excessive computational effort presented by other optimization techniques. An alternative method is discrete differential dynamic programming (DDDP). DDDP, however, restricts the search space decreasing the chances of locating global optimum. Also, DDDP must be manually implemented, difficult to generalize to different systems. Another approach would be a GA-LP (linear programming) model, but linearization of nonlinear functions is complex.
The nice contribution of this work is the recognition that some important design factors and unquantifiable issues (public preference, for example) are not included within the optimization model. So, “the solution obtained from existing sewer design models may not be the best one or even feasible when unmodeled factors or issues are simultaneously evaluated”. Therefore, a model to generate alternatives (MGA) has been developed to evaluate the differences among the designs generated by the GA-QP and DDDP models.
Discussion
This article presents a nice application of generating alternatives, proposed in the previous article by Brill. Specifically to the design of the sewer system, the decision variables considered were slopes and buried depths. However, in real projects, there are a lot of “more important” aspects that may be subject to change by the decision-makers. For example, the network topology. Also, geology is a very important aspect in economic viability.
quarta-feira, 29 de abril de 2009
Assignment # 10 - Alternatives
Article Review
BRILL ED (1979) USE OF OPTIMIZATION MODELS IN PUBLIC-SECTOR PLANNING, MANAGEMENT SCIENCE, 25.
According to the article, traditional optimization and multiobjective models fail in obtaining the best solution for public-sector planning. The limitations of using optimization models are failure in considering equity and difficulties in estimating benefits and costs. The author states that even a multiobjective approach, which should capture different perspectives of a problem, has practical limitations. In many problems, indifference curves are likely to reflect local optima. In a public planning problem, there might be issues not considered, which once introduced in the mathematical framework, likely bring the optimal to the inferior region of the original problem.
The article question which uses should optimization model be designed? There are set of problems that are inherently political in essence, which increase the complexity. In the second post I have addressed the article of Liebman (1978), which focus on “wicked” problems. Based on that, the authors argue that models should be used in a different way it has been used so far (1979).
The main idea the articles brings is that new types of optimization tools should be designed specifically to generate alternative plans and alternatives. To better understand the problem and generate alternatives is important creativity and inventiveness. Ways of using optimization models in a planning process are discussed in more detail in the article, like the use of optimization and simulation models. For this article, simulation model means examining a specific design in details. The optimization model identifies preliminary alternatives and the simulation model examines the solutions in more details. Use of analytical model and optimization models are also cited. The authors emphasize that there are a lot of gains in understanding the problem and feasible space in using a tool box of models.
The article comes up with the question: “optimization models should be capable of generating alternative solutions that: (1) meet minimal requirements, and (2) are different”? The question related to minimal requirements depends on the formulation of objective function and constraints. The issue of how different the solutions are is more difficult. A random sampling approach is suggested as an alternative method.
Discussion
The article brilliantly addresses how optimization problems should be used in order to effectively help the decision making process in the field of public planning. In real life, there will always be factors that cannot be incorporated in the optimization model, so generating multiple alternatives to be evaluated by decision-makers is a good idea. Some question, however, still remains: Brill says that a good set of alternatives should meet minimal requirements and be different. But how evaluate how different solutions are? He proposes an optimization approach to maximize the differences among solutions, but still this approach doesn’t contain all the aspects related to the decision-making process. I mean that two good solutions may be very similar in terms of modeling, but may contain completely different weights when evaluated by society. Or, two solutions may be different by the modeling, but for the decision-making process the solutions may be similar when intangible and incommensurable criteria are used.
BRILL ED (1979) USE OF OPTIMIZATION MODELS IN PUBLIC-SECTOR PLANNING, MANAGEMENT SCIENCE, 25.
According to the article, traditional optimization and multiobjective models fail in obtaining the best solution for public-sector planning. The limitations of using optimization models are failure in considering equity and difficulties in estimating benefits and costs. The author states that even a multiobjective approach, which should capture different perspectives of a problem, has practical limitations. In many problems, indifference curves are likely to reflect local optima. In a public planning problem, there might be issues not considered, which once introduced in the mathematical framework, likely bring the optimal to the inferior region of the original problem.
The article question which uses should optimization model be designed? There are set of problems that are inherently political in essence, which increase the complexity. In the second post I have addressed the article of Liebman (1978), which focus on “wicked” problems. Based on that, the authors argue that models should be used in a different way it has been used so far (1979).
The main idea the articles brings is that new types of optimization tools should be designed specifically to generate alternative plans and alternatives. To better understand the problem and generate alternatives is important creativity and inventiveness. Ways of using optimization models in a planning process are discussed in more detail in the article, like the use of optimization and simulation models. For this article, simulation model means examining a specific design in details. The optimization model identifies preliminary alternatives and the simulation model examines the solutions in more details. Use of analytical model and optimization models are also cited. The authors emphasize that there are a lot of gains in understanding the problem and feasible space in using a tool box of models.
The article comes up with the question: “optimization models should be capable of generating alternative solutions that: (1) meet minimal requirements, and (2) are different”? The question related to minimal requirements depends on the formulation of objective function and constraints. The issue of how different the solutions are is more difficult. A random sampling approach is suggested as an alternative method.
Discussion
The article brilliantly addresses how optimization problems should be used in order to effectively help the decision making process in the field of public planning. In real life, there will always be factors that cannot be incorporated in the optimization model, so generating multiple alternatives to be evaluated by decision-makers is a good idea. Some question, however, still remains: Brill says that a good set of alternatives should meet minimal requirements and be different. But how evaluate how different solutions are? He proposes an optimization approach to maximize the differences among solutions, but still this approach doesn’t contain all the aspects related to the decision-making process. I mean that two good solutions may be very similar in terms of modeling, but may contain completely different weights when evaluated by society. Or, two solutions may be different by the modeling, but for the decision-making process the solutions may be similar when intangible and incommensurable criteria are used.
segunda-feira, 13 de abril de 2009
Assignment # 9 - Multiobjective optmization
Shiau JT, Wu FC (2006) Compromise programming methodology for determining instream flow under multiobjective water allocation criteria, JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, 42(5), pp. 1179-1191.
Instream flow is one of the most challenging issues in water resources systems. Using a multiobjective optimization criterion, this study implements a framework to allocate water for three different uses: agriculture, urban and instream flow. The methodology considered three objectives: overall degree of hydrological alteration, shortage ratio for agriculture withdrawals, and shortage ratio for municipal uses. The degree of hydrological alteration was assessed using the Range of Variability Approach (RVA), which use 32 indicators of hydrological alteration (IHA) to evaluate hydrological impacts. The decision variable is instream flow release, considered to be constant during time.
The methodology was applied in Kaoping watershed in southern Taiwan. A weir operation diverts a maximum of 35 m³/s for municipal uses but more than that is also diverted to irrigation districts.
Results indicate that actual 9.5 m³/s instream flow is not enough to restore the natural flows variability. Weighting the three objective functions equally, optimal instream flow discharge of 26 m³/s could reduce hydrological alterations from a high to moderate state. A discharge of 93 m³/s would bring the hydrological regime to a low alteration state.
Discussion
This paper presents a very important study for water resources management. It combines shortage ratios and hydrological alteration statistics to perform a multiobjective optimization. The degree of hydrological alteration considered a kind of average value of the 32 IHA to represent the overall alteration. Future improvements could consider each of 32 indicators or the five groups of IHA. Considering variable instream flow releases would also be a interesting application.
quarta-feira, 1 de abril de 2009
Assignment # 8
Article Review
Neelakantan and Pundarikanthan address the problem of optimization for reservoir operation. Theoretically the modeling framework is well known. However, this simulation can be very time consuming. This article focuses on “developing a planning model for reservoir operation that uses a simulation-optimization approach”. The study implemented a backpropagation neural network to approximate the simulation model developed. This methodology was applied for an urban water distribution reservoir in Chennai, India. The particular study case seems to be very relevant since it has a high demand and serious hydrologic conditions which makes shortfalls frequent.
The article presented an interesting application of neural network in water resources systems. The study case seems to be relevant and highly representative of others systems in developing countries. The conclusion that addition of two reservoirs doesn’t improve the overall performance of the system seems in a first view very surprising. This conclusion is more relevant for developing countries that face difficult financial conditions.
Neelakantan TR, Pundarikanthan NV (2000) “Neural network-based simulation-optimization model for reservoir operation,” JOURNAL OF WATER RESOURCES PLANNING AND MANAGEMENT, 126(2) pp. 57-64
Neelakantan and Pundarikanthan address the problem of optimization for reservoir operation. Theoretically the modeling framework is well known. However, this simulation can be very time consuming. This article focuses on “developing a planning model for reservoir operation that uses a simulation-optimization approach”. The study implemented a backpropagation neural network to approximate the simulation model developed. This methodology was applied for an urban water distribution reservoir in Chennai, India. The particular study case seems to be very relevant since it has a high demand and serious hydrologic conditions which makes shortfalls frequent.
The entire framework comprises four stages. The first stage is the training of a backpropagation neural network, which is used to simulate reservoir operation. The second stage links the neural network model as a submodel with Hooke and Jeeves nonlinear optimization programming model, in order to identify operation policies. In the third stage, good operation policies are selected to be refined using the conventional simulation-optimization model.
Two scenarios were studied. Scenario 1 considered the existing reservoirs and the optimal operation was compared with the standard operation policy. Two proposed reservoirs were considered in Scenario 2. With respect of overall deficit index, the addition of proposed reservoirs don’t improve the system performance, although it reduces losses due spills.
Discussion
The article presented an interesting application of neural network in water resources systems. The study case seems to be relevant and highly representative of others systems in developing countries. The conclusion that addition of two reservoirs doesn’t improve the overall performance of the system seems in a first view very surprising. This conclusion is more relevant for developing countries that face difficult financial conditions.
quarta-feira, 18 de março de 2009
Assignment # 7
Article Review
Perez-Pedini C, Limbrunner JF, Vogel RM (2005) “Optimal location of infiltration-based best management practices for storm water management,” JOURNAL OF WATER RESOURCES PLANNING AND MANAGEMENT, 131(6) pp. 441-448
Under the perspective of storm water management and planning, the article presents a very useful tool. However, some issues related to the methodology seems unclear to me. The first one is related to how the infiltration BMP was modeled. Reduction of CN in five units could also be achieved by other kinds of measurements, like land use change, for example. Besides that, there are different kinds of infiltration BMPS (infiltration basins, trenches, pervious pavements etc) with different characteristics, efficiencies and costs. The article doesn’t address these issues properly in my opinion.
Perez-Pedini C, Limbrunner JF, Vogel RM (2005) “Optimal location of infiltration-based best management practices for storm water management,” JOURNAL OF WATER RESOURCES PLANNING AND MANAGEMENT, 131(6) pp. 441-448
The article presents a very interesting application of optimization techniques to study location of BMPs and its impacts of storm water management. A genetic algorithm was used to determine the optimal location of infiltration-based BMP’s. A distributed hydrologic model was used to simulate a 6400 ha watershed. The components of hydrological cycle considered in the simulation were precipitation, runoff, infiltration and groundwater flow. The rainfall-runoff separation method was the SCS-Curve Number. The BMP was introduced in the model by a binary integer decision variable that decreases the CN of a hydrological response unit (HFR) in five units.
Discussion
Under the perspective of storm water management and planning, the article presents a very useful tool. However, some issues related to the methodology seems unclear to me. The first one is related to how the infiltration BMP was modeled. Reduction of CN in five units could also be achieved by other kinds of measurements, like land use change, for example. Besides that, there are different kinds of infiltration BMPS (infiltration basins, trenches, pervious pavements etc) with different characteristics, efficiencies and costs. The article doesn’t address these issues properly in my opinion.
domingo, 1 de março de 2009
Assignment # 6 - Optimization of storm-water detention ponds system
Article Review
The objective function minimizes the total costs of implementation and operation of the ponds. These costs are: land-use values, construction, operation, maintenance and repair. Costs of conveying storm-water from the pond to the collector are not included. The decision variables are: active storage volume (mm), controlled release rate from the pond (mm/hour) and pond depth (m). “The goal is to obtain the least total cost associated with the detention ponds in all catchments, while satisfying the desired levels of overall system performances in terms of runoff quantity and quality control.” (Behera et al. 1999).
Behera, P, Papa, F., Adams, B (1999) “Optimization of Regional Storm-Water Management Systems” Journal of Water Resources Planning and Management, 125(2) pp. 107-114.
The present article proposes an optimization framework for detention ponds design parameters (storage, release rate and depth). First is developed a framework for a single detention pond. The methodology is expanded to consider a multiple parallel catchment system with one detention pond per catchment. The detention pond is simulated for quantity and quality constrains. The model considers total cost of implementing storm-water ponds for all of the catchments and provides a solution considering system-wide constraints instead of uniform control in all catchments.
The present article proposes an optimization framework for detention ponds design parameters (storage, release rate and depth). First is developed a framework for a single detention pond. The methodology is expanded to consider a multiple parallel catchment system with one detention pond per catchment. The detention pond is simulated for quantity and quality constrains. The model considers total cost of implementing storm-water ponds for all of the catchments and provides a solution considering system-wide constraints instead of uniform control in all catchments.
The objective function minimizes the total costs of implementation and operation of the ponds. These costs are: land-use values, construction, operation, maintenance and repair. Costs of conveying storm-water from the pond to the collector are not included. The decision variables are: active storage volume (mm), controlled release rate from the pond (mm/hour) and pond depth (m). “The goal is to obtain the least total cost associated with the detention ponds in all catchments, while satisfying the desired levels of overall system performances in terms of runoff quantity and quality control.” (Behera et al. 1999).
The quantity constraint is modeled by a simplified formulation that gives the average annual fraction of runoff quantity control. This model has the following parameters: runoff coefficient, rainfall event duration, rainfall event volume, and inter-event time. For different combination of storage volume and release rates, isoquant expressions for average annual fraction of runoff are developed. The quality model is defined as the average annual fraction of suspended solids removed.
The chosen optimization type is dynamic programming (DP), which “transforms the multiple catchment problem into a series of individual catchment problems (stages), then combines the solutions of the smaller problems to obtain the solution or policy of the overall (multiple catchment) problem” (Behera et al. 1999).
The formulation was implemented in a simple example case of three catchments. The overall constraints are achieve 50 % pollution control and 90 % runoff control at the discharge point. The objective function for these control values is: $ 754,072, while if this control values are considered for each catchment the cost would be $ 850,793 (13 % higher).
Discussion
This is one application of optimization techniques that interest me a lot. My course project in CVEN 665 is a detention ponds optimization framework, but we are considering just wet detention ponds as improve urban water quality. Behera et al. have analyzed both quality and quantity issues. The proposed framework is very relevant since it can help developers and municipalities to better plan their storm-water control systems.
Some issues are unclear to me. The runoff modeling is not explained in details. For example, we know that annual average values may not capture in details the runoff and quality control processes. Other meteorological variables, as evaporation are not considered. Usually is not a substantial for small detention ponds, but can be relevant for large storages. Besides that, the framework considers just suspended solids removal.
Future applications could analyze nutrients removal (nitrogen and phosphorus for example).
This specific formulation was implemented in computer spreadsheet. Future larger applications may be difficult to implement in this kind of computer environment.
segunda-feira, 23 de fevereiro de 2009
Assignment # 5 - Sensor Placement
Article Review
Berry, J., Fleisher, L, Hart, W. Phillips, C. and Watson, J.-P. (2005) “Sensor Placement in Municipal Water Networks”, Journal of Water Resources Planning and Management, 131(3) pp. 237-243
This article addresses the issue contaminant events in water distribution systems. The motivation is higher vulnerabilities in water networks due its distributed geography. An approach for determining an optimal sensor configuration in water distribution systems is presented. The optimization method minimizes the expected fraction of population exposed to a contaminant event. Integer programming techniques was used. Four assumptions were used:
1) An attack occurs at a single point in the network
2) Total population exposed
3) Sensors protect downstream populations
4) Transitions between periods are ignored
Three data sets were evaluated. Data set 1 and 2 were test set from EPANET and one real network. A sensitivity analysis was performed in the model. It was evaluated how optimal solution would change considering changes in population densities and attack risks.
The article concludes that the optimization approach proposed can effectively solve large-scale sensor-placement problems. However, different modeling structures exists considering different performance objectives, alternative placement locations, temporal effects, and sensor costs.
Discussion
The aspect that called my attention is this article and that I think it is a great contribution to this kind of problem is the use of sensitivity analysis. Due the uncertainties presented in some datasets, especially in water distribution systems, which obtaining data from water utilities is usually difficult, performing sensitivity analysis helps in validating the results. Future research could incorporate different temporal patterns and mobility data to better understand the variation in water demand during the day or even year.
Berry, J., Fleisher, L, Hart, W. Phillips, C. and Watson, J.-P. (2005) “Sensor Placement in Municipal Water Networks”, Journal of Water Resources Planning and Management, 131(3) pp. 237-243
This article addresses the issue contaminant events in water distribution systems. The motivation is higher vulnerabilities in water networks due its distributed geography. An approach for determining an optimal sensor configuration in water distribution systems is presented. The optimization method minimizes the expected fraction of population exposed to a contaminant event. Integer programming techniques was used. Four assumptions were used:
1) An attack occurs at a single point in the network
2) Total population exposed
3) Sensors protect downstream populations
4) Transitions between periods are ignored
Three data sets were evaluated. Data set 1 and 2 were test set from EPANET and one real network. A sensitivity analysis was performed in the model. It was evaluated how optimal solution would change considering changes in population densities and attack risks.
The article concludes that the optimization approach proposed can effectively solve large-scale sensor-placement problems. However, different modeling structures exists considering different performance objectives, alternative placement locations, temporal effects, and sensor costs.
Discussion
The aspect that called my attention is this article and that I think it is a great contribution to this kind of problem is the use of sensitivity analysis. Due the uncertainties presented in some datasets, especially in water distribution systems, which obtaining data from water utilities is usually difficult, performing sensitivity analysis helps in validating the results. Future research could incorporate different temporal patterns and mobility data to better understand the variation in water demand during the day or even year.
domingo, 15 de fevereiro de 2009
Assignment #4
Article Review
Lee, B. H. and Deininger, R. A. (1992) “Optimal Locations of Monitoring Stations in Water Distribution Systems”, Journal of Environmental Engineering, 118(1) pp. 4-16
The subject of this article is defining locations of sampling water quality in water distribution systems. The motivation of this problem is that U.S. EPA requires water quality monitoring prescribing sampling frequency and water-quality parameters. The sampling stations must be representative, but regulation doesn’t specify direct criteria on representativeness in water distribution system.
The authors bring the concept of coverage. Consider a water distribution network composed of nodes and pipes. Pipes convey water for demands in the nodes. For a specific node “i” there is a pathway that define upstream nodes. It is assumed that the water quality in upstream nodes can be inferred by the water quality of the node “i”. So, for a demand-fraction, the most downstream node used for sampling would represent better the water quality of the network.
A small example of network with 7 nodes is used to illustrate the concept and optimization model formulated. Using a integer programming code, the optimization model maximize coverage, for a specific number of sampling station, a water-fraction criterion and a demand pattern. Two study cases are analyzed: Flint, Michigan, and Cheshire, Connecticut. In this last case, different patterns on demand were considered, since demand is highly variable during a day. The coverage for this last example increased from 29.7 % to 45 %, considering 3 stations.
Discussion
The article presents a very interesting case of integer optimization model in water distribution systems, because it’s application in real systems. The formulation is very simple to understand, making the article an easy reading. Future applications, however could consider more refine water quality modeling.
terça-feira, 10 de fevereiro de 2009
Assignment # 3 - The Tragedy of the Commons
Article Review
Garrett Hardin, “The Tragedy of the Commons,” Science, 162(1968):1243-1248.
Garrett Hardin, “The Tragedy of the Commons,” Science, 162(1968):1243-1248.
Hardin begins his article with the idea that there is no technical solution for certain kinds of problems. The problem here is the “population problem” and the main idea is that it cannot be solved in a technical way. The followings paragraphs state that a finite world can support only a finite population, that the optimum population is not the maximum population possible and would it be the maximum good per person the right question, but what is good?
Then, Hardin brings the picture first sketched by a mathematical William Forster Lloyd, of a pasture shared by herdsmen, called “commons”. This example is used to exemplify how rational beings seeking to maximize its gains bring systematic negative effects that ruin all society. The article addresses some other interconnected issues like pollution and regulation.
Discussion:
Despite the article is a important reference in science in general, bringing into discussion the relevant issue of population growth and finite resources, I have some critics related to how the author have addressed the issue. The article states that the common doesn’t have rules and that anyone was free to do whatever it wants. This is not exactly correct with the concept of common according with economic science. Even if not formally defined, a society sharing a common will have cultural and habits that would characterize the behavior of the resources in a commons. Besides that, it seems to me unrealistic with the present world that a common could be exploited without any regulation.
Another issue apparently neglected by the author is the fact that human society is in evolution and development of new technology is constantly solving new problems. I do believe that in future, human societies can achieve a state of sustainability of human demands and natural resources.
segunda-feira, 2 de fevereiro de 2009
Assignment # 2 - Ground Water contaminant removal
Article Review in Linear Programming
The study case is located in Rocky Mountain Arsenal near Denver, Colorado. The contaminated ground water is result of military and industrial uses. The groundwater modeling was based in previous studies (Konikow, 1975, 1977, and Trescott et. al. 1976), which considered the two-dimensional flow in a heterogeneous isotropic aquifer. The solute transport was combined with groundwater simulation flow, based on the advection-dispersion equation. The objective of the modeling was to compute the field velocity in order to locate the plume boundary relative to the potential gradient control wells.
The stage II of the procedure is select best wells and rates of pumping/recharge, which was done by a linear programming approach combined with ground water flow simulation. The optimization framework minimizes the total pumping/recharge over time subject to hydraulic constraints that force the gradient to be toward the center contaminant removal well. The objective function and constraints are:
The main important results are the developed of a procedure for aquifer restoration. The procedure is general and can be applied in other situations. The author outlines two methodologies contributions: “the manner in which the problem is linearized and the extension of the concept of drawdown responses to hydraulic gradients responses”. The linearization was possible due the division of the problem into two parts.
Atwood, D. F. & Gorelick S. M. (1985). "Hydraulic gradient control for groundwater contaminant removal." Journal of Hydrology, 76. 85 - 106.
The article addresses the problem of contaminant ground water plume and proposes a two stage planning procedure to select the best wells and schedules to contain the contaminant plume, while a second system of wells removes the contaminated water. The study contemplates the use of linear programming, groundwater flow and solute transport simulation.
The study case is located in Rocky Mountain Arsenal near Denver, Colorado. The contaminated ground water is result of military and industrial uses. The groundwater modeling was based in previous studies (Konikow, 1975, 1977, and Trescott et. al. 1976), which considered the two-dimensional flow in a heterogeneous isotropic aquifer. The solute transport was combined with groundwater simulation flow, based on the advection-dispersion equation. The objective of the modeling was to compute the field velocity in order to locate the plume boundary relative to the potential gradient control wells.
The stage II of the procedure is select best wells and rates of pumping/recharge, which was done by a linear programming approach combined with ground water flow simulation. The optimization framework minimizes the total pumping/recharge over time subject to hydraulic constraints that force the gradient to be toward the center contaminant removal well. The objective function and constraints are:
where [R] = matrix of gradient response coefficients at gradient check locations; {u} pumpage vector; uc = pumping rate at central removal well; {v} = recharge vector; {e}T= row vector of 1’s; and {g} = known right-hand-side vector reflecting the target gradients.
The main important results are the developed of a procedure for aquifer restoration. The procedure is general and can be applied in other situations. The author outlines two methodologies contributions: “the manner in which the problem is linearized and the extension of the concept of drawdown responses to hydraulic gradients responses”. The linearization was possible due the division of the problem into two parts.
Assignment # 1b
Article Review in Linear Programming
Ilich, N. (2008). "Shortcomings of linear programming in optimizing river basin allocation." Water Resour. Res. 44.
The article has identified possible failures to solve a simple allocation problem using network flow algorithm (NFA). Two applications were tested. The first one was a reservoir with multiple outflows and the second one related to modeling of hydrologic channel routing.
The NFA searches a minimum cost flow in a network, which is represented by:
The NFA searches a minimum cost flow in a network, which is represented by:
where cij, lij, and uij are the cost per unit of flow, lower bound, flow and upper bound on flow along an arc(i, j). Constraints represent the mass balance at each node.
The test problem 1 “demonstrates breakdown of an iterative scheme on modeling a reservoir with two distinct outflow structures”. The outflow capacity is a function of water elevation in the reservoir. The water elevation, however is determined by the mass balance occurred in a time step. Therefore, the “NFA-based model must “guess” the final elevation for a time step in order to numerically integrate the average outflow capacity and thus estimate the upper bound on reservoir outflow”. The iterative procedure to converge to a guessed value may not achieve a good solution in complex systems with multiple reservoir and multiple outlet structures. The author proposes a method for linearization of reservoir outflow constrains in order to improve the described issues.
The test problem 2 addresses two issues related to use of LP and a hydrologic routing. “Hydrologic channel routing cannot be included in the LP-based models for a single time step optimization without violating the assumption of “demand driven reservoir releases”, which is the basic premise on which these models were built and on which they operate on a steady-state basis”. The second issue is the “inclusion of channel routing in multiple time step optimization framework may often require nonlinear representation of routing coefficients, since routing coefficients should be updated when channel flows change from low- to high- flow season”.
The author claims that none of the previous problems discussed can be overcome in a satisfactory way using LP framework, despite the fact that a suggestion of linearization was proposed for the first problem.
The author claims that none of the previous problems discussed can be overcome in a satisfactory way using LP framework, despite the fact that a suggestion of linearization was proposed for the first problem.
Discussion
Despite the fact that the article addresses specific issues related to the use of LP-framework, the article is interesting in the sense that brings awareness to the use of LP. Specifically, it discusses two important and common modeling procedures in water resources management studies, the first one a reservoir and the second one the inclusion of hydrologic channel routing. The article doesn’t propose definitive solutions for the problems, but well identified them and stimulate future research to better deal with them.
Future research would be the comparison analysis of these problems with different types of optimization frameworks, like for example, dynamic programming or evolutionary algorithm.
quinta-feira, 29 de janeiro de 2009
Assignment #1a
Article Review:
Liebman, Jon (1976) “Some simple-minded observations on the role of optimization in public systems decision making”. Interfaces 6(4) pp.102-108.
Main Ideas:
· “public systems problems are frequently ill-defined”;
· Optimization (or modeling, operation research, systems analysis) doesn’t work well in this kind of problem;
· Why? Fuzzy constraints and vague multiple objectives;
· It works in private-sector problems;
· In 1976 the optimization problem of river basin quality management was not successfully resolved;
· Analyst x Decision-maker: first one knows the tool, but doesn’t understand the results; the second one doesn’t know the tool, but have experience to understand results;
· Before 1976: “either it is linear or I can’t do it”;
· Science x Engineering: “If I do this, what happens?” x “If I want that to happen, what should I do?”;
· Inability to understand is inherent in any model;
· Conflicts among members of society are always present;
· Wicked problems: optimization can sort a set of alternatives;
· “the role of optimization and modeling is the formulation of alternatives rather than the selection of one of them”;
· A model is a way of communicating one's image of a problem, of what factors are important and how they interact;
· “A model is not unique. Since perceptions of wicked problems are widely different, goals and acceptable solutions are also diverse”;
· “Model is a message”. It’s difficult to transfer the understanding to others;
· “the process of modeling is a particularly rigorous form of thinking.”
Discussion
The paper is interesting since it brings to discussion the real applicability of modeling and optimization techniques. The author states that the use of optimization in public systems problems involves more complex issues than in private sector, due fuzzy constraints and multiple objectives. However, optimization and modeling, for these particular problems, should be used to improve the knowledge of how the system works and to propose a set of alternatives that could be applied.
I think that the author could give more details referenced to the cited examples (urban firefighting and river basin quality management), and used them to better explain his ideas. It would be interesting to see applied examples of optimization in public systems problems that had used highly complex modeling techniques but has presented bad results once putted in practice.
In my opinion, the article brings in discussion a important issue related to public systems and is correct the idea that optimization and modeling can not solve and give the right answers for all kinds of problems. I believe that modeling is a exercise of understanding a systems, and the fact of building a model, even whether it doesn’t bring good results, helps and contribute to understanding and proposing good alternatives.
Liebman, Jon (1976) “Some simple-minded observations on the role of optimization in public systems decision making”. Interfaces 6(4) pp.102-108.
Main Ideas:
· “public systems problems are frequently ill-defined”;
· Optimization (or modeling, operation research, systems analysis) doesn’t work well in this kind of problem;
· Why? Fuzzy constraints and vague multiple objectives;
· It works in private-sector problems;
· In 1976 the optimization problem of river basin quality management was not successfully resolved;
· Analyst x Decision-maker: first one knows the tool, but doesn’t understand the results; the second one doesn’t know the tool, but have experience to understand results;
· Before 1976: “either it is linear or I can’t do it”;
· Science x Engineering: “If I do this, what happens?” x “If I want that to happen, what should I do?”;
· Inability to understand is inherent in any model;
· Conflicts among members of society are always present;
· Wicked problems: optimization can sort a set of alternatives;
· “the role of optimization and modeling is the formulation of alternatives rather than the selection of one of them”;
· A model is a way of communicating one's image of a problem, of what factors are important and how they interact;
· “A model is not unique. Since perceptions of wicked problems are widely different, goals and acceptable solutions are also diverse”;
· “Model is a message”. It’s difficult to transfer the understanding to others;
· “the process of modeling is a particularly rigorous form of thinking.”
Discussion
The paper is interesting since it brings to discussion the real applicability of modeling and optimization techniques. The author states that the use of optimization in public systems problems involves more complex issues than in private sector, due fuzzy constraints and multiple objectives. However, optimization and modeling, for these particular problems, should be used to improve the knowledge of how the system works and to propose a set of alternatives that could be applied.
I think that the author could give more details referenced to the cited examples (urban firefighting and river basin quality management), and used them to better explain his ideas. It would be interesting to see applied examples of optimization in public systems problems that had used highly complex modeling techniques but has presented bad results once putted in practice.
In my opinion, the article brings in discussion a important issue related to public systems and is correct the idea that optimization and modeling can not solve and give the right answers for all kinds of problems. I believe that modeling is a exercise of understanding a systems, and the fact of building a model, even whether it doesn’t bring good results, helps and contribute to understanding and proposing good alternatives.
sábado, 24 de janeiro de 2009
Assignment #0
Howdy!!!
My name is Marcio Hofheinz Giacomoni. I'm a PhD Student at Zachry Department of Civil Engineering, Texas A&M University (TAMU). I have enrolled the course CVEN 665 because water resources systems analysis is my research field. Also, because Dr. Zechman is my adviser. At this moment, my research is focused on sustainability of stormwater management. My future plan is to study the land use/cover change in the hydrology of a watershed, using agent based modeling (ABM).
My objective in this course is to study the most efficient tools to better understand and solve problems related with water resources management and planning.
What is critical thinking?
Critical thinking in my opinion is the ability to make logical and reasonable discernment in a particular matter. To do that, some steps are important: good observation, have the right notation in describing the problem, have multiple perspectives, ability to model the problem or the system the problem are “located”, knowledge in identifying the real question, ability in defining hypothesis and ability to validate the hyphotesis. What do you think? Make a critical thinking of my ideas... and let's discuss!!!
My name is Marcio Hofheinz Giacomoni. I'm a PhD Student at Zachry Department of Civil Engineering, Texas A&M University (TAMU). I have enrolled the course CVEN 665 because water resources systems analysis is my research field. Also, because Dr. Zechman is my adviser. At this moment, my research is focused on sustainability of stormwater management. My future plan is to study the land use/cover change in the hydrology of a watershed, using agent based modeling (ABM).
My objective in this course is to study the most efficient tools to better understand and solve problems related with water resources management and planning.
What is critical thinking?
Critical thinking in my opinion is the ability to make logical and reasonable discernment in a particular matter. To do that, some steps are important: good observation, have the right notation in describing the problem, have multiple perspectives, ability to model the problem or the system the problem are “located”, knowledge in identifying the real question, ability in defining hypothesis and ability to validate the hyphotesis. What do you think? Make a critical thinking of my ideas... and let's discuss!!!
Assinar:
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