Nishikawa, T., 1998, “Water-resources optimization model for Santa Barbara, California,” JOURNAL OF WATER RESOURCES PLANNING AND MANAGEMENT-ASCE, Volume: 124, Issue: 5, Pages: 252-263.
In this article, a simulation-optimization model were performed to minimize the cost of water supply, fulfill water demand, and control saline water intrusion from near ocean in Santa Barbara area during a drought. In this model, decision variables were water conveyances from surface and ground water and hydraulic head. Sensitivity of the model was also provided about demand, carryover, head constraints, and capacity constraints.
In detail about a formulation, to fulfill minimizing the water supply cost, a linear programming was employed. The objective is subject to maximum water-supply capacity, maximum and minimum heads along the cost, limits retaining pumping distributions among producing zones, recharge distribution, and water-supply demand constraints. The decision variables were amount of water delivered from surface water, ground water, and Cachuma Reservoir carryover. Additionally, to estimate the heads from pumping pattern, the response coefficient method was employed. MODFLOW method was also used for ground-water flow model.
After select constraints, there were three kinds of scenarios. First, in Base Case which is average monthly releases, the optimization scenarios optimally reached the minimum cost with satisfying all constraints. It means that cheapest water and inland wells would be used as much as possible. In other approaches which were current and prosed monthly Gibralter distribution, the result were not better but it showed that water distribution timing is really important to minimize the cost. In addition, through sensitivity analysis we can also know that additional saving will occur if seawater intrusion is acceptable.
Discussion : This article is interesting because it shows that how to use a linear optimization method for real problems and how to set complex variables and constraints in the linear approach. However, though components of this model were quite reasonable, it would be better if there were detailed constraints and variables such as maintenance or economic trend. In case of allowance of seawater intrusion, there should be environmental impact. For further study, I would like to add additional components mentioned above or other substitutions in this study.
I feel like Jaeyoung did a great job in summarizing the objectives and main points in this article. I agree with his statement that the environmental impacts due to salt water intrusion need to be clarified. No where in the paper does it state how much salt water intrusion is acceptable. I believe that this is something that should be studied and that there should be a cost associated with environmental impacts.
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