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Show Chapter 7 Screening Models for Reservoir/ Groundwater Development Extensions of the reservoir screening model developed in Chapter 5 to consider groundwater development are presented in this chapter. Two situations are of interest. The first considers groundwater as an alternate source of supply to reservoir development. The viability of building a reservoir in lieu of increasing groundwater development is explored. A simple extension to the reservoir screening model developed in Chapter 5 is proposed. It is presumed that either the reservoir system or the groundwater resource is to provide the desired yields with the specified degree of reliability. Augmentation of reservoir yields with increased groundwater pumping during failure years is not considered. Parametric applications of this model to the Jordan River Basin are presented. The second situation considers reservoir development with conjunctive use of surface and groundwater. Yield failures for reservoirs in critical years are allowed. The degree of failure in these years is compensated for by increased groundwater pumpage such that the specified reliability of the system yield is met. An integration of the models presented in Chapters 3 and 5 is used to develop the model in this case. Two example applications of this model with data from the Jordan River Basin are presented. 7.1 Model with Surface and Groundwater as competing resources The basic assumption in this model is that groundwater and surface water are distinct resources that compete for utilization, when new development is considered. The main concern addressed is whether new supplies should be developed using groundwater or through the construction of a set of reservoirs. The only linkage assumed between the groundwater and surface water systems is that of demand. A yield formulation is adopted for the analysis. Where a firm yield is considered for the groundwater system, the uniform annual demand pattern assumed for groundwater supply in the Chapter 3 applications is relevant. Since no interactions between the surface and groundwater resources were considered, it was presumed that groundwater usage in this screening model could be used as an aggregate variable ( rather than individual well pumpages). Results from the parametric applications of the kind performed in Chapter 3 could then be used to define a relationship between annual cost and aggregate uniform annual groundwater usage for the demand areas. The water rights, drawdown and water quality constraints associated with the groundwater formulation would thus be implicitly satisfied. The Reservoir/ Groundwater screening model then extends the reservoir screening model presented in Chapter 5 by adding decision variables GRm and GRj that represent the groundwater yield supplied by aquifers in M& I demand area m, and an irrigation demand area i. These variables appear in the objective function of the model and in the demand constraints. The model is then stated symbolically through equations 7.1 through 7.5 below and equations 5.13 through 5.16 and 5.19 through 5.21. The PSLP algorithm was once again used for solutions of this nonlinear optimization model. 164 |