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Show 5.6 Summary A compact optimization model was developed to aid decisions on the selection and sizing of promising reservoir sites from a candidate list. The model can be applied to any general configuration of reservoirs in series or parallel, with flow diversions, yields for M& I, irrigation and hydropower, flood and conservation storage and recreation benefits considered. The model was exemplified with data from the Lower Bear river and Jordan river basins. The model developed is computationally more efficient than other algorithms that embody the same problem scale and level of generality. This was achieved through a decomposition of the model into simulation and optimization components. The main limitation of the model ( in the form used for the applications), is the need to pre- specify yield reliabilities over a critical period, and the associated simple reservoir operation rule. Where the region of application is hydrologically homogeneous ( common critical period) this limitation is not significant. In other situations, modifications to solve for year by year reliabilities as indicated in section 5.3.8 are advisable. More sophisticated joint reservoir operation rules can also be accommodated in the simulation component of the model. It should be noted that since they are applied on a reservoir by reservoir basis, the success of the modified sequent peak and the hydropower generator sizing procedures, is contingent only on the specification of a vector of inflows and releases at an individual reservoir. Thus the simulation component of the multi- reservoir model can be readily modified to address alternate joint operation rules. The Lower Bear River applications considered a multi- reservoir, multi- purpose reservoir system, with yield failures permitted for M& I and irrigation, and diversions to an off- stream reservoir downstream of a set of reservoirs in series and parallel. Applications were performed with 2 reservoirs in series, 2 reservoirs in parallel, and 7 reservoirs ( including those in the previous applications) in series and parallel. The applications demonstrated that the model is responsive to the configuration of the reservoirs and to the demands placed. The solutions obtained when the applications were performed with the full set of reservoirs showed a modification of results from the applications where only 2 of the reservoirs comprised the system. This reflected the potential for obtaining some of the yields from the newer reservoirs in the system, and the feasibility of providing increased regulation upstream to reduce storage at the downstream reservoir. The most promising reservoir sites appear to be Amalga and Honeyville. The Oneida and Millcreek sites also appear to be promising. The E. Promontory site indicated a very high benefit- cost ratio, largely because of the high benefits assumed for the bird refuge, and low storage costs. The Avon site appeared rather marginal economically. The Jordan river basin applications considered a single purpose ( M& I use), and considered water treatment costs in addition to the other costs. Seven new sites in addition to the existing Mountain Dell reservoir were considered. The Little Dell site was upstream of the Mountain Dell reservoir. All other sites were in parallel. Yield failures were not considered, and only a firm yield ( no value for secondary yields) was considered. The, model's performance was once again heartening. It appeared to properly account for the interactions between the yield and storage capacities needed at the sites in series ( Little and Mountain Dell) and in parallel ( yields were developed one or two reservoirs at a time, as demand was increased, with yields increased across sites in a manner roughly proportional to the marginal costs of yield at each site). The Big and Little Cottonwood sites were indicated to be the most promising, with a lack of preference exhibited for the development of the Little Dell site. The development of an annual firm yield of 80,000 acre- feet from 153 |