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Summary of Evaluation of Alternatives Three of the alternatives considered in the analysis, Alternatives III-A, Ill-E. and III-F, could develop more water than any of the other alterna- tives. Alternative III-A was estimated 10 yield 102,000 acre-fget per year for release from storage. with 34,000 acre-feet being delivered for use after conveyance losses. Alternative III-E was estimated to develop approxi- mately 200,000 acre-feet per year for release from storage, with 160,000 acre-feet delivered to the Republican River Basin. Alternative llI-F would develop 191.000 acre-feet per year, and recharge 63,200 acre-feet into the South Platte River alluvial sys- tem: of that, an estimated 42.200 acre-feet would be recovered. The expansion of an existing down- stream mainstem storage facility (Allernative III-D) or the construction of a new storage facility on a plains tributary (Alternative IV-A) would result in the smallest amount of water being developed and delivered for use. Potential water development in the upper mainstem part of the basin or on mountain tributaries would, in general. require a much greater fi- nancial commitment in terms of construction costs and interest during construction. This is indicated by the estimated investment costs shown for Allernatives I-B and II-A. Aller- native I-B. as described for purposes of this study. would require an in- vestment of over $1 billion. Aller- native I-C, management changes of existing facilities, was assumed to require no initial investment to pro- vide a municipal watersupply. Pres- ent storage allocated to water con- servation or flood control would be converted to municipal water supply storage. Alternative II-A includes a hyrdoelectric power component re- sulting in some of the larger initial investment costs. 12 In all cases except Alternative I-C, the net economic benefit is estimated to be negative; i.e., the present value of project costs exceeds the present value of project benefits. Alternative I-B would involve the construction of new off-channel storage facilities to store upstream mainstem flows and has the lowest net economic benefit. Allernative I-C is the only alternative with a positive net eco- nomic benefit ($6.3 million). because it was assumed to require no initial investment. The analyses presented in this study showed estimated costs exceeding benefits; i.e., the benefit. cost ratio was less than 1.0 for every project except Allernative I-C. (No benefit- cost ratio could be estimated for Alternative I-C beca use no costs were associated with this project.) The One project which contains a hydro- electric power component, Alterna- tive II-A, has the highest benefit- cost ratio. Projects which involve an expansion of existing facilities, Al- ternative I-D and II-D, would require a much smaller initial investment and demonstrate a relatively larger benefit-cost ratio than the other alternatives. Most of the alternatives were esti- mated to provide small positive changes from present water quality conditions. The only exception is for Alternative Ill-E, which may cause a large negative change in water quality conditions in the downstream mainstem South Platte River, because a large volume of water would be diverted from the South Platte River Basin and exported into the Repub- lican River Basin. Alternative I-A may cause a large negative change from present fishery conditions within a reach of the upstream mainstem South Platte River. The construction of an up- stream mainstem reservoir would eliminate part of the cold water river- ine fishery and replace it with a stocked reservoir. Development fa- cilities outlined for Alternative II-A also may cause a large negative change from existing conditions. In contrast, the expansion of existing facilities (Alternatives I.D, II-D, and III-D,) would cause small to moderate positive changes in existing condi- tions. The expansion of these reser- voirs may result In higher lake levels for longer periods, which would contribute to more productive fish- eries. Terrestrial wildlife also might benefit from these conditions.