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I I I I I I I I I I I I I I I I I I I Gunnison Tunnel diversion demands are consistently met and Blue Mesa Reservoir releases are able to maintain the target 300 cfs minimum instream flow in the Black Canyon under Scenario 2B. 6.3 SCREENING OF ALTERNATIVE PLANS The six alternative plans were screened by the Study Team and reviewed by the Authority, the project sponsors, the Technical Steering Committee, and the Advi sory Committee. The following screening factors were used: abil ity to meet target objectives; environmental effects; potential benefits; institutional/ social factors; and cost. Table 6.5 presents a summary of the screeni ng results. The rel at ive rank assigned to each alternati ve pl ans is presented below: Plan Rank A lternat i ve 5 1 A lternat i ve 6 2 Alternative 1 3 Alternative 3 4 A lternat i ve 4 5 A lternat i ve 2 6 Alternative 5 was selected as the top ranked plan mainly because it meets the target objectives in a balanced manner with relatively few adverse environmental impacts. The two reservoirs included in this alternative would be able to reduce the total average annual irrigation depletion shortage in the Study Area by about 60 percent. Furthermore, the hydrologic model results indicate that the reservoirs can provide releases to meet enhanced streamflow targets below each dam and would have reservoir fluctuations which would allow the development of a flatwater recreation facility at each reservoir. Both reservoirs could alleviate flooding which takes place periodically. Although the No-Action scenario did not identify any M&I shortages in the study area, the water that is stored for the purpose of instream flow enhancement could possibly be stored under a transferred City of Gunnison storage decree. This 6-5