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Executive Summary water rights, i.e. the Maybell Canal and the proposed Juniper Canyon instream flow right, to allow additional upstream junior diversions. The amount of water that could be exchanged out of the Williams Fork Reservoir was limited in the model by imposing a minimum instream flow to prevent the Yampa River from being dried up in some occupied habitat reaches (specifically the mainstem above the Williams Fork) during the months of August and September. The amount of this minimum instream flow constraint was suggested by the Service and represented in the model as 150 cfs in August and 110 cfs in September. There were no such constraints on exchange potential in other months or for other reaches. Shortages occurring in Scenario V for the existing senior demands were identical to those observed in Scenarios I through IV. Shortages to existing junior demands and to future demands were higher than in Scenario IV but substantially smaller than Scenario III. Modeled shortages under Scenario V are summarized in Table S-5. Williams Fork Reservoir remained relatively full over the study period and on only two occasions briefly dropped below 60,000 af. The potential to exchange water up the Yampa River was occasionally limited by either the natural flows or the minimum flow constraints specified in the model. This placed more burden on Elkhead Reservoir to meet the Craig area demands than occurred in Scenario IV. The result was an increase in the draw on Elkhead over that of Scenario IV and greater fluctuations in storage levels than in Scenario IV. Table S-5 Summary of Modeled Demand Shortages Over 53 Year Study Period Demand Level Scenario I Scenario II Scenario III Scenario IV Scenario V Potential 1989 Maximum' 7,782 9,026 5,841 822 3,379 Average2 312 4,062 1,955 58 700 Projected 2015 Maximum' 9,819 12,613 6,413 822 4,974 Average2 362 4,517 2,084 58 742 Projected 2040 Maximum' 17,024 37,246 21,526 6,629 8,897 Average2 849 15,093 6,340 247 1,503 Notes: 1 - Sum of maximum annual shortages to each demand over entire study period. 2 - Average annual shortage to all demands. Environmental Considerations Instream Flows An important aspect in formulating near and long term water development projects and strategies as part of the Feasibility Study was the consideration of fisheries and other wildlife. Of particular concern were stream flows predicted for the Yampa River mainstem in occupied habitat areas of the endangered species. The modeled effect of administration of the Juniper S-22