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Reservoir Operating Studies 2040 Demand Conditions without Elkhead Enlargement Project Key Assumptions The future "without project" conditions scenario was defined by the use of projected demands representing year 2040 conditions. These projected demands result in additional depletions, over the "current potential" demands represented in the scenario discussed above, of approximately 38,000 af. This 38,000 of is assumed to reflect depletions resulting from the activities that have already undergone Section 7 consultation as well as future uses not anticipated in previous Section 7 consultations. Thus the 38,000 of includes the depletive effects of activities considered in previous consultations, although the precise patterns and locations of those activities may be somewhat different from these assumed in the consultation process. Included in the 38,000 of demand increment is approximately 14,000 of of additional demand associated primarily with municipal use. The remaining 24,000 of of demand is associated primarily with industrial uses such as the construction of additional thermal-electric generation capacity at the Hayden and Craig stations, a new coal-gasification plant, new mining facilities and minor increases in agricultural and snow-making water uses. In most instances, these future depletions would be expected to occur using existing water diversion facilities and water rights. Some modeled future depletions may involve federal actions (e.g., permitting) that would require consultation under Section 7 of the Endangered Species Act. Elkhead Reservoir was modeled with a capacity of 13,700 af, as in the current conditions scenario. With the exception of the demand level, all modeling assumptions and reservoir operating rules were the same as those defined in the current conditions scenario. Results Water Deliveries Total basin water shortages are more frequent in this model scenario than in the current conditions scenario, occurring in 38 of the 53 years in the study period. Average annual total shortage is 1,598 of and the maximum annual total shortage is 15,721 of occurring in 1934. Most shortages are to agricultural demands though shortages to the coal-gasification plant are also frequent. Municipal shortages occur only in Water Year 1934. Reservoir Levels Figure 2-2 shows the end-of-month contents of the three modeled reservoirs. An increase in storage draft is evident in all reservoirs, but is most noticeable in Elkhead Reservoir. In 1934, the power contract pool in Elkhead is significantly depleted and there are fairly regular drafts on that supply in other dry years. Stagecoach experiences somewhat greater drawdown in dry years, due mainly to increased municipal releases, though the annual cycling is still dominated by winter hydropower and environmental releases. 2-16