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Reservoir Operating Studies ' Instream Flow Conditions Flow conditions below Stagecoach and Steamboat Lake are similar to the "without project" case. Flows below Stagecoach reflect the winter releases for power and environmental purposes and are relatively stable throughout the non-runoff season. Flows below Steamboat Lake reflect seasonal spilling from a full reservoir and no minimum release operation. ' Flows below the enlarged Elkhead Reservoir are dramatically different from previous scenarios. The effect of the operation of the enlarged reservoir is to shift the outflow hydrograph towards the late summer and early fall months when releases are made help meet flow targets at Maybell. Peak flows during April through June are lower as runoff is capture and the enlarged reservoir fills. Figure 2-4 presents a comparison of average monthly flows in Elkhead Creek downstream of the reservoir under 2040 demand conditions with and without , the project. Flows at Maybell are similarly affected by the enlargement of Elkhead Reservoir. As shown in Table 2-9, flow support releases from the enlarged Elkhead Reservoir increase late summer and fall flows to values greater than or equal to the defined flow targets (Table 2-8). In the month of September, median flows with project operation are 200 cfs. This is ' significantly greater than flows under current potential conditions (112 cfs) and under the 2040 "without project" case (61 cfs). In fact, the flow support release strategy is able to achieve a median flow regime equal to the preliminary flow recommendations in all months except July. , More noteworthy, however, are the improvements in dry years (75th percentile flows). The flow support strategy achieves a September flow of 200 cfs versus 44 cfs under current potential conditions and 6 cfs under the 2040 "without project" case. Table 2-9 Modeled Flows at Maybell at Projected 2040 Demand Level With Project (cfs) Month 25% exc. 50% ex c. 75% gxc. October 276 204 204 November 332 255 223 December 303 228 175 ' January 269 217 164 February 310 256 218 March 669 498 363 April 2,840 1,869 1,147 ' May 6,810 5,666 3,764 June 6,312 5,103 3,585 July 1,693 938 401 August 328 220 220 September 200 200 200 During the spring and early summer months, flows in the Yampa River at Maybell are less than "without project" operation. This is a result of the additional water storage capacity of the enlarged Elkhead Reservoir and the fact that the reservoir is typically drawn down over the fall and winter months to make flow support releases. However, these reductions in 2-22