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1 Reservoir Operating Studies 1 1 I J does the "current potential conditions with consulted depletions" scenario used to develop the preliminary -flow recommendations at Maybell. Water demands in this scenario are met using existing direct flow water rights and, if necessary, storage deliveries from the reservoirs. All reservoirs are represented at their present capacities. There is no mainstem instream flow right in place nor are there any reservoir operations to enhance mainstem flows at any locations. Scenario Results Water Deliveries Water shortages to demands occur in 34 of the 53 years of the study period in this scenario. However, all of these shortages are to agricultural demands, many of them on small tributaries, that have no storage supplies. The average annual total shortage is 917 of and the maximum annual total shortage is 11,773 of occurring in 1934. ' Reservoir Levels There is very little use of reservoir storage in this scenario because the demands with ' storage contracts can be met from direct flow supplies in all but the driest years. Figure 2-1 shows the end-of-month contents of the three modeled existing reservoirs. As can be seen, there is little draft for water supply purposes except in the dry periods of the 1930's, `50's, and ' `70's. The regular annual cycles that are evident are the result of evaporation and, in the case of Stagecoach Reservoir, winter releases for power generation and environmental purposes. ' Instream Flow Conditions Flows below Stagecoach Reservoir reflect hydropower and environmental releases from that facility. These operations tend to produce more uniform flow conditions year around, with only slightly elevated (on the average) flows during the runoff period. Streamflow conditions below Steamboat Lake and Elkhead Reservoirs primarily reflect the spring spilling of inflows, because those reservoirs are full most of the year, and low fall and winter flows because the ' reservoirs do not presently have minimum release requirements. Note that seepage from Elkhead Reservoir has not been explicitly modeled. ' Table 2-5 shows modeled flow conditions at the Maybell gage. The seasonal dependence on snowmelt runoff is clearly evident, as are the late season effects of upstream depletions. Note that the occurrences of zero flow are an artifact of the modeling process; in reality, the Maybell Canal diversion dam just upstream of the gage reach exhibits some leakage that keeps a small amount of flow in the river; this seepage phenomenon was not represented in the basin model. Flow conditions at the Maybell gage site can be used as a general indicator of Yampa Raver flow conditions in occupied habitat above the confluence with the Little Snake River, though there are reach gains and return flows which accrue below the Maybell gage. Table 2-6 presents a statistical summary of modeled flow conditions at Maybell that can be compared to the preliminary flow recommendations. Noteworthy are the low flows in late summer and fall 2-12