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through the reservoir. The reservoir would need a refill right to operate this way and a filing for <br />a junior appropriation would need to include this provision. <br />With a diversion capacity of 300 cfs a firm yield of 132,000 af is attained; 30,300 af (23%) of <br />water is available for M&I use, and 20,800 af (the remainder of the volume) is available for the <br />uniform power demand. The reservoir's critical drought is the "1977" drought, with the reservoir <br />being less than full from July 1976 through February 1980. <br />2. Results — Smaller Reservoir (Alignment 2) <br />Firm yield for the smaller reservoir impounded by dam Alignment 2 was shown to be 54,500 af, <br />and there was no benefit to increasing diversion capacity above 115 cfs. Smaller diversion <br />capacities and firm yields were not explored because meeting the OMID demand (58,300 af/yr) <br />seems to be a reasonable threshold for viability of the project. When annual demand is set to <br />58,300 af/yr, it can be met in every year of the 31-year modeling period, except for 197�, when <br />it delivers approximately 51,000 a£ Whether this represents an acceptable level of risk to OMID <br />is not known. Raising the diversion capacity from 115 cfs provides no benefit because during the <br />critical period, legally available water does not exceed this amount; the reservoir capacity, that <br />is, the water in storage at the beginning of the critical period, is too small for the total volume of <br />the deficit with respect to demand over the critical period. <br />3. Limitations to the Yield Analysis <br />Actual firm yield for the project may be less than predicted by the spreadsheet models, due to the <br />conceptual nature of this study and the need to work with readily available data and information. <br />Some identifiable simplifications in this analysis, which can be improved if the project proceeds <br />to more rigorous analysis, include the following: <br />• The CDSS Gunnison River Baseline Model has not been updated to include the National <br />Park Service's instream flow reserved right in the Black Canyon of the Gunnison, which <br />was finalized in January, 2009. The NPS water right reach does not extend to the Grand <br />Valley Canal headgate, so water that is released or bypassed by the Aspinall Unit to <br />maintain the NPS flows would be divertible when it reaches the diversion site. However, <br />whether flow increases would occur at times the project could take advantage of them is <br />not clear. 'The instream flow reserved right will probably not significantly change the total <br />annual volume of flow at the Grand Valley Canal headgate, but it will re-time the water. <br />The components of the instream flow reserved right that relate to peak flushing flows are <br />likely to increase flow at the diversion during periods when flows are already high, and <br />the diversion is operating at full capacity. In addition, any water rights currently being <br />45 <br />AECOM <br />� 2/22/10 <br />