Laserfiche WebLink
<br />. . . <br /> <br />, , <br />, <br /> <br />to estimate annual shared CRSP evaporation based upon yearly reservoir storage volume <br />(surface area). The 1988 Hydrologic Determination considered variations in. shared <br />CRSP reservoir evaporation with storage for conducting statistical trace analyses to <br />. evaluate possible frequencies and magnitudes of shortages; however, it deducted a long- <br />term average shared CRSP reservoir evaporation of 0.52 maf per year from the critical- <br />period Upper Basin yield of at least 6.0 maflyr to determine the amount of water <br />available for Upper Basin uses through the critical period. . <br /> <br />C. Results <br /> <br />Mass balance analyses were performed for various Icombinations of storage, Lower Basin <br />deliveries and overall shortages to evaluate the allocation of water to the Upper Basin <br />(see mass balance analyses provided in Appendix A). The following is a summary of the <br />results of the analyses: <br /> <br /> Minimum Yield Yield with <br /> Lower Basin without 6% Overall <br /> Delivery Shortages Shortages <br />Storage Assumption UM!ll !m!fi !mift <br />Maintain minimum power pools 8.25 5.55 5.79 <br /> 7.50 6.30 6.57 <br />Use minimum power pools 8.25 5.72 5.98 <br /> 7.50 6.47 6.76 <br /> <br />The yield for this analysis is defined as the amount of water available at Lee Ferry for <br />use, on average, by the Upper Basin, exclusive of shared CRSP reservoir evaporation. <br />Shortages in the above table are defined as 6 perc:ent or less overall computed shortage <br />for any period of 25 consecutive years consistent with the 1988 Hydrologic <br />Determination. Results are shown for minimum Lower Basin deliveries of 8.25 maf and . <br />7.50 maf as was done in the 1988 Hydrologic Determination. The analyses in this <br />investigation should not be construed to prejudice the positions of either the Upper <br />Colorado River Commission or the States of the Lower Division as to the interpretation <br />or administration of Article ill of the Colorado River Compact. <br /> <br />For those analyses that use an allowable or tolerable overall shortage of 6 percent or less <br />of the use over any period of 25 consecutive years, the results indicate that there would <br />be 5 years of shortage to meet all demands on the Upper Basin out of 95 years of record <br />used in this investigation. However, the annual amounts of computed shortages for those <br />five years would not fully materialize because Upper Basin consumptive uses will be <br />below average under critical-period hydrology due to physical water supply shortages at <br />the sites of use in the Upper Basin. For example, the natural flow at Lee Ferry for 1977 <br />was only 5.55 maf, and severe water supply shortages occurred throughout the Upper <br />Basin in that year. The computations of shortage in this analysis give conservatively <br />large estimates of annual shortages at Lee Ferry and do not fully reflect all factors, <br /> <br />4 <br />