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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />002503 <br /> <br />decrease occurs in July and averages about -3.5 feet before constrained operations and occurs <br />in October and averages -3.5 feet after. The maximum to minimum monthly range of values <br />is greater before constrained operation than after, but is also influenced by the greater <br />number of years observed before constraints were initiated. <br /> <br />Historical Parker Dam/Lake Havasu Operations <br /> <br />Figure E15 shows the mean daily releases for Parker Dam. There are 365 daily mean values <br />plotted for each year. The maximum non-flood year mean daily release is shown to be <br />16,800 cfs during April 1989 and corresponds with high downstream water use demands. <br />The minimum mean daily release of30 cfs occurred during January 1995 and was due to <br />10wering of Bureau of Indian Affairs operated Lake Moovalya for maintenance of the <br />Colorado River Indian Tribes diversion canal. Releases from Lake Moovalya were made to <br />meet normal downstream water use demand. <br /> <br />Figure E16 shows how the 2,920 (365*8 years) mean daily releases of Figure E15 are <br />ranked. For example, 40 percent of the daily releases were less than 8,200 cfs. <br /> <br />Figure E17 shows the average, maximum, and minimum mean daily Parker release in each <br />month for the 8 non-flood control years. For example, January average daily release is the <br />average of the 248 (8*31) mean daily releases or 4,000 cfs. The January maximum is the <br />highest of the 248 mean daily releases or 11,500 cfs and the minimum is the lowest of the <br />248 mean daily releases or 30 cfs. A visual inspection of the averages shows how releases <br />change during the year to meet downstream demands. Also noted is the maximum <br />instantaneous release for Parker Dam of 19,000 cfs. The minimum instantaneous release that <br />can be expected is about 30 cfs. Such low flows may be caused by downstream flooding, <br />construction, search and rescue, or for other emergencies. When comparing figure ElO <br />Davis average releases with figure E17 Parker average releases, the difference is mostly due <br />to change in storage of Lake Havasu, diversion by MWD and CAP, and inflow of the Bill <br />Williams River. <br /> <br />Figure E18 shows Parker Dam actual hourly releases for four days during 1994. The <br />release patterns for the different seasons show the pattern for power demand and that the <br />4 generating units are put on and off line as full units of approximately 5,000 cfs each down <br />to 1 unit. Generating units may each be reduced by up to 72 percent gate opening for <br />further regulation. As monthly releases for months of higher downstream water use <br />increase, the maximum hourly release tends to increase. <br /> <br />Figure E19 shows Lake Havasu midnight elevations. It shows that Lake Havasu tends to <br />reach its maximum elevation in late spring and its minimum elevation in the winter to <br />provide flood control space for large hurricane type storms coming up river from Baja <br />Mexico. Actual elevations differ from target elevations of figure 15, section II, as needed to <br />regulate Hoover and Davis releases and downstream demands for water. Lake Havasu' s <br />limited 4 foot operating range is now stressed to help meet the operating constraints on Lake <br /> <br />Appendix E - 5 <br />