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<br />Actual Operations under <br />Criteria-Water Year 1977 <br /> <br /> <br />Operations of the Colorado River system during <br />1977 were greatly affected by the drought condi. <br />tions in the western part of the United States that <br />spread into the Colorado River drainage area in the <br />fall of 1976 and continued through water year <br />1977. Precipitation accumulations in the Upper <br />Basin for the first 6 months of the water year were <br />only 39 percent of normal and snow measurements <br />on April I. 1977, indicated only 41 percent of a <br />normal snowpack. Starting January 1. the snow. <br />melt runoff forecast indicated a water supply con. <br />siderably less than normal that would allow a sched. <br />uled release of only B.23 million acre.feet from the <br />Upper Basin at Lake Powell for the water year. <br />Releases from the other reservoirs through Sep. <br />tember 1977 were scheduled accordingly to meet <br />the power production and other multiple purpose <br />requirements of the system. At the beginning of <br />each month thereafter through June. the forecast' Ground ...ter for irrigation of crops. <br />was revised based on precipitation and snow data <br />collected during the month and the scheduled op- <br />eration was revised accordingly. <br /> <br />The Colorado River Basin runoff at Lake Powell for <br />water year 1977 was 3,217.000 acre.feet, or 27 <br />percent of the long.time average. This was the low. <br />est recorded runoff on the Colorado River at the <br />Lake Powell site in the 72-year period of record. <br />Precipitation in tile Colorado River Basin for water <br />year 1977 was 65 percent of normal. The major <br />storage reservoirs on th" Colorado River system <br />stayed within the normal operating range during <br />water year 1977 and the downstream water reo <br />quirements were met from carryover reservoir <br />storage. Aggregate storage at the end of water year <br />1977 was 42,141.000 acre-feet which represented <br />a decrease of 5.671 ,000 acre-feet from water year <br />1976. <br /> <br />A description of the actual operation of each of the <br />reservoirs in the Colorado River Basin follows. <br />Charts I through 10 show hydrographs of monthly <br />outflow from the reservoirs and water surface ele. <br />vation and active storage in the reservoirs for water <br />year 1977. <br /> <br /> <br />Corn crop in the Salt River Project, Arizona; <br />Reclamation's first large multipurpose water resources project. <br /> <br />I <br />