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1984 Colorado River Operations Studies <br /> • Study Plan <br /> SECTION I - OVERVIEW <br /> 1.1 Need <br /> In 1983, an unusual and unpredictable combination of events resulted in the <br /> largest spring runoff in the Upper Colorado River Basin in over 60 years. <br /> Snow accumulation and runoff forecasts through May 1, 1983, were generally <br /> only slightly above normal. In May, however, a series of late storms dumped <br /> heavy additional snow in the basin, and cool temperatures resulted in little <br /> runoff until late in the month, when a sudden drastic warming trend caused <br /> rapid snowmelt and very heavy runoff. Continued hot weather in June, plus <br /> basin wide heavy rains in mid-June, created a very efficient runoff con- <br /> dition where most of the accumulated snowpack melted quickly and thus a <br /> smaller amount than normal was lost to evaporation and infiltration. Runoff <br /> forecasts were revised upward almost weekly from mid-June on, with a final <br /> forecast of 14.6 million acre-feet (maf), about 210% of normal April-July <br /> inflow to Lake Powell, issued on June 28. This sudden heavy runoff resulted <br /> in spillway flows at both Glen Canyon and Hoover Dams, and required maximum <br /> releases from Davis Dam of about 44,000 cubic feet per second (cfs). While <br /> those flows along the lower Colorado River were less than the levee design <br /> flow, considerable flooding occurred to properties located on the flood <br /> plain inside the levee system. The large spillway flows damaged the <br /> spillway tunnels at Glen Canyon and Hoover Dams. High flows along the river <br /> continued through the summer of 1983 and did not recede to non-damaging <br /> levels until the fall. The President declared the areas affected by the <br /> flooding a disaster area. <br /> Although a General Accounting Office investigation and Congressional <br /> hearings found that Reclamation had operated the reservoir system in accor- <br /> dance with existing criteria and regulations, numerous suggestions have been <br /> made to reassess current operational policies and evaluate various alter- <br /> natives. There is the need for a tool to use in making operational deci- <br /> sions during the current full reservoir system condition when average annual <br /> basin runoff is expected to continue to exceed demands for at least the next <br /> several years. <br /> 1.2 Objective <br /> A reassessment of the operation of the Colorado River will involve the defi- <br /> nition of feasible alternative operating strategies and a standard method <br /> for quantifying each strategy in terms of risk, water supply, flood control, <br /> and power generation. Those methods and data will not only be useful in <br /> assessing various operational strategies, but will also be used as the basis <br /> • <br />