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<br />e <br /> <br />e <br /> <br />e <br /> <br />- <br /> <br />UJ2~197 <br /> <br />e <br /> <br />1984 Colorado River Operations Studies <br /> <br />Study Plan <br /> <br />SECTION I - OVERVIEW <br /> <br />" <br /> <br />1. 1 Need <br /> <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 DOrmal 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 /> <br />.I' <br /> <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 /> <br />1.2 Objective <br /> <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 />