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<br />Flood Control <br /> <br /> <br />Total intlow during 1985 was again <br />greater than normal for most of the <br />reservoirs in the basin. In the Upper <br />Basin, Navajo and Blue Mesa Reservoirs <br />are operated for flood control by provid- <br />ing space to store snowmelt floods. <br />Although Flaming Gorge and Glen <br />Canyon Reservoirs have no specifically <br />assigned flood control requirements, they <br />are operated so as to reduce the possi- <br />bility of spills. The space they provide <br />may be counted as part of the flood <br />control space at Lake Mead that is <br />required by the Army Corps of Engineers <br />(Corps) flood control regulations. <br /> <br />During 1985, the Upper Green River <br />jrainage received less than normal runoff <br />Nhile the rest of the Upper Basin drain, <br />3ge received above normal flows. The <br />3unnison River flows were less than <br />1984, but still above normal while the San <br />Juan River above Navajo was greatly <br />,bove normal In 1985 (184 percent of <br />lormal). As a result of the wide variability <br />)f flows over the Upper Basin, only the <br />;an Juan River below Navajo Dam had <br />lows higher than those in 1984. The <br />naximum 1985 discharges below the <br />Jams on the Gunnison and San Juan <br />1ivers were less than halt of the 1 984 <br />leak inflows. The Green River below <br />:Iaming Gorge experienced normal runoff <br />latterns. <br /> <br />.ake Mead is the only reservoir on the <br />:Olorado River in which a specific space <br />s exclusively allocated for mainstem <br />cod control. Flood control regulations for <br />"oover Dam have been updated and <br />3vised based on findings of a joint study <br />litiated in 1977 by Reclamation and the <br />:Orps with consultation and advice of <br />.tate and local interests. <br /> <br />, final report dated July 1982 which <br />ummarized the study findings and <br />,commended a new flood control <br />peration plan for Hoover Dam was <br />,leased July 1983. Vacant flood control <br />!orage space will be maintained in Lake <br />fead as stipulate a in the Report's Field <br />lorking Agreement between Reclama- <br />)n and the Corps for flood control <br />)eration of Hoover Dam and Lake <br />lead. These regulations establish <br /> <br /> <br />releases in a manner that maximizes <br />pUblic benefits in the United States with <br />reasonable consideratiOn for conditions in <br />Mexico. <br /> <br />Lower releases this year than the 25,000 <br />cts to 35,000 cfs levels during 1984 and <br />the 40,000 cfs to 45,000 cfs levels during <br />water year 1983 have avoided any addi- <br />tional significant damages along the river <br />in the Lower Basin. Scour in some <br />reaches of river channel has continued to <br />occur, and therefore river levels have <br />been lower in some areas than they were <br />with the same release levels during the <br />last 2 years. In a few areas, however, <br />reaches have refilled due to heavy sedi- <br />ment loads. One example is the reach <br />below Cibola Valley in the Lower Basin. <br /> <br />Total Colorado River reservoir system <br />storage at the start of water year 1985 <br />was approximately 57,332,000 acre. feet <br />and about 55,514,000 acre-feet at the <br />end of the water year, representing a <br />1,808,000 acre-foot increase in total <br />remaining available reservoir space. <br /> <br />In addition to the mainstem structures, <br />Alamo Dam on the Bill William River, and <br />Painted Rock Dam on the Gila River (both <br />in the Lower Basin) received flood inflow <br />during water year 1985. During water <br />year 1986, Painted Rock and Alamo <br />Reservoirs are scheduled to be operated <br />in accordance with established flood <br />control criteria to maximize the available <br />flood control space remaining in these <br />reservoirs. <br /> <br />23 <br />