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<br />~'~~~, <br /> <br />". , ' .'," '" ",.",,,.,,, ""'fI" ,,\, -0,......, "'f-. 'rl~ oIll:i.. ~. fe. . <br />----,-..-.-~" ~., ~ "":" . "" . ~""".' - -'-"~,. ,~-" 1 <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />. <br /> <br />PROBABLE IMPACT OF PROPOSED RESERVOIRS ON SEVERAL <br />REACHES OF THE YAMPA RIVER IN COLORADO: <br />SUMMARY OF DISCUSSIONS <br /> <br />Carl F. Nordi n <br />Hydrologist, U.S. Geological Survey <br />Denver, Colorado, U.S.A. <br /> <br />BACKGROUND <br /> <br />Two reservoi rs are proposed by the Colorado Ri ver Water <br />Conservation District for construction on the Yampa River in Colorado. ~ <br />According to information received from the District's Public Affairs <br />Consultant (Lee Harris, personal communication, 1980), the upstream <br />reservoir, Juniper, will have a capacity of about 1.08 x 10' acre-feet <br />behind a 210-foot dam, at water surface elevation of 6125 feet. It will <br />have a total rated generating capacity of 98 x 103 kw and will generate <br />134 x 10' kw-hrs/year under a schedule for peaking power. Juniper Dam <br />will have a minimum release of 25 cfs (cubic feet per second) and the <br />capability of going to a maximum discharge of 7000 cfs instantaneously. <br /> <br />The downstream reservoir at Cross Mountain is are-regulating <br />reservoir to smooth the flows from the peaking opera ton at Juniper. It <br />will have a capacity of about 142,000 acre-feet at water surface eleva- <br />tion of 5875 feet behind a 260-foot dam and will have generating <br />capacity of 50 x 103 kw. It will generate about 165 x 10' kw-hrs/year. <br />Maximum outflow is about 3000 cfs.Proposed operating criteria call for <br />a minimum release of 200 cfs or a greater amount to provide a minimum <br />flow in the Yampa River below its confluence with the Little Snake River <br />of SOD cfs. During the rafting season, May through July, a minimum flow <br />of 1800 cfs will be maintained. All the above data are preliminary and <br />are subject to revision. <br /> <br />~ <br /> <br />t <br />i <br /> <br />Of concern here is the question of what will happen to the <br />.-!!LorphoJogy..--e-fth~eStream channel as a result of changes ; n streamflow <br />and sediment discharge brought about by these reservoirs. In parti- <br />cular, the following questions were posed. <br /> <br />1. What will be the meander pattern? <br />2. What will be the configuration of the channel? <br />3. What will be the substrate material, and <br />4. What will be the pool-riffle sequence? <br /> <br />Cross section data were provided for four reaches of the river. <br /> <br />1. Maybe 11 <br />2. Li ly Park. <br />3. Mantle Ranch <br />4. Box Elder <br /> <br />. <br /> <br />16 <br />