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<br />. <br /> <br />The climate at Rio Grande Reservoir is typical of other Colorado <br /> <br /> <br />mountainous areas at 9400 feet elevation. Summers are cool, with <br /> <br /> <br />occasional afternoon showers. Winters are long and severe. The <br /> <br /> <br />average monthly precipitation and temperatures are listed in Table 1 <br /> <br /> <br />based on four years of available climatological data. The average <br /> <br /> <br />snow moisture content at the Upper Rio Grande snow course is also <br /> <br /> <br />presented in the table. <br /> <br />Historic Reservoir Inflow <br />Rio Grande Reservoir is located near the headwaters of the Rio <br />Grande. The drainage basin above the dam is 162 square miles in <br />area. The watershed elevation varies from 9450 feet at the reservoir <br />to over 13,000 feet along the Continental Divide. River flow is <br />primarily dependent on snowmelt runoff in May through July, with <br />additional flow provided by rainstorms and continuous groundwater <br />percolation. The average monthly river inflow at the reservoir for <br />the period of 1969 through 1980 is presented below. <br /> <br />.' <br /> <br /> (Values in cubic feet per second) <br />January 27 July 361 <br />February 28 August 114 <br />March 33 September 96 <br />Apri I 94 October 61 <br />May 507 November 46 <br />June 834 December 32 <br /> <br />The flow duration curve at the reservoir is presented as Figure 4. <br />The maximum monthly average streamflow for the period of 1950 through <br />1980 was approximately 1,400 cfs in June, 1979. The minimum monthly <br />flow was about five to ten cfs in January, 1977. The maximum spill- <br />way and outlet works release was about 7.500 cfs in 1927. <br />There are no gaging stations upstream of Rio Grande Reservoir <br />and no records of reservoir inflow. The United States Geological <br />Survey has maintained a gaging station since 1909 at a point on the <br /> <br />. <br /> <br />-13- <br />