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<br /> <br />1999 <br /> <br />Water Accounting Report to the Rio Grande Compact Commission <br /> <br />Engineer Advisers <br /> <br />SAN JUAN-CHAMA PROJECT <br /> <br />Heron Reservoir <br />Computations of the Rio Grande basin inflow to Heron Reservoir for 1999 were made <br />using the ratio method. The ratio method is the basis for determining the natural flow <br />(Rio Grande) within the Willow Creek drainage area. The daily volume was measured <br />directly using the Willow Creek gage above Heron Reservoir, and when SJ.Cdiversions <br />were in progress, the gaged flow was adjusted for Azotea Tunnel outlet gaged flow <br />less a small channel loss, The natural volume was then adjusted bycthe appropriate <br />historical correlation factor to arrive at the amount to be bypassed at Heron Dam, The <br />correlation factors were developed using the historical gage data for Willow Creek <br />above Heron Reservoir and Willow Creek at Parkview (Heron Dam);' <br /> <br />Frequency analyses of the streamflow data forWillow'Creek.atParkview between <br />1943 and, 1970 indicate that flows of 1 cubic feet per second (fe/s) were exceelllied <br />approximately 60% percent of the time: The mean annual stream flow values indicate <br />only one year in the period that averaged less than 2 ft3/s. Seepage from Heron Dam <br />averages between 2 and 3 ft3/s at; current storage levels. Thus, the base flow of <br />Willow Creek at Heron Dam (Rio Grande ,flow) approximates the seepage from the <br />dam, <br /> <br />Table 1 (page 1) illustrates the computed natural flow.at Heron Reservoir using the <br />seepage as the base flow. Table 2 (page2) computes the unaccounted gains or losses <br />on the reservoir, Gains in excess of the net evaporation volume computed for the <br />month were considered natural gains and subsequently delivered as Rio Grande water. <br />Table 3 (page 3) illustrates actual operations of Heron Reservoir for 1999, Column 5 <br />is a balance between the end of month contents using the operational inflow and <br />outflow data. Table 4 (page 4) lists SJ-C water delivered for each contractor from <br />Heron Reservoir in 1999. <br /> <br />Tunnel invert, siphon, and channel work was suspended at the beginning of 1998 and <br />resumed in the winter of 1998/1999, Diversionsbegan on March 5, continued most <br />of the year as water was available through, and ended on September 24, Total <br />amount diverted was 118, 901 AF, This amount is 22, 860 AF above the running 10- <br />