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<br />n81932 <br /> <br />Plata 100%, Mineral 25%, Montezuma 100%, Mesa 24%, San Miguel 100%, San Juan 89% and <br />Montrose 49%). <br /> <br />Table 2 shows the number of livestock type by County, and Table 3 shows a summary of the <br />estimated consumptive use for 1985-1990. <br /> <br />2.2 Stockpond <br /> <br />There are about 4,758 individual stockponds in the Dolores and San Juan River Basins. The <br />(storage) tank capacity for each stockpond was obtained from a Dbase file provided by the State <br />Engineer's Office. Individual stockpond tank capacities were summed into two aggregates <br />(stockponds located above 7750 ft. and stockponds below 7750 ft in elevation). This elevation is <br />chosen because, all stockponds located above 7750 ft. elevation use a fullness factor equal to 0.87, <br />while the rest use a factor of 0.75 (USBR, 1991). <br /> <br />Tank capacity is converted to its equivalent surface area for both aggregates by using the following <br />expression: <br /> <br />SA = !11Q4<;ro.9 <br /> <br />where SA = equivalent surface area (acres), and C = aggregate tank capacity (acre-ft). The above <br />equation is obtained from Arnold and Williams (1985). Table 4 shows the aggregate stockpond <br />capacity and surface area in each sub-basin. <br /> <br />Climate data used to determine evaporation are retrieved from monthly weather files using CROSS <br />weather stations and weights. The advantage of the aggregation is that instead of assigning a weather <br />station weight for each separate stockpond, the assignment can be made for each sub-basin consistent <br />with what is being done for the irrigation category. Unfortunately, complete evaporation data are <br />rarely available from weather stations and pan evaporation data are difficult to obtain during the <br />winter. Evaporation is then indirectly obtained from the monthly estimates of mean temperature by a <br />formula proposed by Blaney (1960) when data are unavailable: <br /> <br />e = O.7ktp1lOO <br /> <br />where t = mean monthly temperature (deg F), p = percentage monthly daylight hours, k = Blaney <br />monthly coefficients. Table 5 shows the summary of the stockpond evaporation values as calculated <br />with the CROSS CU Model. <br /> <br />2.3 Reservoir <br /> <br />Reservoir surface area and evaporation are reported by the United States Geological Survey for 1990 <br />by Hydrologic Unit, but not for 1985. Values reported for surface area and evaporation by the USGS <br />are shown in Table 6, these data can be obtained from the USGS world wide web page at <br />http://h20.er.usgs.gov/public/watuse. The program has the option of calculating evaporation based on <br />weather data if the surface areas of the reservoirs are provided. <br /> <br />2.4 Municipal <br /> <br />Population data were obtained from the 1980 census (Bureau of the Census, 1981) and 1990 census <br />(Bureau of the Census, 1991). Values for the years 1985-1989 were obtained by linear interpolation <br />for county and municipality populations. The total municipal population located in the basin (Table <br />7) was subtracted from the basin-wide population to obtain a rural population for each county. The <br /> <br />11.26.96 <br /> <br />2 <br /> <br />t2.09-13 IDS/csu <br />