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<br />OOl~.Li~ <br /> <br />data and to be consistent with CSRCU&L. An account was taken of precipitation and runoff salvage <br />to determine net evaporation rates. The net evaporation rates were applied to the estimates of average <br />annual water-surface area to yield the values of annual reservoir evaporation. <br /> <br />Laroe Reservoir Evaporation <br /> <br />Large reservoirs have significant storage and evaporation losses. Reclamation computes daily <br />evaporation which are accumulated to monthly values. The monthly values were used for <br />computation of natural flows. Reservoir evaporation is computed by Reclamation at Navajo <br />Reservoir, Vallecito Reservoir, Lemon Reservoir and Jackson Gulch Reservoir. Daily evaporation <br />values are computed using predetermined average monthly evaporation rates which are extrapolated to <br />daily rates and multiplied by day's reservoir surface area. <br /> <br />The predetermined evaporation rates were computed using data obtained from a Class "A" <br />evaporation pan formerly installed near Vallecito Reservoir (NOAA Technical Repon NWS 34. 1982) <br />and adjusting for average precipitation. The rates are not adjusted for salvage water. Pan <br />evaporation is no longer collected at any Reclamation reservoir in basin. Evaporation rates of <br />Vallecito Reservoir were used to estimate evaporation rates for the other large reservoirs by adjusting <br />for the elevation of each reservoir. Evaporation rates were developed for Cascade Reservoir for use <br />in this study. The monthly evaporation rates are used when running hydrologic models. <br /> <br />Municipal and Industrial Depletions <br /> <br />Municipal and Industrial depletions represent water use by domestic, commercial, industrial and <br />public users both in a rural and urban settings. Domestic use is for normal residential use and for <br />watering lawn and gardens. Commercial use represents use by businesses including hotels, motels, <br />restaurants, office buildings, green houses and nurseries. Industrial use represents use by the <br />manufacturing or processing industry. Public use represents use by schools, colleges, universities, <br />government and hospital buildings. <br /> <br />Municipal and industrial annual depletions for years 1986 to 1993 were estimated based on census <br />derived population data for the State of Colorado and Utah. Annual depletions for the period 1970 to <br />1985 were obtained from Reclamations Colorado River Systems Consumptive Uses and Losses five <br />year reports. <br /> <br />Census data was obtained from the Census Bureau TIGER files for years 1985 and 1990 by <br />overlaying a HUC subbasin coverage over the Bureau of Census 1985 and 1990 TIGER files. <br />Population data was summed by HUC. Since the San Juan River Basin contains mainly residential <br />users, it was decided to use the average rate of 205 gpcd for Colorado and 245 gpcd for Utah <br />multiplied by the consumptive use factor of 0.43, as used in the Colorado River Systems Consumptive <br />Uses and Losses Report, 1981-1985. <br /> <br />The annual municipal and industrial depletions for the State of New Mexico were obtained from the <br />New Mexico State Engineers Office report on "Water Use by Categories in New Mexico Counties <br />and River Basin, and Irrigate Acreage" report for 1975, 1980, 1985 and 1990 published once every <br />five-years. Data from each five-year report was used to represent the preceding five years. <br />Depletions for 1991 to 1993 was based on the 1990 report. <br /> <br />DRAFT - SJRIP Hydrology Model Documentation <br />June 18,1999 <br /> <br />25 <br />