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<br />FEB-07-1997 11:08 <br /> <br />002173 <br /> <br />DEPT OF NATURAL RESOURCES <br /> <br />1 303 866 4058 P.06/14 <br /> <br />rr~"",;nQ"': SlIbjcCllo R("vlsion <br /> <br />OCloMr 24. /995 <br /> <br />Orchard Mesa Check Case <br />Analysis of Irrigation Consumptive Use <br /> <br />Background <br /> <br />Releases are made from the Green Mountain Reservoir 66,000 acre foot Historic Users Pool (HUP) <br />to supply iITigation and domestic water appropriations when the flow of the Colorado River and its <br />tributaries is not sufficient to satisfy these water rights. Beneficiaries of the HUP are those water <br />rights perfected by use on or before October IS, 1977. <br /> <br />A reservoir drawdown curve (rule curve) is being developed to aid in managing releases from the <br />HUP, One criteria of the rule curve is to ensure sufficient quantity of storage water exists during the <br />irrigation season to meet the replacement needs ofHUP beneficiaries junior to the Shoshone water <br />right. This analysis was conducted to quantify irrigation consumptive use by this group of HUP <br />beneficiaries. Municipal consumptive use is not addressed in this analysis, <br /> <br />Method <br /> <br />Daily diversion records and water rights records compiled by the State of Colorado, Division of <br />Water Resources, Water Division Five served as the base data for the analysis_ Consumptive use <br />calculations were made using the modified Blaney-Criddle method, as described in Technical Release <br />Number 21 (TR2I), Irrlgatioll Water Requirements, published by the US Department of <br />Agriculture, Soil Conservation Service. The Blaney-Criddle method was originally developed for <br />estimating seasonal consumptive use; it was found that the seasonal crop coefficients were not <br />constant for short time periods (30 days or less). Two modifications to improve the accuracy of the <br />Blaney-Criddle method when estimating short-period consumptive use 'are described in TR21; these <br />relate to use of climatic and crop growth stage coefficients. <br /> <br />Computer programs and databases supporting the modified Blaney-Criddle consumptive use <br />calculations had previously been developed by the State, The State's Water Division 5 provided the <br />Bureau of Reclamation with copies ofth~ programs and data, and assisted with installing and testing <br />the programs on Reclamation's computers. <br /> <br />ReclamatiDn made the following modifications to the State's programs and data: <br /> <br />I. Added November data to the data tables for air temperature, crop coefficients, and daylight <br />hours. This was necessary to calculate consumptive use after October 14. <br />2. Added program logic to support multiple-day program runs; approximately 200 single-day <br />program runs were required for the analysis. <br /> <br />. For s~tlJ~mt1J1 purposes 01l{\' . <br />