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<br />FEB-07-1997 11:09 <br /> <br />DEPT OF NATURAL RESOURCES <br /> <br />1 303 866 4058 P.07/14 <br /> <br />0021 H <br /> <br />PrdinrillfJry: SubjUllO R~\'i."iOIl <br /> <br />Oe/ob" 24. 1995 <br /> <br />Daylight Hours <br />The monthly percentage of daytime hours of the year for latitudes 39'. 40', and 410 north of the <br />equator were obtained from TR2I, Table I. Daylight hours for the actual latitude of each district <br />were interpolated from the daylight hours table (e.g., value for District 36 at latitude 39.6' would be <br />cDrnputed from the table values for latitudes 39' and 400). <br /> <br />Air Temperature <br />Mean monthly air temperature for a location central to each district was obtained from temperature <br />summaries prepared by the Colorado Climate Center, Department of Atmospheric Science, Colorado <br />State University. Period of record for the temperature summaries was 40 years for all locations <br />except Dillon (District 36), which had a 79-year record. <br /> <br />Consumptive Use Calculations <br /> <br />Consumptive use rate was calculated for the 15th day of the selected month, using values for mean <br />monthly air temperature, crop growth stage coefficient, and daylight hours from the data tables. <br />Consumptive use rate for the previDus or subsequent month was also calculated, depending on the <br />date selected for analysis. Linear interpolation was then used to calculate the consumptive use rate <br />for the selected date and applied to the diversion records for that date. The calculations limited <br />irrigation efficiency to a maximum of 50% (e.g.. consumptive use volume could not exceed 50% of <br />the total volume diverted). <br /> <br />Several factors that can influence consumptive use rates were not evaluated in this analysis. These <br />include effective precipitation, soil moisture holding capacity, carryover soil moisture from winter <br />precipitation, ground water contribution, and field application efficiencies (evaporation, deep <br />percolation, and surface nmofl) Applying additional factors to the computations would require data <br />collection and programming effort with no certainty of a substantial effect on the analysis results. <br /> <br />Program Output <br /> <br />Output from a single-day run of the consumptive use program consists of six tables (one for each <br />water district). The tables list each structure which diverted irrigation water on that date, with <br />columns for diversions senior to and diversions junior to the Shoshone call, acres irrigated (by both <br />senior and junior rights), total consumptive use (by both senior and junior rights), and consumptive <br />use junior to Shoshone. The six district totals for consumptive use junior to Shoshone were then <br />summed to obtain the total volume for that date. <br /> <br />Program runs to calculate daily consumptive use volume by district were made for the ] st, 8th, 15th, <br />and 22nd of each month, approximating a weekly time step'. . "Weekly" consumptive use volume was <br />calculated from the daily totals, using the following formula <br /> <br />- For st!lIlemenl purposes only .. <br /> <br />3 <br />