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<br />0':> <br />co <br />C'? <br /> <br />Irrigation Requirements and Water Supplies <br /> <br />Sources of Data <br /> <br />Reports on several studies include estimates of irrigation requirements in <br />the general vicinity of the Silt project, Included are the following: <br />(1) Appendix B of the Record of the Upper Colorado River Basin Compact Com= <br />mission; (2) Consumptive Use of Water in the Irrigated Areas of the Upper <br />Colorado River Basin, by Blaney and Criddle; and (3) Consumptive Use and <br />Irrigation Water Requirements of Crops in Colorado, by Blaney and Criddle, <br />Additional related information is contained in the Water Supply Papers of <br />the U, S. Geological Survey, Climatological Data by the U, S, Weather <br />Bureau, Colorado Heat and Moisture Indexes for Use in Land Capab ility Clas- <br />sification by the Soil Conservation Service, and other publications, These <br />and other available related reports were carefully reviewed for the purpose <br />of this study. In addition, informatI-.:"l was supplied by technicians of the <br />Colorado State University, Colorado Agricultural Experiment station, Colorado <br />Cooperative Extension Service, Colorado State Engineer, Agricultural Research <br />Service, U. 5, Bureau of Reclamation, U, S. Soil Conservation Service, and <br />othe rs fam il i ar wi th the area, <br /> <br />Water Requirements <br /> <br />Consumptive use requirements for the principal crops in the area were esti- <br />mated by the Blaney...criddle procedures (table 4). Long climatological <br />records are available for the town of Rifle, located adjacent to the project <br />area; however, there are material differences in elevation between Rifle <br />and the several parts of the project, Some adjustment of both the teapera- <br />ture and precipitation records at Rifle is necessary, therefore, before they <br />can be considered representative of the project area, There are no data <br />available to guide estimates of the amount of adjustment needed, In addi- <br />tion, considerable variation of elevation occurs within the various parts <br />of the project area, Considering these limitation, a refined and detailed <br />estimate of consumptive use within the project area was not atteapted. <br />From inspection of the area and discussions with technicians familiar with <br />the area, it appears that the Davie Mesa-Harvey Mesa area could be reasonably <br />considered as one unit for purposes of estimating the consumptive use re= <br />quirements, and the Dry Elk Valley as a separate unit, <br /> <br />Estimates of mean temperatures for the two project areas described above <br />were made by application of standard adiabatic lapse rates, 30 per 1,000 <br />feet, for the elevational differences, to the average mean temperature at <br />Rifle as given by the U. 5, Weather Bu~au, Bulletin W, Supplement ll~ <br />(1931-1952). <br /> <br />For the purpose of this study, effective precipitation is considered to <br />be 85% of the average precipitation for the ten driest consecutive years <br />(1931-1940). Extension of the precipitation record at Rifle to the project <br />area was difficul t in the absence of data on the variability within the <br />area. The Dry Elk Valley presents considerable uncertainty, as it is <br />reputed to be at least partially in an area of "rain shadow" north and east <br />of the Grand Hogback, <br /> <br />- 14 - <br />