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<br />I <br /> <br />I <br />I- <br /> <br />I <br /> <br />,I <br /> <br />I <br />I <br /> <br />I <br /> <br />I <br /> <br />I- <br />I <br /> <br />'I <br />II <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br />I- <br /> <br />I <br /> <br />- <br /> <br />. <br /> <br />provide the same comprehensive benefits as a large proj ect, it can provide a <br /> <br /> <br />measure of water reliability to the largest block of irrigated lands in the <br /> <br /> <br />District, the Gurley and Cone service areas. The enlargement is also <br /> <br /> <br />compatible with a larger San Miguel project and could serve as part of a <br /> <br /> <br />comprehensive storage and distribution system. <br /> <br />4.2 Irrigation Water Requirements <br /> <br />Irrigation patterns in the District have followed natural runoff patterns. <br /> <br /> <br />An over-application of water generally occurs in the early season when creek <br /> <br /> <br />water is abundant. In May and June, water application is consistently greater <br /> <br /> <br />than the potential consumptive use, constituting a surplus as far as the actual <br /> <br /> <br />crop is concerned. Prevalent theory among the irrigators is that the surplus <br /> <br /> <br />water serves to saturate the subsoil layers and thereby reduce the percolation <br /> <br /> <br />losses from water applied later in the season. There is no conclusive evidence <br /> <br /> <br />to indicate that this is so. It is possible that this over-application is <br /> <br /> <br />actually detrimental to the crop yield. But with no better storage <br /> <br /> <br />alternative, farmers apply the water when it is available. <br /> <br />Irrigation water use can be determined from ditch diversion records which <br /> <br /> <br />are maintained by the State of Colorado through the Office of the State <br /> <br /> <br />Engineer. Records for the project service area are kept in Denver at the State <br /> <br /> <br />Engineer's office and at the Irrigation Division 4 office in Montrose. <br /> <br /> <br />Measurements of flow at ditch headgates are recorded during the day-to-day <br /> <br /> <br />administration of priorities by the district water commissioner or his <br /> <br /> <br />deputies. Actual consumptive use of the applied water can only be estimated. <br /> <br /> <br />Several factors influence this consumption at any given moment including the <br /> <br /> <br />deep percolation rate, evaporation rate, transpiration rate, soil moisture, and <br /> <br /> <br />amount of water being applied. The ideal demand for land in the Project area <br /> <br />is listed in Table 4.2. <br /> <br />Years of research have produced empirically derived methods for estimating <br /> <br /> <br />the consumptive use of various crops. The Jensen:-Haise method is one such <br /> <br /> <br />method which equates readily available data such as monthly solar radiation, <br /> <br /> <br />temperature, precipitation, and crop characteristics, to produce monthly <br /> <br />estimates. The Jensen-Haise method was employed in this study to determine the <br /> <br />-11- <br />