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<br />L'" <br />!'- <br /><:.D <br />Q <br />o The average seepage rate (Table 4), for the Stage One area is 0.28 foot <br /> <br />,..-, <br />'--' <br /> <br />per day (l,900 acre-feet per year) for canals and 0.62 foot per day for <br /> <br />laterals (4,000 acre-feet per year). For Stage One and Reed Wash study <br /> <br />areas, lateral ponding test results were used rather than inflow-outflow <br /> <br />measurements. variation of materials, length of reach, and sediment trans- <br /> <br />port phenomenon may all contribute to discrepancies in the t,.o methods. The <br /> <br />seepage values chosen were supported by water budgets of the ground-water <br /> <br />system, particularly the volume of drain baseflow compared to the inflow to <br /> <br />the ground-water system (see data presented under salt and wster budget <br /> <br />discussions). <br /> <br />Infiltration <br /> <br />During the 1975 growing season, the Agricultural ResearGh Service (ARS) <br /> <br />(Alleviation of Salt Load in Irrigation Water Return Flow of the Upper <br /> <br />Colorado River Basin, Agricultural Research Service, Septemb,er, 1977) <br /> <br />conducted furrow irrigation studies in Grand Valley. During the study, 13 <br /> <br />sites were monitored with 8 different soil types in combination with short <br /> <br />(300 to 650 feet) and long irrigation runs (650 to 1,300 feet). At least <br /> <br />every other irrigation was monitored for advance of stream, water intake <br /> <br />rate, and chemical quality, plus sediment content of tailwater runoff. The <br /> <br />sites consisted of a four-row test plot to which the farmer applied water in <br /> <br />the same manner as the rest of the field. Inflow to the plot was measured <br /> <br />with an orifice box, and the outflow was measured with a Trspezoidal flume. <br /> <br />The 12 hour intake rate as measured by ARS of the various soil types varied <br /> <br />from about 0.10 to 0.39 inch per hour with an average of about 0.10 to 0.13 <br /> <br />inch per hour. <br /> <br />14 <br />