WSP03538 - Laserfiche WebLink

Home Browse Search

U00171 . in sands, gravels and decomposed granite. An estimated 2 million acre-feet of irrigation water is lost through seepage processes in Colorado each year. Seepage from canals and reservoirs not only reduces the availability of water to the operating company, but also (1) adds to the salt buildup in the soil profile and ground-water reservoirs, (2) sustains high-water- table areas and encourages the growth of phreatophytic vegetation and (3) reduces the area of land for agricultural use. On the other hand, seepage may be beneficial in that it recharges the underlying ground-water reservoir. . Depending on the cost and effort analyses of lining a specific canal or reservoir, various materials may be incorporated. Linings currently utilized in Colorado include (1) bentonite (or clay); (2) compacted earth; (3) both reinforced and unreinforced concrete; (4) asphalt, rubber and plastic membranes; and (5) chemical treatments, Operational losses Operational losses are defined as that water loss resulting from the manner in which the reservoir and/or canal system is operated. This loss includes overflow or breakage of canal banks, waste at the end of the main canal'or lateral system, leakage past gates and other control structures, and direct dumpage back to the river system. In order to supply the most downstream lateral along a given canal, some overflow at the downstream end is often required. Direct dump back to the river system may be neces- sary during periods of unusually high precipitation or unanticipated can- celing of a headgate diversion. In some instances such operational losses may be required to flush out excessive sediment loads or to satisfy down- stream calls on the river. It should be mentioned that seepage losses and operational losses which tend to reduce the efficiency of one canal and reservoir system may contribute to the water supply and thereby bolster the efficiency of one or more lower canal systems. . -14-