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<br />County <br /> <br />1970 <br /> <br />1980 <br /> <br />1990 <br /> <br />2000 <br /> <br />Delta <br />Montrose <br />Ouray <br /> <br />15,290 <br />18.370 <br />1.550 <br /> <br />17.500 <br />18,800 <br />2,100 <br /> <br />20,600 <br />20,800 <br />2,700 <br /> <br />24,200 <br />23,700 <br />3.200 <br /> <br />About 42 percent of the area is in private ownership. The significance <br />of 58% of the drainage area being in federal ownership is readily <br />apparent when considering the need for a cooperative watershed treatment <br />program. Much of the highly erodible land is managed by the BLM. Most <br />of the 36 percent of the Lower Gunnison area managed by the U.S. Forest <br />Service is in the high elevations and is a low producer of salt and <br />sediment. <br /> <br />The irrigation systems in the study area are constantly undergoing <br />change. Owners of the higher capabil ity lands are install ing concrete <br />ditches, underground pipel ines or using gated pipe directly out of a <br />dirt ditch. However. a -majority of the land is still being irrigated <br />directly out of earth ditches using the turnout, set ditch method. <br />There are no successful border or sprinkler systems in the study area. <br /> <br />Except for the high mountain meadows, irrigation water is appl ied to the <br />field by turning it into corrugations or furrows. <br /> <br />I I I. PROBLEMS AND NEEDS <br /> <br />Sal inity Problems <br /> <br />'7 <br />b <br /> <br />The problems with sal inity on irrigated cropland are generally related <br />to poor drainage, and sizeable areas of formerly irrigated cropland in <br />the Lower Uncompahgre Subbasin have been abandoned. There are few cases <br />of harmful salinity accumulation on irrigated lands with good drainage, <br />because the irrigation water is generally of high qual ity and most <br />fields are irrigated in excess of consumptive use requirements. How- <br />ever, the irrigation return flows from areas underlain by Mancos shale <br />contain large quantities of total dissolved solids and seriously degrade <br />the qual ity of water returning to the Colorado River system. The <br />Gunnison River discharges 1.4 million tons of salt annually. About 0.6 <br />'mi 11 ion tons are estimated to be the normal inflow and 0.8 mi 11 ion tons <br />are estimated to be related to man's activities. Most of this is caused <br />by the irrigation of 184.700 acres in the Lower Gunnison Unit. The <br />average increase in salt loading is over four tons per acre irrigated <br />per year. <br /> <br />003079 <br /> <br />5 <br />