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<br />ONFARM SALINITY CONTROL INI/ESTlGATIONS <br />FOR <br />THE GRAND VALLEY AREA <br />State of Colorado <br /> <br />Plan of Work Outline <br />January 1975 <br /> <br />Description of Basin <br /> <br />Physical - The Grand Valley area (Grand Valley Subbasin in the Type IV <br />River Basin Report) of Colorado lies at the junction of the Gunnison <br />River with the Colorado River. The area was opened to settlement in <br />1881. The Grand Valley Irrigation Company, started in 1882, diverted <br />water from the Colorado River near the present site of Palisade to <br />irrigate 22,500 acres. From 1889 to 1907, five other small irrigation <br />districts were formed to divert water from the Colorado River to irri- <br />gate from a few hundred to a few thousand acres. The last major irri- <br />gation development in the Valley was the U.S. Bureau of Reclamation <br />Grand Valley Project started in 1"912 to irrigate about 42,000 acres. <br />Prior to settlement and the development of irrigation, the Valley was <br />described in many reports as very barren with only a sparse cover of <br />greasewood, sagebrush and desert shrubs. <br /> <br />The mean annual temperature at Grand Junction is 520 F. and ranges from <br />a July mean of' 780 F. to a January mean of 260 F. The annual precipi- <br />tation averages only 8.29 inches and is rather uniformly distributed <br />throughout the year. The elevation at Grand Junction is around 4,850 <br />feet above sea level. The average growing season is 190 days. <br /> <br />There are about 80,000 acres of irrigated land in the Valley, of which <br />about 11 percent is not cropped in anyone year. The principal crops <br />grown in order of acreage are hay and pasture, corn, fruits, small <br />grain, and sugar beets. The average farm size is 50 acres with some as <br />large as 500 acres. <br /> <br />The soils of this general area are derived from the Mancos Shale For- <br />mation. This marine formation has a very high salt content and ground <br />water percolating over and through the shale picks up high concentra- <br />tions of salt which are transported to the Colorado River through waste- <br />ways, ditches, or by natural ground water movement to the river. Because <br />of the arid cl imate, these salts have not been leached naturally, and <br />high quantities remain. Lenses of white crystall ine salts are often <br />exposed during excavation operations. The Mancos Formation consists of <br />4,000 feet of relatively uniform silty clay shale with veinlets of <br />gypsum, calcite, and sodium sulphate. <br /> <br />1639 <br />