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T H E W A T E R S H E D I N B R I E F <br />The Trinchera Irrigation Company Watershed is located in the <br />southeast corner of the San Luis Valley. The watershed occupies <br />about 42,240 acres or 66 square miles in Costilla County within the <br />Mount Blanca Soil Conservation District. Trinchera Creek and its <br />tributaries flow in a southwesterly direction from the Sangre de <br />Cristo Range to its confluence with the Rio Grande near La Sauses. <br />Trinchera Watershed is transected by U. S. Highway 160, State <br />Highways 10 and 159, and the. Denver and Rio Grande Western Railroad. <br />There are two unincorporated towns within the watershed, Blanca <br />and Fort Garland. Blanca had a population of 212 per 1970 census. <br />The watershed is about 15 miles long in a southwest - northeast <br />direction and about 10 miles wide at its widest point. The irrigated <br />land is nearly level to gently sloping topography. E16vations range <br />from 7,900 feet at the gaging station on Sangre de Cristo Creek east <br />of Fort Garland to 7,640 feet below Smith Reservoir. , <br />The irrigated portion of the watershed has an arid (desert) climate. <br />Its precipitation and elevation is similar to that of Manassa located <br />to the southwest of the watershed in Conejos County. ManasSa's average <br />annual precipitation is 6.76 inches, 54 years of record, and elevation <br />is 7,681 feet. Seventy -eight percent of the precipitation occurs between <br />the months of April through October. <br />Three distinctive soil associations comprise the irrigated land. <br />The eastern 40 percent has deep, nearly level to gently sloping, well. - <br />drained loamy soils. The central 30 percent has medium depth and deep, <br />nearly level, poorly drained loamy soils that are moderately to severely <br />saline. The western 30 percent has medium depth and deep, nearly level <br />to gently sloping, excessively drained, sandy soils. <br />Present land use in the watershed is as follows :.28 percent irri- <br />gated cropland, 65 percent rangeland, and 7 percent other uses. <br />There are about 94 landowners and 54 operating units in the watershed. <br />Agriculture is characterized by the production of vegetable crops, malting <br />and feed barley, and alfalfa. There are two grading and packing plants <br />located at Blanca, one for cabbage, lettuce and carrots and one for <br />potatoes. <br />