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<br />~~) <br />"'.::J" <br />o <br />...... <br /> <br />2 <br /> <br />(:~ <br /> <br />canals are earthlined. About one-fourth of the irrigated lands have <br />been leveled or smoothed to impz-ove surface application of irrigated <br />water. The water disposal systems include 14 natural washes and some <br />manmade community or group drains. Most of the surface return flow <br />finds its way into the natural washes before returning to the Colorado <br />River. <br /> <br />In past time, the Colorado River has eroded a deep wice channel through <br />the Mancos Shale Formation which has since been refilled with alluvial <br />materials to a depth of some 50 to 60 feet. The present channel of the <br />Colorado River is incised in the alluvial materials which are more per- <br />meable than the shale, and serve as a general acquifer for the flood <br />plain area. This acquifer is recharged by deep percolation losses from <br />irrigation, canal seepage, and in the watershed portion of the Grand <br />Valley area. In some places, the acquifer is under artesian pressure. <br />The salinity of the water in the acquifer varies from 6,000 to 36,000 <br />parts per million of total dissolved salts. Salinity concentrations <br />normally increase with depth. <br /> <br />The upland drainage or diffuse salt source area is the drainage above <br />the Grand Valley irrigated area. The study area encompasses some <br />839,000 acres. Annual precipitation varies from about eight inches <br />in the lower valley to 20 inches on a small portion in the northwest <br />portion of the basin. <br /> <br />Economic - Agricultural income from the sale of farm products in this <br />subbasin amounts to about 40 percent of the total for the basin. The <br />subbasin contains about 65 percent of the irrigated cropland in Mesa <br />County, but the value of farm product sales amounts to about 75 percent <br />of the total for the county. <br /> <br />In 1969 there were about 1,125 farm or ranch operating llnits. Of the <br />1,125 farms 26 percent had incomes of over $10,000; 31 percen+, had <br />incomes between $2,500 and $9,999; and 44 percent had incomes of less <br />than $2,500. However, of the 44 percent with less than $2,500 incomes <br />only five percent are fUll-time farmers under 65 years of age. The <br />remaining 39 percent are either part-time or part-retirement farmers. <br /> <br />Market value from the sale of all agricultural products in 1969 was over <br />$13 millions, of which 65 percent is from the sale of livestock, poultry, <br />and their products, and 13 percent is from the sale of peaches, apples, <br />pears, and cherries. Other income comes from the sale of hay, grains, <br />vegetables, and nursery products. <br /> <br />According to the 1969 Census of Agriculture, hay averaged 31 percent, <br />corn 14 percent, improved pasture 17 percent, other fieli crops 7 per- <br />cent, and sugar beets one percent of the irrigated area. In 1964, hay <br />irrigated was 29 percent, corn 11 percent, improved pasture 23 percent, <br />