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<br />i 73,1 large as 500 acres. I'Iark0t CiaJ.ue of farm products in 1970 vias over <br />$15 mj.llion, of which 60 p8rcent is from the sale of livestock, <br />poultry and their products and 13 percent is from the sale of peaches, <br />apples, pears and cherries. <br /> <br />. <br /> <br />The soils of this general area are derived from Nancos Shale. <br />This formation is about 4,000 feet thick, and consists of relatively <br />uniform silty clay shale vnth veinlets of gypsum, calcite and sodium <br />sulphate. This marine formation has a very high salt content. <br />Ground1rwter percolating over and through the weathered and cracked <br />upper zone of the shale picI;s up high concentrations of salt which <br />are transported to the Colorado River through wasteways, ditches, <br />or by fiatural groundwater movement to the river. <br /> <br />Return flows from the irrigated area to the Colorado River <br />probably contain as much salt now as they did at the inception of <br />irrigation. It can be assumed this level will continue unless <br />excess groundwater which dissolves salt from the Mancos shale is <br />reduced and controlled. Some of the major washes traversing the <br />irrigated area and discharging into the river have flows with <br />salinity levels in excess of 6,000 parts per million (ppm) of total <br />dissolved solids. <br /> <br />In flowing through the valley, the Colorado River salt load is <br />increased by a total of about 700,000 tons per year, with return <br />flows from irrigated agriculture in Grand Valley estimated to <br />contrib'lte about 500,000 tons of the total. Reduction of the salt <br />contribution by irrigated agriculture in Grand Valley would be <br />achieved by reducing the amount of deep percolation of applied <br />agricultural water and the leclcage from the conveyance and distri- <br />bution systems. <br /> <br />One of the measures required to reduce deep percolaticn from <br />irrigated lands is the delivery to the farms of only that Quantitv <br />of water needed to replace the moisture deficiency in tr.e farm'G . <br />soil plus the leaching requirement. This quantity is determined by <br />a Bureau of Reclamation program called Irrigation Schedulin~. This <br />program is currently being applied to 7,200 acres, or 10 percent of: <br />the Grand Valley irrigated area. It involves the computerized <br />scheduling of times and amounts of water to be applied to each <br />imlLvicJ.ual farm based on analyses of Goil moisture deficien"ies, <br />clilTI:Jtic information, crop, and other relevant data. ThrcuGh prop8r <br />irr~.ga~,j_on scheduling and changes in on-farm water delivery facili- <br />tip.s to enl".ble no more than the required amounts of "later to 03 <br />applied to the fields, reductions in deep percolation of applied <br />vrater into the underground can be achieved. Department of Agriculture <br />pl"ograms should be of assistance in improving conditions of irrigated <br />lands and facilities for irrigation. Farmers employing these <br />management practices should realize some increase in crop yield. <br /> <br />Most of the canals and laterals in Grand Valley are unlined and <br />there arG large seepage losses from these conveyance facilities, and <br />from op~n drains, to the underground. Canals and laterals serving <br /> <br />- 16 - <br />