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<br />Climate <br /> <br />The mean annual temperature for Lower Gunnison stations is 49.60 F. and <br />35.40 F. for Upper Gunnison stations. The normal precipitation for four <br />lower Gunnison weather stations is 9.75 inches and 17.61 for three upper <br />basin stations. The report by lorns and Others (1965) indicates areas <br />of greater than 40-inch precipitation for all higher mountain areas on <br />the north, east and south boundaries of the basin. <br /> <br />Because of the arid cl imate in the valley, salts have not been leached <br />naturally and high quantities remain. Lenses of white crystal! ine salts <br />are often exposed during excavation operations. <br /> <br />Soi 1 s <br /> <br />Most of the soils and subsoils of the Lower Gunnison Valley are derived <br />from the Mancos shale formation which underlies the entire valley. InlS <br />marine shale formation has a very high salt content and ground water <br />percolating through the shale picks up high concentrations of salt which <br />are transported to the Gunnison River by wasteways, ditches or natural <br />ground water movement to the river. The thickness of the Mancos salt- <br />bearing formation ranges from 3,000 to 5,000 feet. A National Soi I <br />Survey covers the irrigated land, providing a data base for conservation <br />farm planning. The soils derived from the Mancos shale are high in clay <br />and silt content, slowly permeable, high in soluble salts, very suscep- <br />tible to sheet and gully erosion and require careful management. <br /> <br />Water Resources <br /> <br />The water resources of any watershed are a combination of the precIpI- <br />tation, by type and timing, plus surface streamflow, ground water and <br />lakes. Han-made reservoir storage and trans-basin water movement improve <br />timing and total suppl ies available for use. The quantity and qual ity <br />of stream outflow has also become of special interest to downstream <br />water users, and more recently, the subject of interstate regulation and <br />control. Prel iminary evaluations conducted for this study indicate the <br />average annual 1941-73 water resource for the Gunnison River Basin to be <br />as follows: <br /> <br /> 1941-73 Estimated <br /> Drainage Annual Undepleted Consumptive 1941-73 <br />Location Area Yield Supply Use Outflow <br /> (sq .mi.) ( in.) (ac.ft.) (ac.ft.) -(ac.ft.) <br />. Upper Gunnison 3,952.6 5.9 1,238,500 58,500 1 , 180,000 <br />Lower Gunn i son 3,148.3 4.9 827,000 366,000 461 ,000 <br />Whitewater 919.1 2.5 106,500 20,500 86,000 <br />TOTAL GUNNISON <br />RIVER 8,020.0 5.1 2, 1 72 , 000 445,000 1,727,000 <br /> ~77 <br /> 3 <br />