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<br />. .' <br /> <br />O~11!O <br /> <br />..viii- <br /> <br />and in the offioe by Leslie C. Pampel. R. Evan Kennedy, and others. Robert <br />1. lowry. Jr., research engineer for the U. S. Reolamation Bureau, parti- <br />cipated in planning the invastigations. and with Engineer ArtlnJ.r F. Jom- <br />son, in analyzing the data oompiled during the first two seasons. Through- <br />out the study period valuable assistance was rendered by Bureau engineers <br />D. J. Paul and N. B. Platt. The Unoompahgre Water Users' Assooiation 00- <br />operated in the field'work through Jesse N. Thompson. superintendent. and <br />John B. Tobin. hydrographer. Valuable assistanoe was rendered by Fred S. <br />Hotchkiss, Division Engineer, Irrigation Division No.4, State of Colo- <br />rado. <br /> <br />As desoribed in detail in Part I of the report. the drainage <br />basin of the Uncompahgre Ri ver embraces an area of 1,110 square miles. <br />ranging in elevation above sea-level from 4,900 feet at the rivers mouth <br />near Delta, to more than 14,000 feet at the orests of mountain peaks in <br />its headwater souroes above Ouray. Beoause of widely varying physioal. <br />climatio and other oondi tions, the basin has been sub-divided into three <br />seotions. The first or upper section. above Ouray, is entirely mountain- <br />ous and extremely preoipitous. Elevations are too high and temperatures <br />too low for agricultural operations other than summer grazing of live- <br />stook. Preoipitation at the hiGher elevations amounts to 30 inches or <br />more annually. largely in the form of snow. Henoe section one consti- <br />tutes the prinoipal souroe of water supplies for valley lands below. dur- <br />ing the period of several ""eJ:s in late spring or early sUllllll8r when the <br />aooumulated snow is melting rapidly. <br /> <br />ThB second or middle seotion of the river, from Ouray to Colona, <br />is charaoterized by narrow valleys surrounded and sheltered by nearby <br />mountains, foothills and plateaus. - lands suitable for irrigation being <br />limited in extent. Although irrigation was first undertaken in the basin <br />in the middle section. from about 1875 to the present time only about <br />15,000 acres have been brought under irrigation. which lands are used <br />chiefly for the production of hay in conjunction with livastock operations. <br />Because of the limited extent and scattered locations of the irrigated <br />areas in the middle section. they are excluded from the detailed investi- <br />gations hBrein reported. <br /> <br />In the third or lower section frem Colona to Delta, the valley <br />is wider and less sheltered by surrounding mountains. plateaus or mesas. <br />The climate, though favorable to growing diversified crops, is typioal- <br />ly arid. Normal precipitation averages but 9 inches annually. The <br />practios of irrigation in the lower seotion began in the 1880's. At the <br />turn of the oentury a total of about 30.000 acreS had heen brought under <br />irrigation, which represented the lilnits of de'velopment based on unregu- <br />lated local water supplies. Although larger areas of apparently suit- <br />able lands were available. and although total basin runoff averaged <br />275,000 A.F. annually. of which 250,000 A.F, arrived at the lower section <br />in the average ,year. irrigation was limited to 45,000 acres in the basin. <br />and to 30.000 aores in the lover section. by the nature rather than the <br />total llJIlounts of ti18 streamfloYm and water' supplies. which were adequately <br />