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<br /> <br />. <br /> <br />. <br /> <br />At present, the area of the watershed south of <br />70 consists of developed land and irrigated <br />with potential for development. The area <br />Interstate Highway is presently undeveloped. <br /> <br />Interstate <br />farm land <br />north of <br /> <br />2.2 Climate <br /> <br />The climate of the study area is classified as arid to <br />semi-arid. The average annual precipitation is 8.41 <br />inches, including an average annual snowfall of <br />. approximately 19 inches (Reference 2). <br /> <br />Elevation greatly influences the precipitation amounts <br />with the higher elevations of the Book Cliffs (headwater <br />area of Indian Wash) receiving from 10 to 20 inches. <br /> <br />. <br /> <br />Occurrence of precipitation is extremely variable with a <br />large part of the total concentrated in several months. <br />Late summer convective-type cloudburst storms of small <br />aerial extent and early-fall, general rain over large <br />areas normally make August, September and October the <br />wettest months of the year. SnOl,melt In the area is <br />light. <br /> <br />. <br /> <br />. <br /> <br />The temperature extremes at Grand Junction are evidenced <br />by mean maximums ranging from approximately 380p in <br />January to approximatelx 940p in July, and by mean <br />mInImums ranging from 150p in January to 620p in July. <br />Cooler temperatures prevail in higher mesa areas. <br /> <br />2.3 <br /> <br />Flood History <br /> <br />. <br /> <br />Historically the principal cause of flood problems on <br />Indian 11'ash has resulted from intense localized <br />thunderstorms. These storms often occur over the <br />steeply-sloped upper half of the watershed with little or <br />no precipitation being recorded in Grand Junction. The <br />precipitation intensity rises with increased elevation, <br />as does the velocity of runoff and sediment production. <br />Snowmelt flooding is negligible on Indian Wash. <br /> <br />. <br /> <br />. <br /> <br />Information [rom local residents indicate that before <br />construction of the SCS 111'1 flood retention structure, <br />damaging floods occurred on an average of every six <br />years. Precipitation records indicate that large storms <br />occured in September 1896, May 1906, October 1908, August <br />1921, August 1938, September 1941, June 1954, May 1955 <br />and June 1958. The 1908 storm produced the largest 24- <br />hour total precipitation of 2.50 inches. The 1938, 1954, <br /> <br />. <br /> <br />5 <br /> <br />. <br />