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Watershed Resources The climate is classed as semiarid. Average annual precipitation at Sedgwick is 17.01 inches. Periods of low rainfall are common with an uneven distribution of precipitation from year-to-year. The principal source of precipitation that causes damaging floodwater and sediment runoff is from high-intensity, short duration convection-type thunder- storms occurring over rather limited areas, normally in the period from April to October. The greatest 24-hour amount of precipitation recorded at the Weather Bureau station 5 miles south of Sedgwick was 5.00 inches on May 5, 1969, A number of amounts in excess of 5.00 inches were reported in farm gages throughout the watershed in 1965 and 1968. Temperature has ranged from a low of -400 F. to a high of 1100F. with an average annual temperature of 500F. The average frost-free growing season is 143 days based on 56 years of Weather Bureau records at Julesburg, Colorado. Altitudes range from about 4,150 feet at the northwestern edge of the watershed to 3,510 feet at the southeastern edge of the watershed 'near Ovid, Colorado. Geologic formations exposed withi~ the watershed consist of rocks and ,', _ ,sediments of Tert.ian'-amLQ\!ateJ':~ages., Rpnroc!<-oceu++-i-ng-at--{}F-l'lear 'the surface at the' lower ends of ,.the 'tributary drainages consists pre- dominantly of blocky claystone and siltstone of the Brule formation of Tertiary age. In the upper part of the watershed, these rocks are overlain by the Ogallala formation of Tertiary age, which consists of beds of stream-deposited gravel, ~and, silt, and clay. Some of the sand and gravel of, the Ogallala is cemented by calcium carbonate, which forms, a rock ranging from a soft friable sandstone to a relatively hard sand- stone. " Much of the middle part of the watershed is underlain by Pleistocene terrace deposits consisting of alluvial sands, silts and clays. Through- out most of the upper and middle portions of the watershed, the surface is mantled with wind-deposited silt and clay or silt and fine sand of Pleistocene age. The alluvial plain in the lower part of the watershed is underlain by stream-deposited ~ilt, clay and sand of Pleistocene and Recent Ages. Soils of the watershed are mainly deep or moderately deep loams or sandy loams. In the nonirrigated cropland area in the upper watershed, the soils on slopes 'below nine percent are higb"lProducing wheatland, and the land now in cultivation has lost little surface soil. Steeper lands are mostly in native grass. Cover is such that there are no areas of critical erosion or sediment production. 7