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by distinct colluvial sediments or by the slope outwash from <br />higher elevations. The slope outwash has a character very <br />similar to pediment deposits; it is different on both sides <br />of the North Fork river, with predominantly fine-grained <br />material on the south side and coarse-grained material on the <br />north side. <br />Extensive and distinct early Pleistocene or late Ter- <br />tiary river terraces are found on the north valley side high <br />above the present North Fork channel. <br />3.3 HYDROLOGY <br />The study area lies within a region of generally dry <br />climate. Irrigation is used on most of the agricultural land. <br />All but major streams in the area are of intermittent or <br />ephemeral character. <br />3.3.1 NORTH FORK OF THE GUNNISON RIVER <br />I • <br />The North Fork of the Gunnison River, a perennial stream, <br />is the main stream in the study area. Its drainage area at <br />Paonia, immediately downstream of Stevens Gulch, is approxi- <br />mately 745 sq. miles. The nearest U.S.G.S. gaging station to <br />the study area is located 1.5 miles east of Somerset, approxi- <br />mately 9.5 miles upstream from Stevens Gulch. At this point, <br />the North Fork drains an area of 531 sq. miles. Average dis- <br />charge at this gaging station during its 47 years of records <br />is 437 cu ft/sec. The flow in the river is high during the <br />snowmelt (May - June) and low during late summer, fall and <br />winter. The natural flow of the stream below Somerset is af- <br />fected by numerous diversions for irrigation. The main di- <br />version ditches in the study area are the Fire Mountain canal <br />_ 7 _ <br />cso-irroco ca+wmr~c, wc. <br />