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2.2 LOCATION AND TOPOGRAPHY I The Gunnison River Basin is located in West-Central Colorado. Its boundary encompasses an area of 8020 square miles and includes all or major portions of Gunnison, Montrose, Delta and Ouray Counties and portions of Mesa, Hinsdale, Saguache and San Juan Counties. It is approximately 145 miles long east to west and 95 miles wide at its widest point north to south. The Gunnison River and its tributaries drain about eight percent of the area of the State of Colorado. The Gunnison River Basin ranges in elevation from approximately 4550 to 14,300 feet and has an extremely variable topography. The lower river basin has broad, nearly level to moderately sloping valleys, flanked by low rolling hills which break rather abruptly into moderately to steeply sloping mesas highly dissected by steep sided drainageways or canyons. Above the mesas on the northeast and south are steeply sloping dissected plateaus which extend to the headwaters of the major ,streams. The streams are shallow at this elevation and topography is. characterized by gently to strongly sloping valleys. These valleys are interspersed with steeply sloping smooth rolling hills at the north boundary of the Basin and very steep rough glaciated peaks on the south boundary. The upper portion of the Gunnison River Basin is typified by very high, gl aciated peaks whose slopes descend into gently to strongly sl opi ng high mountain basins and into long steep sided ridges. They are separated by strongly sloping, narrow valleys that become less steep and considerably wider at the confluence of major streams and at lower elevations. 2.3 CLIMATE Climate in the Gunnison River Basin varies considerably but generally could be considered as semiarid. Variation is due largely to the wide range in elevations. Average annual precipitation varies from more than 40 inches in the upper reaches of the basin to less than 10 inches in the lower valleys. o ; . 2-2 . 10003150 -, f;