5.6 GUNNISON RIVER BASIN
The Gunnison River basin of southwestern Colorado encompasses approximately 8,000 square miles, extending from the Continental Divide in the east to Grand Junction in the west where the Gunnison joins the Colorado River. The watershed comprises portions of seven counties: Mesa, Delta, Montrose, Ouray, Hinsdale, Gunnison, and Saguache. Management of the waters in the Gunnison River basin is under the jurisdiction of Colorado Water Division 4, with its divisional office located in Montrose. As of February 2001, there were approximately 1,844 alluvial wells of record in the Gunnison River basin. The occurrence and distribution of alluvium along the Gunnison River are shown in yellow on Figure 5.6-1.
Elevations in the basin are greater than 13,000 feet in the headwater areas along the Continental Divide, and less than 4,600 feet at the confluence of the Gunnison with the Colorado River. Principal tributaries of the Gunnison River include the Uncompahgre, North Fork Gunnison, Lake Fork Gunnison, East, and Taylor Rivers; and Ohio, Tomichi, and Cochetopa Creeks. Surface water is the main water resource in the basin. The historic average annual discharge of the Gunnison River into the Colorado River at Grand Junction is approximately 1.9 million acre-feet. Diversions for irrigation use were also of this magnitude and represented 99 percent of the total surface-water diversions.
Alluvial ground water, although relatively insignificant in terms of total volume withdrawn, is important for irrigation, public and domestic water supply, and livestock uses. The principal agricultural areas in the Gunnison River basin include the Gunnison area, East River valley, North Fork Gunnison River valley, Delta area, Orchard City-Cedaredge area, and the Uncompahgre River valley. The estimated population of the Gunnison River basin, based on the 2000 Census for the five principal counties, is approximately 80,000 persons.