5.3 COLORADO RIVER BASIN
The Colorado River basin watershed encompasses an area of approximately 9,830 square miles. The basin defines Water Division 5 with the divisional office in Glenwood Springs. As of early 2001, there were approximately 1,370 alluvial wells of record in the Colorado River basin. The occurrence and distribution of Colorado River alluvium are shown in yellow on Figure 5.3-1.
The headwaters of the main stem are within Rocky Mountain National Park in eastern Grand County. The Colorado River flows southwest some 230 miles through Grand, Eagle, Garfield, and Mesa counties and exits the state at the Utah border. Principal tributaries are the Fraser, Blue, Eagle, and Roaring Fork Rivers. Surface water is the principal water resource in the basin. The Colorado River represents the largest surface-water outflow in the state with over 4.6 million acre-feet of water leaving annually. Agriculture dominates the use of the basin’s water resources, with diversions of approximately 2.2 million acre-feet for the irrigation of 300,000 acres. Between 450,000 and 600,000 acre-feet of water are also diverted annually from the basin to eastern Colorado.
Alluvial ground-water resources are used for public water supply and agricultural irrigation, and represent an important resource in rural areas for domestic supplies. The principal agricultural area is the Grand Valley from Palisade to Fruita; other agricultural areas include Plateau Creek (Collbran area), Colorado River Valley from New Castle to Parachute, and the Roaring Fork Valley. The estimated population of the Colorado River basin, based on the 2000 census of the six major counties within the basin, is slightly over 253,000 people.