Upper Colorado River Basin Megan Virgili Abstract: When the Upper Colorado River basin is examined from a historical perspective, it is apparent that man's use of the river has contributed to the endangerment of certain species of fish. The Colorado River is one of the world's most regulated rivers; however, regulation necessary to ensure a sufficient quantity of water for the users has also exacted a price in the quantity and quality of water available for fish. Such water depletions have reduced natural river flows required by endangered fish. Natural and human factors in the basin have contributed to reduced water quality. The combined effects of irrigation, mining, urbanization, dams, and reservoirs have been to change the state of the river by increasing sediment load, changing the natural flow of the river, and altering the temperature of the water. These changes in the fishes' natural habitat have lead to decreased fish population and possible extinction of certain species. Key References: Van Steeler, M. & Pitlick, J. (1998, February). Geomorphology and Endangered Fish Habitats of the Upper Colorado River. Water Resources Research, 34(2), 287-302. USGS. (1997B). Effects of Water Quality and Habitat on Composition of Fish Communities in the Upper Colorado River Basin (FS-122-97). Denver, CO: Deacon, J. & Mize, S. Pontius, Dale & SWCA, Inc. (1997). Colorado River Basin Study. Tucson: Western Water Policy Review Advisory Commission.   Return to Water Resources Papers page.