In 1996, the Secretary of the Interior signed a formal decision altering the historical flows from Glen Canyon Dam and establishing the Glen Canyon Dam Adaptive Management Program. Also known as “learning by doing,” adaptive management is a way to evaluate and revise management actions as new infor...
Grand Canyon National Park contains more than 4,000 documented prehistoric and historic sites, and about 420 of these sites are located in proximity to the Colorado River. The lower reaches of Glen Canyon contain an additional 55 sites. In addition to archaeological sites, cultural resources along...
The humpback chub (Gila cypha) is a large and unique freshwater fish found only in the Colorado River Basin. Known to be somewhat rare when it was first described in the 1940s, the humpback chub was placed on the first Federal list of endangered species in 1967. Modeling of the adult humpback...
Power production is included under GCMRC Science activities because minimizing impacts to power production is one of the goals of the Glen Canyon Dam Adaptive Management Program, therefore systematic monitoring and focused research is needed to determine how changes in dam operations to meet various...
The creation of Glen Canyon Dam has had a profound influence on Colorado River recreation. The cold, clear water released from the base of the dam has allowed the development of a vibrant, non-native rainbow trout sport fishery along the 15 mile stretch of river immediately downstream of the dam. Mean...
Today, the Colorado River usually runs clear below Glen Canyon Dam because the dam all but eliminates the mainstem supply of sand to Grand Canyon. Dam-induced changes in both sand supply and flow have disrupted the sedimentary processes that create and maintain Grand Canyon sandbars and associated habitat...
The Colorado River below Glen Canyon Dam has been altered by dam-induced modifications to the river’s flow, temperature, and sediment supply. Nonnative species have also changed the natural system. Nonnative fish are thought to prey on and compete with native fish, including the endangered humpback chub...
Despite the protection afforded national park units, a number of plants and animals that were once native to Grand Canyon National Park can no longer be found with the park’s boundaries. Native plants and animals that are no longer present in a place that was once their home are called extirpated species...
The Kanab ambersnail (Oxyloma haydeni ssp. kanabensis) is a small terrestrial snail that was added to the Federal list of endangered species in 1992. Dependent upon wetland vegetation for food and shelter, the Kanab ambersnail is currently found at three locations: Vaseys Paradise and Elves Chasm—springs...
Rainbow trout (Oncorhynchus mykiss) have a long history in the Grand Canyon region, having first been introduced in Colorado River tributaries like Bright Angel Creek by the National Park Service in the 1920s to create sport fishing opportunities. The completion of Glen Canyon Dam in the 1960s created...
Riparian areas are conspicuous belts of dense, green vegetation along streams and rivers. In the West, riparian areas tend to have higher levels of species diversity, richness, and population densities than adjacent vegetation types, making them of high value to managers, scientists, and the public. Rip...
Scientists and resource managers are interested in water temperature, nutrient concentration, and other water-quality characteristics because they influence a range of ecosystem components, from support of aquatic bacteria and invertebrates to the behavior of fish. In particular, declines of Colorado River...
