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Colorado River

Published Nov 4, 2010

Aquatic GAP analysis of the entire Colorado River Basin is being performed by linking ongoing GAP projects in the Lower Colorado River Basin (LCRGAP) and the Upper Colorado River Basin (UCRGAP). Linking the methods, data collection, analysis, and products from the LCRGAP to the UCRGAP will create a seamless integration of both the lower and upper basin to provide a uniform GAP analysis for the entire Colorado River watershed.

Lower Colorado River Basin (LCRB)

The Lower Colorado River Basin (LCRB) has one of the most imperiled fish faunas in the nation and information is needed to develop conservation strategies for the aquatic biota in this regions. Native fishes in the Colorado River Basin have been adversely impacted by modifications in fish communities, hydrology, and river morphology. Although researchers have suggested that full recovery of native fish communities in the Lower Colorado River Basin is not feasible due to political, societal, and economic reasons, the development of criteria for conservation will aid in any future considerations to protect aquatic species in the basin.

Importance:

  • Reports of introduced species occurred as early as the 1870’s and the number of introduced species is now over twice that of native species (Young et al. 2001).
  • Of the 31 fish species native to the LCRB, 17 are listed as Threatened or Endangered under the Federal Endangered Species Act.
  • The Lower Colorado River system provides irrigation water for about 4 million acres of agriculture fields and is a water source for 30 million people in the United States and Mexico (Mueller and Marsh 2002).
  • Water diversions remove all water from reaches of the Lower Salt, Gila, and Colorado rivers and most historic wetlands in the Colorado River Delta; whereas other reaches have been inundated by reservoirs (Mueller and Marsh 2002).
  • The morphology of the basin system has been highly altered by the 20 major dams and extensive system of canals and channelization projects (Mueller and Marsh 2002).
  • Over 90 species have been introduced (Rinne and Janisch 1995) through intentional and unintentional introductions. These introductions are considered one of the primary causes for the decline of native fishes in the region.

Upper Colorado River Basin (UCRB)

The Upper Colorado River Basin (UCRB) has one of the most threatened fish faunas in the United States with only 14 native fish species in the UCRB, most of which have declined in their range and abundance in the last 100 years. Native fishes in the Colorado River Basin have been adversely impacted by modifications to natural flow regimes, physical habitat, stream temperatures and other human-induced agents of environmental change, in addition to the negative effects of invasive species.  The development of criteria for conservation will aid future considerations to protect aquatic species in the basin.

Mission:

  • Determine availability of existing published and unpublished data on the fish distributions and related habitat variables for the Upper Colorado River Basin.
  • Document current land use, stewardship layers, geology, and other landscape-level habitat information (in coordination with the NFHI and Michigan St. Univ.) for the Upper Colorado River Basin.
  • Develop a classification hierarchy for aquatic habitats to provide an ecological basis for determining conservation areas
  • Identify landscape-level habitat metrics associated with native and non native fish presence in the Upper Colorado River Basin.
  • Identify areas of high native fish biodiversity and the habitats associated with those areas for conservation efforts.
  • Classify landscape-level threats to aquatic biota in the UCRB.
  • Link fish distribution maps, landcover, stewardship, and other layers deemed useful by the stakeholders for the upper and lower Colorado River basins to create seamless layers for the Colorado River Basin.

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