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National Water Census

Dept. of Interior WaterSMART activities

Dept. of Interior WaterSMART activities

Colorado River Basin Focus Area Study

Map of Colorado River Basin. - click to enlarge
Map of Colorado River Basin. - click to enlarge
The Colorado River Basin covers about 246,000 square miles, including parts of the seven "basin States" of Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming and also flows into Mexico. The river supplies water to more than 30 million people, irrigates nearly 4 million acres of cropland in the U.S. and Mexico, and supplies hydropower plants that generate more than 10 billion kilowatt-hours annually. Water from the river also provides for recreation and an array of environmental benefits, supporting a wide diversity of fish and wildlife and their habitats, and preserving flow and water-dependent ecological systems. Increasing population, decreasing stream flows, and the uncertain effects of a changing climate call for a better understanding of water-use and water-availability in the Colorado River Basin.

The USGS coordinates the Colorado River Basin Focus Area Study with the Bureau of Reclamation WaterSMART Basin Study Program. The purpose of the Reclamation study is to define the extent of water supply and demand imbalances in the Colorado River Basin through the year 2060. The Reclamation study also will develop and analyze strategies to resolve those imbalances under a range of conditions that could occur during the next 50 years.

The USGS study complements the Reclamation study by focusing on components of the water budget that are less well understood. Through stakeholder consultation, the USGS has identified the following major components of the basin water budget for investigation. Better quantification of these components of the basin water budget will provide water managers with increased knowledge of water sources and water movement and enhance their ability to make informed resource management decisions about human and ecological water needs.

  1. Estimation of current water use and historical trends in water use into the future. The water-use component of the study will expand the collected water-use data to include information from some uses not currently estimated (e.g., self-supplied commercial). Existing water-use data also will be re-aggregated from a county distribution to an 8-digit hydrologic unit code distribution (HUC-8) to facilitate water-management applications. Where possible, the USGS will estimate consumptive uses using remote sensing and mass balance techniques.

  2. Regional and field scale assessments of evapotranspiration and the dynamic variation in snowpack water content. Evapotranspiration and variation of the water content in the mountain snowpack (including volume and timing of snow-water releases) are important components of the water budget in the Colorado River Basin. These budget components are difficult to measure, especially over such a large area. This study will employ several recently developed remote-sensing techniques, coupled with new and existing ground-based measurements, to extrapolate evapotranspiration across the entire Colorado River Basin. Recently developed snow-water models also will be applied and calibrated. These data will aid in identifying water supply and consumptive use in irrigated agricultural areas – one of the largest water-use categories in the Colorado River Basin.

  3. Estimation of groundwater discharge to streams and rivers. Groundwater contributions to streams in the Colorado River Basin is a relatively poorly understood component of the regional water budget. Preliminary studies by the USGS indicate that somewhere between 20 and 60 percent of the surface-water flow in the upper Basin is derived from groundwater discharge. Future development of groundwater in the basin could have significant effects on surface-water flows. Identification of stream reaches that receive large amounts of groundwater discharge will be a major effort in the upper Colorado River Basin during the study. The geologic controls on groundwater flow will be refined and stream reaches likely to be receiving significant groundwater discharge will be identified. Natural and anthropogenic chemical tracers will be measured to confirm this groundwater discharge and estimate the relative contribution. This effort will provide a map indicating where and how much groundwater shows up in the surface-water flow system.

More information on research being conducted as part of the WaterSMART Colorado basin focus area study is available in this USGS factsheet.

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