Regional Assessment of Groundwater Quality in the Basin and Range, Rio Grande, Coastal Basins, and Central Valley Aquifer Systems of the Southwestern United States

Aquifers are an important source of groundwater for many cities and agricultural communities in the arid and semiarid southwestern United States. The quality of this groundwater is of concern because of the general scarcity of renewable water supplies in the region. To address this concern, the National Water-Quality Assessment (NAWQA) Program of the U.S. Geological Survey is conducting a regional analysis of water quality in the principal aquifer systems (U.S. Geological Survey, 2003) in the Southwest: the Basin and Range basin-fill aquifers in Nevada, Utah, and Arizona; the Rio Grande aquifer system in New Mexico and Colorado; and the Coastal Basin aquifers and the Central Valley aquifer system in California. These principal aquifers consist primarily of unconsolidated basin-fill deposits with similar land- and water-use practices, and water-quality issues. Withdrawals from these aquifers accounted for about one-third of groundwater used for irrigation in the United States in 2000 (Maupin and Barber, 2005). More than 36 million people live above these aquifers, and almost one-half of the water used for public supply in the region is groundwater. Information collected by the NAWQA Program on natural contaminants in groundwater, such as dissolved solids (salinity) and arsenic, and contaminants related to human activities, such as nitrate and pesticides, is available for many basins in the Southwest.

Informational handout about the Basin and Range, Rio Grande, Coastal Basins, and Central Valley Aquifer Systems studies (PDF format, 1Mb)

Detailed information on the hydrogeology of the Basin and Range, Rio Grande, Coastal Basins, and Central Valley Aquifer Systems can be accessed through the USGS Ground Water Atlas of the United States

For more information, contact:
Susan Thiros, Hydrologist