About the USGS National Brackish Groundwater Assessment

Science Center Objects

The objectives of the National Brackish Groundwater Assessment were to identify and characterize aquifers that contain brackish groundwater in the United States. For purposes of this study, brackish groundwater is defined as having dissolved solids at concentrations between 1,000 and 10,000 milligrams per liter.

Brackish Playa Lake in Saline Valley, CA

Brackish Playa Lake in Saline Valley, CA. (Credit: David Anning, USGS)

This study provided information about brackish-groundwater resources at national and regional scales and was not for defining site-specific or localized conditions. Study results can be used to identify areas where further evaluation of aquifers containing brackish groundwater will be most productive for potential users of the resource.

Major components of the study included:

  • Compiling existing information to assess brackish aquifers
  • Describing, to the extent that available data permit, dissolved-solids concentrations, other chemical characteristics, horizontal and vertical extents of aquifers containing brackish groundwater, ability of the aquifers to yield water, and current brackish groundwater use
  • Generating national maps of dissolved-solids concentrations
  • Identifying data gaps that limit full characterization of brackish aquifers

The study provided the following improvements upon previous work:

  • An updated national inventory of brackish groundwater: Previous national assessments of the distribution of brackish groundwater used only a limited amount of the dissolved-solids data that currently are available. A more complete set of information was assembled from a wide variety of sources and included more recently collected data.
  • Publication of digital dataset: The national geochemical database from the assessment was released as a digital dataset so that other scientists can conduct assessments tailored to their specific needs. Published digital data relating to brackish groundwater previously were limited to a small number of State and regional studies.
  • Enhanced characterization: The updated dissolved-solids inventory was used to characterize brackish aquifers at a higher spatial resolution than previous national work. In addition to dissolved-solids distribution, other chemical characteristics (such as major-ion concentrations) and hydrogeologic characteristics (such as aquifer material, depth, and hydraulic properties) were assessed to determine brackish groundwater availability. Improved characterization is important for understanding and predicting occurrences in areas with few data, and also for assessing limitations imposed by different uses and (or) treatment options.
  • Consistent approach: Although several detailed assessments of brackish aquifers had been conducted at State and regional scales prior to this assessment, the methods differed among the studies. This work described brackish aquifers using consistent data analysis and assessment methods across the country.