Why Study Brackish Groundwater?
Sources of Dissolved Solids in Brackish Groundwater
How is Brackish Groundwater Being Used?
About the Study
Groundwater discharge and rainfall-runoff collect and evaporate from this brackish playa lake in Saline Valley, CA. Photo by USGS hydrologist David Anning.
The objectives of the study are to identify and characterize significant brackish aquifers in the United States. Brackish aquifers are defined for purposes of this study as aquifers that have groundwater within 3,000 ft of land surface, contain dissolved solids at concentrations between 1,000 and 10,000 milligrams per liter, and can yield usable quantities of water.
The study is intended to provide information about brackish aquifers at national and regional scales and is not for defining site-specific or localized conditions. Study results can be used to identify areas where further evaluation of the brackish aquifers will be most productive for potential users of the resource.
Major components of the study include:
- Compiling existing information that can be used 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 will provide 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 will be assembled from a wide variety of sources and will include more recently collected data.
- Publication of digital datasets: The national inventory and selected results will be published as digital datasets so that other scientists can conduct assessments tailored to their specific needs. Published digital data relating to brackish groundwater currently are limited to a small number of state and regional studies.
- Enhanced characterization: The updated dissolved-solids inventory will be 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, residence time, thickness, flow patterns, recharge rates, and hydraulic properties) will be 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 have been conducted at state and regional scales, the methods differed among the studies. This work will describe brackish aquifers using consistent data analysis and assessment methods across the country.
Completion Date: September 2016.
