All water naturally contains dissolved solids that, if present in sufficient concentration, can make a water resource "brackish", or distastefully salty. The amount of fresh or potable groundwater in storage has declined for many areas in the U.S., leading to concerns about the future availability of water. Using brackish groundwater could supplement or, in some places, replace the use of freshwater sources and enhance our Nation's water security.
The amount of fresh or potable groundwater in storage has declined for many areas in the United States and has led to concerns about the future availability of water for drinking-water, agricultural, industrial, and environmental needs. Use of brackish groundwater could supplement or, in some places, replace the use of freshwater sources and enhance our Nation's water security. However, a better understanding of the location and character of brackish groundwater is needed to expand development of the resource and provide a scientific basis for making policy decisions. To address this need, the Department of Interior's WaterSMART initiative, through the USGS Water Availability and Use Science Program, conducted a national assessment of brackish aquifers.
What is "Brackish"?
All water naturally contains dissolved solids that, if present in sufficient concentration, can make a surface-water or groundwater resource "brackish", typically defined as distastefully salty. Although quantitative definitions of this term vary, it is generally understood that brackish groundwater is water that has a greater dissolved-solids content than occurs in freshwater, but not as much as seawater (35,000 milligrams per liter*). It is considered by many investigators to have dissolved-solids concentration between 1,000 and 10,000 milligrams per liter (mg/L). The term "saline" commonly refers to any water having dissolved-solids concentration greater than 1,000 mg/L and includes the brackish concentration range.
*Milligrams per liter (mg/L) is generally equivalent to parts per million (ppm) when dissolved-solids concentrations are less than about 7,000 mg/L. For larger concentrations, a density correction should be used when converting from mg/L to ppm.
Why Study Brackish Groundwater?
There is growing recognition that brackish groundwater is a resource that could be further developed in many parts of the United States.
Alternative Water Sources Are Needed
In many parts of the country, groundwater withdrawals exceed recharge rates and have caused groundwater-level declines, reductions to the volume of groundwater in storage, lower streamflow and lake levels, or land subsidence. It is expected that the demand for groundwater will continue to increase because of population growth, especially in the arid West. Further, surface-water resources are fully appropriated in many parts of the country, creating additional groundwater demand. Development of brackish groundwater as an alternative water source can help address concerns about the future availability of water and contribute to the water security of the Nation.
Potential Untapped Future Water Resource
Brackish groundwater is potentially abundant. Early studies indicated that mineralized groundwater underlies most of the country. Further, advances in desalination technologies are making treatment and use of brackish groundwater for potable water supply more feasible.
Below are other science projects associated with the National Brackish Groundwater Assessment.
About the USGS National Brackish Groundwater Assessment
National Brackish Groundwater Assessment: Sources of Dissolved Solids in Brackish Groundwater
National Brackish Groundwater Assessment: How is Brackish Groundwater Being Used?
National Brackish Groundwater Assessment: Pilot Saline Studies
National Brackish Groundwater Assessment: Previous Work
- Overview
All water naturally contains dissolved solids that, if present in sufficient concentration, can make a water resource "brackish", or distastefully salty. The amount of fresh or potable groundwater in storage has declined for many areas in the U.S., leading to concerns about the future availability of water. Using brackish groundwater could supplement or, in some places, replace the use of freshwater sources and enhance our Nation's water security.
The amount of fresh or potable groundwater in storage has declined for many areas in the United States and has led to concerns about the future availability of water for drinking-water, agricultural, industrial, and environmental needs. Use of brackish groundwater could supplement or, in some places, replace the use of freshwater sources and enhance our Nation's water security. However, a better understanding of the location and character of brackish groundwater is needed to expand development of the resource and provide a scientific basis for making policy decisions. To address this need, the Department of Interior's WaterSMART initiative, through the USGS Water Availability and Use Science Program, conducted a national assessment of brackish aquifers.
Sources/Usage: Public Domain.Groundwater in basin-fill aquifers of the Southwest U.S. often increases in dissolved-solids content as it travels along its flow path as a result of geochemical interactions with the aquifer matrix and through evaporative processes. At the end of its flowpath, groundwater may be brackish or saline and discharges to the surface through springs, such this one in Death Valley shown in the photograph above. (Credit: David Anning, USGS) What is "Brackish"?
All water naturally contains dissolved solids that, if present in sufficient concentration, can make a surface-water or groundwater resource "brackish", typically defined as distastefully salty. Although quantitative definitions of this term vary, it is generally understood that brackish groundwater is water that has a greater dissolved-solids content than occurs in freshwater, but not as much as seawater (35,000 milligrams per liter*). It is considered by many investigators to have dissolved-solids concentration between 1,000 and 10,000 milligrams per liter (mg/L). The term "saline" commonly refers to any water having dissolved-solids concentration greater than 1,000 mg/L and includes the brackish concentration range.
*Milligrams per liter (mg/L) is generally equivalent to parts per million (ppm) when dissolved-solids concentrations are less than about 7,000 mg/L. For larger concentrations, a density correction should be used when converting from mg/L to ppm.
Why Study Brackish Groundwater?
There is growing recognition that brackish groundwater is a resource that could be further developed in many parts of the United States.
Alternative Water Sources Are Needed
In many parts of the country, groundwater withdrawals exceed recharge rates and have caused groundwater-level declines, reductions to the volume of groundwater in storage, lower streamflow and lake levels, or land subsidence. It is expected that the demand for groundwater will continue to increase because of population growth, especially in the arid West. Further, surface-water resources are fully appropriated in many parts of the country, creating additional groundwater demand. Development of brackish groundwater as an alternative water source can help address concerns about the future availability of water and contribute to the water security of the Nation.
Sources/Usage: Public Domain.Percentage change in population by state and decade: 1980-1990, 1990-2000, and 2000-2010. As the population continues to grow in many areas of the U.S., so does the demand for water. (Credit: U.S. Census Bureau. For more information, see Population Distribution and Change 2000-2010.)
Sources/Usage: Public Domain.Available precipitation (difference between precipitation and potential evapotranspiration), an estimate of how much water is available for recharge to the groundwater system or as runoff to streams. Areas with low amounts of average precipitation may not be able to meet the water needs of continued population growth. (Source: USGS Circular 1323) Potential Untapped Future Water Resource
Brackish groundwater is potentially abundant. Early studies indicated that mineralized groundwater underlies most of the country. Further, advances in desalination technologies are making treatment and use of brackish groundwater for potable water supply more feasible.
Sources/Usage: Public Domain.Map of predicted depth to brackish groundwater from Brackish Groundwater In The United States (USGS Professional Paper 1833). - Science
Below are other science projects associated with the National Brackish Groundwater Assessment.
About the USGS National Brackish Groundwater Assessment
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.National Brackish Groundwater Assessment: Sources of Dissolved Solids in Brackish Groundwater
A variety of conditions and mechanisms can cause groundwater to become brackish. An understanding of the sources of dissolved solids that contribute to the formation of brackish groundwater can help determine where brackish aquifers are likely to exist and can provide clues about other characteristics, such as the chemical composition, of brackish aquifers.National Brackish Groundwater Assessment: How is Brackish Groundwater Being Used?
Industry and public drinking-water suppliers are increasingly turning to brackish groundwater to supplement or replace the use of freshwater. Brackish groundwater is either directly used or treated.National Brackish Groundwater Assessment: Pilot Saline Studies
Three pilot studies were conducted (2010-2012) to assess saline groundwater resources at regional scales. The goals of the pilot studies were to determine the availability of data for assessing the distribution and character of saline groundwater and test and develop methodologies for assessing the resource.National Brackish Groundwater Assessment: Previous Work
Interest in the distribution and classification of brackish groundwater for use as a source of water supply has been longstanding. These studies provided valuable background for the National Brackish Groundwater Assessment. - Data
- Publications