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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.
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.
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.
Below are data associated with this project.
Below are publications associated with the National Brackish Groundwater Assessment.