This study, the first of its kind in
more than 50 years, found that the amount of brackish groundwater underlying
the country is more than 800 times the amount currently used each year. With
issues like drought, groundwater depletion, dwindling freshwater supplies, and
demand for groundwater expected to continue to rise, understanding brackish
groundwater supplies can help determine whether they can supplement or replace
taxed freshwater sources in water-stressed areas.
“This assessment lays the foundation
for building a deeper understanding of brackish groundwater resources and how
they might be used to better ensure our water security,” said Jennifer Stanton,
a USGS hydrologist and lead author of this assessment.
In general, brackish groundwater is
groundwater that has a dissolved-solids content greater than freshwater but
less than seawater. It is defined for this assessment as having a
dissolved-solids concentration ranging from 1,000 to 10,000 milligrams per
This new assessment was authorized
by the 2009 SECURE Water Act and builds on a 1965 study, which, for more than five decades, has served as the
primary source of information on the national distribution of brackish
groundwater. By incorporating data from more than 380,000 sites, compared to
about 1,000 for the 1965 study, the 2017 assessment provides more comprehensive,
nationwide data on the quantity and quality of brackish groundwater across the
country. This includes information like chemical composition of the water and
well yields, which are necessary for understanding the potential — at the
national and regional scales — for expanding brackish groundwater development and
for informing decision- and policymakers.
All water naturally contains
dissolved solids that, if present in sufficient concentration, can make the
water brackish, or slightly salty. Sources of these dissolved solids can
include ancient seawater, coastal seawater, dissolution of naturally occurring
minerals, leaching from saline soils, road salt, brine from oil and gas wells,
or other human activities.
The assessment provides data for
states and other public agencies interested in using brackish groundwater. It
also supports the efforts of the U.S. Bureau of Reclamation to promote
sustainable water treatment for brackish aquifers. “The use of brackish
groundwater to augment water supply in the West has been analyzed as a
potential adaptation strategy in a number of studies under Reclamation’s Basin Studies
Program,” said Katharine Dahm, an engineer
with the U.S. Bureau of Reclamation.
Advances in desalination technology
and increases in demand for uses that don’t need high-quality water, like
mining, oil and gas development, and thermoelectric power generation, have led
states like Texas and California to turn to brackish groundwater as an
alternative to freshwater. Click here
to read more.
NGWA has an
information brief on brackish groundwater.
This page was last updated on
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National Ground Water Association
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Westerville, OH 43081
(614 898.7791 outside the US)
fax 614 898.7786