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.
Southern Midcontinent Pilot Study
Principal Investigator: Noel Osborn
The hydrogeology, distribution, and volume of saline water in 22 aquifers in the southern midcontinent of the United States were evaluated to provide information about saline groundwater resources that may be used to reduce dependency on freshwater resources. Those aquifers underlie six States in the southern midcontinent-Arkansas, Kansas, Louisiana, Missouri, Oklahoma, and Texas-and adjacent areas including all or parts of Alabama, Colorado, Florida, Illinois, Kentucky, Mississippi, Nebraska, New Mexico, South Dakota, Tennessee, and Wyoming and some offshore areas of the Gulf of Mexico. Saline waters of the aquifers were evaluated by defining salinity zones; digitizing data, primarily from the Regional Aquifer-System Analysis Program of the U.S. Geological Survey; and computing the volume of saline water in storage.
The distribution of saline groundwater in the southern midcontinent is substantially affected by the hydrogeology and groundwater-flow systems of the aquifers. Many of the aquifers in the southern midcontinent are underlain by one or more aquifers, resulting in vertically stacked aquifers containing groundwaters of varying salinity. Saline groundwater is affected by past and present hydrogeologic conditions. Spatial variation of groundwater salinity in the southern midcontinent is controlled primarily by locations of recharge and discharge areas, groundwater-flow paths and residence time, mixing of freshwater and saline water, and interactions with aquifer rocks and sediments.
- Osborn, N.I., Smith, S.J., and Seger, C.H., 2013, Hydrogeology, distribution, and volume of saline groundwater in the southern midcontinent and adjacent areas of the United States: U.S. Geological Survey Scientific Investigations Report 2013-5017, 58 p.
Southeastern United States Pilot Study
Principal Investigator: Lester Williams
Brackish and saline groundwater resources were assessed in two regional aquifer systems in the southeastern United States to determine their potential for supplementing existing freshwater supplies in the area. These resources were mapped in terms of their dissolved-solids concentrations, estimated mostly from borehole geophysical logs, and supplemented with water-quality data collected from wells with known open intervals. Maps and cross sections were constructed for each of the major hydrogeologic units that depict salinity variations in four zones:
- the freshwater zone, containing dissolved-solids of less than 1,000 milligrams per liter (mg/L);
- the brackish-water zone, containing between 1,000 and 10,000 mg/L of dissolved solids;
- the salinity transition zone, containing between 10,000 and 35,000 mg/L of dissolved solids; and
- the saline-water zone, containing between 35,000 and 100,000 mg/L of dissolved solids.
The brine zone, containing greater than 100,000 mg/L of dissolved solids, was not differentiated from the saline-water zone.
The results of the study indicate brackish groundwater resources are present in a variety of clastic and carbonate rock aquifers ranging in depth from a few hundred feet to several thousand feet or more. Brackish zones were mapped in two aquifers of the Southeastern Coastal Plain aquifer system (the Chattahoochee River aquifer and Black Warrior River aquifer) and two aquifers of the Floridan aquifer system (the Upper and Lower Floridan aquifers). Because of differences in permeability, proximity to recharge areas, and the local presence of relict seawater or brine that has not been fully flushed out of the freshwater flow system, vertical and lateral salinity variations in successively deeper aquifers can be complex. A cross section through southeastern Georgia demonstrates the varying extents of brackish water zones in the Southeastern Coastal Plain and Floridan aquifer systems. Regionally, the shallowest and most accessible brackish groundwater resources are present in the Upper Floridan aquifer, mostly in coastal areas of Georgia, Alabama, South Carolina, and throughout most of the coastal areas in Florida. Deeper, less accessible aquifers containing brackish groundwater resources are present throughout much of the Southeastern Coastal Plain aquifer system in Georgia, Alabama, and South Carolina.
Additional study will be needed to assess the extent, water quality, and potential of using brackish- and saline-water resources to supplement existing freshwater supplies. Major considerations for development include the depth and cost of drilling into these deeper zones, alternatives for brine disposal that may be associated with treatment of brackish water, and the potential yield of these aquifers.
- Miller, J.A., 1986, Hydrogeologic framework of the Floridan aquifer system in Florida and in parts of Georgia, South Carolina, and Alabama: U.S. Geological Survey Professional Paper 1403-B, 91 p. and 33 pl.
- Renken, R.A., 1996, Hydrogeology of the Southeastern Coastal Plain aquifer system in Mississippi, Alabama, Georgia, and South Carolina: U.S. Geological Survey Professional Paper 1410-B, 101 p., 42 pl.
- Williams, L.J., Raines, J.E., and Lanning, A.E., 2013, Geophysical log database for the Floridan aquifer system and southeastern Coastal Plain aquifer system in Florida and parts of Georgia, Alabama, and South Carolina: U.S. Geological Survey Data Series 760
Cretaceous Aquifer System of the Mississippi Embayment Pilot Study
Principal Investigator: Jonathan Gillip
The Mississippi Embayment and underlying Cretaceous groundwater systems are rich in water resources. However, large areas of aquifers have elevated total dissolved-solids concentrations. The Nacatoch Sand and the Tokio Formation of the Cretaceous aquifer system were chosen for investigation since the aquifers are known to have increased salinity as the distance from the outcrop increases. Limited water-quality data are available for deeper aquifers, as other shallower aquifers are used for water supply. Historical geophysical logs were used to determine the properties of the deeper aquifers and the quality of the water contained within. Based on the results of this study, in Arkansas, the Nacatoch Sand contains over 80 million acre feet of water with a TDS (total dissolved solids) concentration between 1,000 and 10,000 mg/L, over 60 million acre feet of water with a TDS concentration between 10,000 and 35,000 mg/L, and nearly 180 million acre feet of water with a TDS concentration over 35,000 mg/L. The Tokio formation, in Arkansas contains over 18 million acre feet of water with a TDS concentration between 1,000 and 10,000 mg/L, over 40 million acre feet of water with a TDS concentration between 10,000 and 35,000 mg/L, and nearly 145 million acre feet of water with a TDS concentration over 35,000 mg/L.
- Gillip, J.A., 2014, Characterization of the structure, clean-sand percentage, dissolved-solids concentrations, and estimated quantity of groundwater in the Upper Cretaceous Nacatoch Sand and Tokio Formation, Arkansas: U.S. Geological Survey Scientific Investigations Report 2014-5068, 23 p.
Below are other science projects associated with the National Brackish Groundwater Assessment.
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: Previous Work
Below are publications associated with the National Brackish Groundwater Assessment.
Characterization of the structure, clean-sand percentage, dissolved-solids concentrations, and estimated quantity of groundwater in the Upper Cretaceous Nacatoch Sand and Tokio Formation, Arkansas
Hydrogeology, distribution, and volume of saline groundwater in the southern midcontinent and adjacent areas of the United States
Geophysical log database for the Floridan aquifer system and southeastern Coastal Plain aquifer system in Florida and parts of Georgia, Alabama, and South Carolina
Hydrogeology of the Southeastern Coastal Plain aquifer system in Mississippi, Alabama, Georgia, and South Carolina
Hydrogeologic framework of the Floridan aquifer system in Florida and in parts of Georgia, South Carolina, and Alabama
- Overview
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.
Southern Midcontinent Pilot Study
Regional aquifer systems in the southern midcontinental U.S. Principal Investigator: Noel Osborn
The hydrogeology, distribution, and volume of saline water in 22 aquifers in the southern midcontinent of the United States were evaluated to provide information about saline groundwater resources that may be used to reduce dependency on freshwater resources. Those aquifers underlie six States in the southern midcontinent-Arkansas, Kansas, Louisiana, Missouri, Oklahoma, and Texas-and adjacent areas including all or parts of Alabama, Colorado, Florida, Illinois, Kentucky, Mississippi, Nebraska, New Mexico, South Dakota, Tennessee, and Wyoming and some offshore areas of the Gulf of Mexico. Saline waters of the aquifers were evaluated by defining salinity zones; digitizing data, primarily from the Regional Aquifer-System Analysis Program of the U.S. Geological Survey; and computing the volume of saline water in storage.
The distribution of saline groundwater in the southern midcontinent is substantially affected by the hydrogeology and groundwater-flow systems of the aquifers. Many of the aquifers in the southern midcontinent are underlain by one or more aquifers, resulting in vertically stacked aquifers containing groundwaters of varying salinity. Saline groundwater is affected by past and present hydrogeologic conditions. Spatial variation of groundwater salinity in the southern midcontinent is controlled primarily by locations of recharge and discharge areas, groundwater-flow paths and residence time, mixing of freshwater and saline water, and interactions with aquifer rocks and sediments.
- Osborn, N.I., Smith, S.J., and Seger, C.H., 2013, Hydrogeology, distribution, and volume of saline groundwater in the southern midcontinent and adjacent areas of the United States: U.S. Geological Survey Scientific Investigations Report 2013-5017, 58 p.
Southeastern United States Pilot Study
Principal Investigator: Lester Williams
Location of study area showing the extent of the Southeastern Coastal Plain and Floridan aquifer systems in the southeastern United States. Brackish and saline groundwater resources were assessed in two regional aquifer systems in the southeastern United States to determine their potential for supplementing existing freshwater supplies in the area. These resources were mapped in terms of their dissolved-solids concentrations, estimated mostly from borehole geophysical logs, and supplemented with water-quality data collected from wells with known open intervals. Maps and cross sections were constructed for each of the major hydrogeologic units that depict salinity variations in four zones:
- the freshwater zone, containing dissolved-solids of less than 1,000 milligrams per liter (mg/L);
- the brackish-water zone, containing between 1,000 and 10,000 mg/L of dissolved solids;
- the salinity transition zone, containing between 10,000 and 35,000 mg/L of dissolved solids; and
- the saline-water zone, containing between 35,000 and 100,000 mg/L of dissolved solids.
The brine zone, containing greater than 100,000 mg/L of dissolved solids, was not differentiated from the saline-water zone.
The results of the study indicate brackish groundwater resources are present in a variety of clastic and carbonate rock aquifers ranging in depth from a few hundred feet to several thousand feet or more. Brackish zones were mapped in two aquifers of the Southeastern Coastal Plain aquifer system (the Chattahoochee River aquifer and Black Warrior River aquifer) and two aquifers of the Floridan aquifer system (the Upper and Lower Floridan aquifers). Because of differences in permeability, proximity to recharge areas, and the local presence of relict seawater or brine that has not been fully flushed out of the freshwater flow system, vertical and lateral salinity variations in successively deeper aquifers can be complex. A cross section through southeastern Georgia demonstrates the varying extents of brackish water zones in the Southeastern Coastal Plain and Floridan aquifer systems. Regionally, the shallowest and most accessible brackish groundwater resources are present in the Upper Floridan aquifer, mostly in coastal areas of Georgia, Alabama, South Carolina, and throughout most of the coastal areas in Florida. Deeper, less accessible aquifers containing brackish groundwater resources are present throughout much of the Southeastern Coastal Plain aquifer system in Georgia, Alabama, and South Carolina.
Additional study will be needed to assess the extent, water quality, and potential of using brackish- and saline-water resources to supplement existing freshwater supplies. Major considerations for development include the depth and cost of drilling into these deeper zones, alternatives for brine disposal that may be associated with treatment of brackish water, and the potential yield of these aquifers.
- Miller, J.A., 1986, Hydrogeologic framework of the Floridan aquifer system in Florida and in parts of Georgia, South Carolina, and Alabama: U.S. Geological Survey Professional Paper 1403-B, 91 p. and 33 pl.
- Renken, R.A., 1996, Hydrogeology of the Southeastern Coastal Plain aquifer system in Mississippi, Alabama, Georgia, and South Carolina: U.S. Geological Survey Professional Paper 1410-B, 101 p., 42 pl.
- Williams, L.J., Raines, J.E., and Lanning, A.E., 2013, Geophysical log database for the Floridan aquifer system and southeastern Coastal Plain aquifer system in Florida and parts of Georgia, Alabama, and South Carolina: U.S. Geological Survey Data Series 760
Cretaceous Aquifer System of the Mississippi Embayment Pilot Study
Map of the West Gulf Coastal Plain, Mississippi embayment, and underlying Cretaceous aquifer study area, including the Nacatoch Sand and Tokio Formation, Arkansas. Principal Investigator: Jonathan Gillip
The Mississippi Embayment and underlying Cretaceous groundwater systems are rich in water resources. However, large areas of aquifers have elevated total dissolved-solids concentrations. The Nacatoch Sand and the Tokio Formation of the Cretaceous aquifer system were chosen for investigation since the aquifers are known to have increased salinity as the distance from the outcrop increases. Limited water-quality data are available for deeper aquifers, as other shallower aquifers are used for water supply. Historical geophysical logs were used to determine the properties of the deeper aquifers and the quality of the water contained within. Based on the results of this study, in Arkansas, the Nacatoch Sand contains over 80 million acre feet of water with a TDS (total dissolved solids) concentration between 1,000 and 10,000 mg/L, over 60 million acre feet of water with a TDS concentration between 10,000 and 35,000 mg/L, and nearly 180 million acre feet of water with a TDS concentration over 35,000 mg/L. The Tokio formation, in Arkansas contains over 18 million acre feet of water with a TDS concentration between 1,000 and 10,000 mg/L, over 40 million acre feet of water with a TDS concentration between 10,000 and 35,000 mg/L, and nearly 145 million acre feet of water with a TDS concentration over 35,000 mg/L.
- Gillip, J.A., 2014, Characterization of the structure, clean-sand percentage, dissolved-solids concentrations, and estimated quantity of groundwater in the Upper Cretaceous Nacatoch Sand and Tokio Formation, Arkansas: U.S. Geological Survey Scientific Investigations Report 2014-5068, 23 p.
- Science
Below are other science projects associated with the National Brackish Groundwater Assessment.
Brackish Groundwater Assessment
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...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: 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. - Publications
Below are publications associated with the National Brackish Groundwater Assessment.
Characterization of the structure, clean-sand percentage, dissolved-solids concentrations, and estimated quantity of groundwater in the Upper Cretaceous Nacatoch Sand and Tokio Formation, Arkansas
The West Gulf Coastal Plain, Mississippi embayment, and underlying Cretaceous aquifers are rich in water resources; however, large parts of the aquifers are largely unusable because of large concentrations of dissolved solids. Cretaceous aquifers are known to have large concentrations of salinity in some parts of Arkansas. The Nacatoch Sand and the Tokio Formation of Upper Cretaceous age were chosAuthorsJonathan A. GillipHydrogeology, distribution, and volume of saline groundwater in the southern midcontinent and adjacent areas of the United States
The hydrogeology, distribution, and volume of saline water in 22 aquifers in the southern midcontinent of the United States were evaluated to provide information about saline groundwater resources that may be used to reduce dependency on freshwater resources. Those aquifers underlie six States in the southern midcontinent—Arkansas, Kansas, Louisiana, Missouri, Oklahoma, and Texas—and adjacent areaAuthorsNoël I. Osborn, S. Jerrod Smith, Christian H. SegerGeophysical log database for the Floridan aquifer system and southeastern Coastal Plain aquifer system in Florida and parts of Georgia, Alabama, and South Carolina
A database of borehole geophysical logs and other types of data files were compiled as part of ongoing studies of water availability and assessment of brackish- and saline-water resources. The database contains 4,883 logs from 1,248 wells in Florida, Georgia, Alabama, South Carolina, and from a limited number of offshore wells of the eastern Gulf of Mexico and the Atlantic Ocean. The logs can be aAuthorsLester J. Williams, Jessica E. Raines, Amanda E. LanningHydrogeology of the Southeastern Coastal Plain aquifer system in Mississippi, Alabama, Georgia, and South Carolina
The Southeastern Coastal Plain aquifer system consists of a thick sequence of unconsolidated to poorly consolidated Cretaceous and Tertiary rocks that extend from Mississippi to South Carolina. Four regional sand and gravel aquifers are separated by three regional confining units of clay, shale, and chalk that do not conform everywhere to stratigraphic boundaries. The change in geologic facies isAuthorsRobert A. RenkenHydrogeologic framework of the Floridan aquifer system in Florida and in parts of Georgia, South Carolina, and Alabama
The Floridan aquifer system of the Southeastern United States is comprised of a thick sequence of carbonate rocks that are mostly of Paleocene to early Miocene age and that are hydraulically connected in varying degrees. The aquifer system consists of a single vertically continuous permeable unit updip and of two major permeable zones (the Upper and Lower Floridan aquifers) separated by one of sevAuthorsJames A. Miller