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Allan K Clark

Hydrologist, Oklahoma-Texas Water Science Center

Education and Certifications

  • Master of Science, Geology (2002) University of Texas San Antonio

    Bachelor of Science, Geology (1992) University of Texas San Antonio

    Associates Degree, General Studies (1987) Victoria College

Affiliations and Memberships*

  • Professional Geoscientists License (#5877) The State of Texas

Honors and Awards

  • Bernold M. "Bruno" Hanson DEG Excellence of Presentation Award (2008) AAPG Annual convention

    Thirty Years of Service award (2021) USGS

Science and Products

Filter Total Items: 15
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Image: Various Karst Features Along Peace River, Fl

Karst Aquifers

Karst terrain is created from the dissolution of soluble rocks, principally limestone and dolomite. Karst areas are characterized by distinctive landforms (like springs, caves, sinkholes) and a unique hydrogeology that results in aquifers that are highly productive but extremely vulnerable to contamination.
By
Water Resources Mission Area
link

Karst Aquifers

Karst terrain is created from the dissolution of soluble rocks, principally limestone and dolomite. Karst areas are characterized by distinctive landforms (like springs, caves, sinkholes) and a unique hydrogeology that results in aquifers that are highly productive but extremely vulnerable to contamination.
Learn More
link
USGS

Karst Aquifers: Arbuckle-Simpson Aquifer

The Arbuckle-Simpson aquifer, which underlies more than 500 square miles in south central Oklahoma, is the principal water source for approximately 39,000 people in several cities in the region. The U.S. Environmental Protection Agency has designated the aquifer's eastern portion as a Sole Source Aquifer, a mechanism to protect drinking water supplies in areas with limited water supply.
By
Water Resources Mission Area
link

Karst Aquifers: Arbuckle-Simpson Aquifer

The Arbuckle-Simpson aquifer, which underlies more than 500 square miles in south central Oklahoma, is the principal water source for approximately 39,000 people in several cities in the region. The U.S. Environmental Protection Agency has designated the aquifer's eastern portion as a Sole Source Aquifer, a mechanism to protect drinking water supplies in areas with limited water supply.
Learn More
link
USGS

Karst Aquifers: Basin and Range and Bear River Range Carbonate Aquifers

In the Basin and Range, bedrock is present in the uplifted blocks of the mountain ranges and beneath fill in the valleys. While some of this bedrock is relatively impermeable, fracturing may enable groundwater to circulate through the rock, enlarging and increasing the size and number of pathways for water movement. This can ultimately produce a permeable water-yielding unit.
By
Water Resources Mission Area
link

Karst Aquifers: Basin and Range and Bear River Range Carbonate Aquifers

In the Basin and Range, bedrock is present in the uplifted blocks of the mountain ranges and beneath fill in the valleys. While some of this bedrock is relatively impermeable, fracturing may enable groundwater to circulate through the rock, enlarging and increasing the size and number of pathways for water movement. This can ultimately produce a permeable water-yielding unit.
Learn More
link
USGS

Karst Aquifers: Colorado Plateau Karst

In northern and central Arizona, the Kaibab Limestone and its equivalents are karstic. North of the Grand Canyon, subterranean openings are primarily widely spaced fissures, while south of the Grand Canyon, fissures are more closely spaced and a few shallow caves are present.
By
Water Resources Mission Area
link

Karst Aquifers: Colorado Plateau Karst

In northern and central Arizona, the Kaibab Limestone and its equivalents are karstic. North of the Grand Canyon, subterranean openings are primarily widely spaced fissures, while south of the Grand Canyon, fissures are more closely spaced and a few shallow caves are present.
Learn More
link
USGS

Karst Aquifers: Edwards Balcones Fault Zone Aquifer

The Edwards aquifer is the most transmissive of all the aquifers in Texas and Oklahoma, with large discharges from springs and from flowing and pumped wells. This aquifer demonstrates karst features such as springs and in-stream sinkholes, as well as endangered species.
By
Water Resources Mission Area
link

Karst Aquifers: Edwards Balcones Fault Zone Aquifer

The Edwards aquifer is the most transmissive of all the aquifers in Texas and Oklahoma, with large discharges from springs and from flowing and pumped wells. This aquifer demonstrates karst features such as springs and in-stream sinkholes, as well as endangered species.
Learn More
link
USGS

Karst Aquifers: Edwards-Trinity Plateau Aquifer

The Edwards-Trinity aquifer, located in the Trans-Pecos and the Edwards Plateau areas, is composed of relatively flat-lying rocks that are generally exposed at the land surface. This aquifer is generally recharged by precipitation; water is mostly unconfined in the shallow parts of the aquifer and is confined in the deeper zones.
By
Water Resources Mission Area
link

Karst Aquifers: Edwards-Trinity Plateau Aquifer

The Edwards-Trinity aquifer, located in the Trans-Pecos and the Edwards Plateau areas, is composed of relatively flat-lying rocks that are generally exposed at the land surface. This aquifer is generally recharged by precipitation; water is mostly unconfined in the shallow parts of the aquifer and is confined in the deeper zones.
Learn More
link
USGS

Karst Aquifers: Upper Floridan and Biscayne Aquifers

Covering approximately 100,000 square miles of the southeastern United States, the Floridan aquifer system (FAS) is one of the most productive aquifers in the world. The FAS is the primary source of drinking water for almost 10 million people, with nearly 50 percent of all water withdrawals being used for industrial purposes and agricultural irrigation.
By
Water Resources Mission Area
link

Karst Aquifers: Upper Floridan and Biscayne Aquifers

Covering approximately 100,000 square miles of the southeastern United States, the Floridan aquifer system (FAS) is one of the most productive aquifers in the world. The FAS is the primary source of drinking water for almost 10 million people, with nearly 50 percent of all water withdrawals being used for industrial purposes and agricultural irrigation.
Learn More
link
USGS

Karst Aquifers: Madison Aquifer

The Madison aquifer underlies eight states in the U.S. and Canada. It is an important water resource in the northern plains states where surface water supplies are limited and population is increasing. Declining water levels are a major issue for many of the communities that rely on this aquifer.
By
Water Resources Mission Area
link

Karst Aquifers: Madison Aquifer

The Madison aquifer underlies eight states in the U.S. and Canada. It is an important water resource in the northern plains states where surface water supplies are limited and population is increasing. Declining water levels are a major issue for many of the communities that rely on this aquifer.
Learn More
link
USGS

Karst Aquifers: Midwest Paleozoic Carbonate Aquifers

The porosity of carbonate and dolomitic units in Midwest Paleozoic rocks has been enhanced by dissolution, and in many areas these rocks have undergone extensive karst development. This aquifer demonstrates karst features such as disappearing streams, springs, and caves.
By
Water Resources Mission Area
link

Karst Aquifers: Midwest Paleozoic Carbonate Aquifers

The porosity of carbonate and dolomitic units in Midwest Paleozoic rocks has been enhanced by dissolution, and in many areas these rocks have undergone extensive karst development. This aquifer demonstrates karst features such as disappearing streams, springs, and caves.
Learn More
link
USGS

Karst Aquifers: New England Karst Aquifers

The New England Karst Aquifers feature crystalline limestones and marbles, narrow fissures, and some small caves.
By
Water Resources Mission Area
link

Karst Aquifers: New England Karst Aquifers

The New England Karst Aquifers feature crystalline limestones and marbles, narrow fissures, and some small caves.
Learn More
link
USGS

Karst Aquifers: Ozark Plateau Karst Aquifers

The Ozark Plateaus aquifer system consists of two aquifers, the Springfield Plateau aquifer and the Ozark aquifer, and an intervening confining unit. The system consists of mostly of carbonate rocks that are Cambrian through Mississippian in age.
By
Water Resources Mission Area
link

Karst Aquifers: Ozark Plateau Karst Aquifers

The Ozark Plateaus aquifer system consists of two aquifers, the Springfield Plateau aquifer and the Ozark aquifer, and an intervening confining unit. The system consists of mostly of carbonate rocks that are Cambrian through Mississippian in age.
Learn More
link
USGS

Karst Aquifers: Roswell Basin Aquifer

The Roswell Artesian Basin consists of an eastward-dipping carbonate aquifer overlain by a leaky evaporitic confining unit, overlain in turn by an unconfined alluvial aquifer. This aquifer provides habitat for several federally listed endangered invertebrate species. Decades of intensive pumping have caused substantial declines in hydraulic head in the aquifer.
By
Water Resources Mission Area
link

Karst Aquifers: Roswell Basin Aquifer

The Roswell Artesian Basin consists of an eastward-dipping carbonate aquifer overlain by a leaky evaporitic confining unit, overlain in turn by an unconfined alluvial aquifer. This aquifer provides habitat for several federally listed endangered invertebrate species. Decades of intensive pumping have caused substantial declines in hydraulic head in the aquifer.
Learn More

Geospatial Dataset for the Geologic Framework and Hydrostratigraphy of the Edwards and Trinity Aquifers Within Parts of Bandera and Kendall Counties, Texas, at 1:24,000

The karstic Edwards and Trinity aquifers are classified as major sources of water in south-central Texas by the Texas Water Development Board, and both are classified as major aquifers by the State of Texas. The purpose of this data release is to present the data that were collected and compiled to describe the geologic framework and hydrostratigraphy within parts of Bandera and Kendall Counties,
By
Oklahoma-Texas Water Science Center

Geospatial Dataset for the Geologic Framework and Hydrostratigraphy of the Edwards and Trinity Aquifers within Northern Medina County, Texas at 1:24,000

This data release supports the U.S. Geological Survey Scientific Investigation Map (SIM) by Clark and others (2020) by documenting the data used to create the geologic maps and describes the geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers for a 442 square-mile area in northern Medina County in south Texas. The karstic Edwards and Trinity aquifers that are the subject o
By
Oklahoma-Texas Water Science Center

Geospatial Dataset of the Geologic Framework and Hydrostratigraphy of the Edwards and Trinity Aquifers within Hays County, Texas at 1:24,000 scale

The Texas Water Development Board classifies the karstic Edwards and Trinity aquifers as major sources of water in south-central Texas. To effectively manage the water resources in the area, detailed maps and descriptions of the geologic framework and hydrostratigraphic units of the aquifers outcropping in Hays County, Tex. are needed. In 2016 and 2018, the U.S. Geological Survey, in cooperation w
By
Oklahoma-Texas Water Science Center

Data Release of the bedrock geology and hydrostratigraphy of the Edwards and Trinity aquifers within the Driftwood and Wimberley 7.5-minute quadrangles, Hays and Comal Counties, Texas

The Edwards and Trinity aquifers are major sources of water in south-central Texas and are both classified as major aquifers by the State of Texas. The population in Hays and Comal Counties is rapidly growing, increasing demands on the area's water resources. To help effectively manage the water resources in the area, refined maps and descriptions of the geologic structures and hydrostratigraphic
By
Geosciences and Environmental Change Science Center

Geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers within parts of Bandera and Kendall Counties, Texas

The karstic Edwards and Trinity aquifers are classified as major sources of water in south-central Texas by the Texas Water Development Board. During 2019–23 the U.S. Geological Survey, in cooperation with the Edwards Aquifer Authority, mapped and described the geology and hydrostratigraphy of the rocks composing the Edwards and Trinity aquifers within parts of Bandera and Kendall Counties from fi
By
Oklahoma-Texas Water Science Center

Geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers within northern Bexar and Comal Counties, Texas

During 2020–22, the U.S. Geological Survey, in cooperation with the Edwards Aquifer Authority, revised a previous publication that described the geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers within northern Bexar and Comal Counties, Texas. This report presents the refined maps and descriptions of geologic framework and hydrostratigraphy of the Edwards and Trinity aqu
By
Oklahoma-Texas Water Science Center

Geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers within northern Medina County, Texas

The karstic Edwards and Trinity aquifers are classified as major sources of water in south-central Texas by the Texas Water Development Board. During 2018–20 the U.S. Geological Survey, in cooperation with the Edwards Aquifer Authority, mapped and described the geologic framework and hydrostratigraphy of the rocks composing the Edwards and Trinity aquifers in northern Medina County from field obse
By
Water Resources Mission Area, Oklahoma-Texas Water Science Center

Geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers within Hays County, Texas

The Edwards and Trinity aquifers are classified as major aquifers by the Texas Water Development Board and are major sources of water in south-central Texas, where Hays County is located. Detailed maps and descriptions of the geologic framework and hydrostratigraphic units (HSUs) of these karstic aquifers in Hays County are needed for water managers to effectively manage groundwater resources in t
By
Water Resources Mission Area, Oklahoma-Texas Water Science Center

Bedrock geology and hydrostratigraphy of the Edwards and Trinity aquifers within the Driftwood and Wimberley 7.5-minute quadrangles, Hays and Comal Counties, Texas

The Edwards and Trinity aquifers are major sources of water in south-central Texas and are both classified as major aquifers by the State of Texas. The population in Hays and Comal Counties is rapidly growing, increasing demands on the area’s water resources. To help effectively manage the water resources in the area, refined maps and descriptions of the geologic structures and hydrostratigraphic
By
Groundwater and Streamflow Information Program, Geosciences and Environmental Change Science Center

Geologic framework, hydrostratigraphy, and ichnology of the Blanco, Payton, and Rough Hollow 7.5-minute quadrangles, Blanco, Comal, Hays, and Kendall Counties, Texas

This report presents the geologic framework, hydro­stratigraphy, and ichnology of the Trinity and Edwards Groups in the Blanco, Payton, and Rough Hollow 7.5-minute quad­rangles in Blanco, Comal, Hays, and Kendall Counties, Texas. Rocks exposed in the study area are of the Lower Cretaceous Trinity Group and lower part of the Fort Terrett Formation of the Lower Cretaceous Edwards Group. The mapped u
By
Groundwater and Streamflow Information Program, Geosciences and Environmental Change Science Center, Oklahoma-Texas Water Science Center

Geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers within northern Bexar and Comal Counties, Texas

During 2014–16, the U.S. Geological Survey, in cooperation with the Edwards Aquifer Authority, documented the geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers within northern Bexar and Comal Counties, Texas. The Edwards and Trinity aquifers are major sources of water for agriculture, industry, and urban and rural communities in south-central Texas. Both the Edwards and
By
Water Resources Mission Area, Geosciences and Environmental Change Science Center, Oklahoma-Texas Water Science Center

Geologic and hydrostratigraphic map of the Anhalt, Fischer, and Spring Branch 7.5-minute quadrangles, Blanco, Comal, and Kendall Counties, Texas

This report describes the geology and hydrostratigraphy of the Edwards and Trinity Groups in the Anhalt, Fischer, and Spring Branch 7.5-minute quadrangles, Blanco, Comal, and Kendall Counties, Texas. The hydrostratigraphy was defined based on variations in the amount and type of porosity of each lithostratigraphic unit, which varies depending on the unit’s original depositional environment, lithol
By
Water Resources Mission Area, Groundwater and Streamflow Information Program, Geosciences and Environmental Change Science Center, Oklahoma-Texas Water Science Center

Geology and hydrostratigraphy of Guadalupe River State Park and Honey Creek State Natural Area, Kendall and Comal Counties, Texas

Hydrogeologic mapping and descriptions of the lithostratigraphy and hydrostratigraphy of Guadalupe River State Park and Honey Creek State Natural Area, Kendall and Comal Counties, Texas, are presented in this first detailed 1:24,000 geologic map, along with proposed names and descriptions of the hydrostratigraphic units in the study area. Variations in the amount and type of porosity of the lithos
By
Water Resources Mission Area, Oklahoma-Texas Water Science Center, Geosciences and Environmental Change Science Center

Geologic map of the Edwards Aquifer recharge zone, south-central Texas

No abstract available.

Geologic framework and hydrogeologic characteristics of the Glen Rose limestone, Camp Stanley Storage Activity, Bexar County, Texas

The Trinity aquifer is a regional water source in the Hill Country of south-central Texas that supplies water for agriculture, commercial, domestic, and stock purposes. Rocks of the Glen Rose Limestone, which compose the upper zone and upper part of the middle zone of the Trinity aquifer, crop out at the Camp Stanley Storage Activity (CSSA), a U.S. Army weapons and munitions supply, maintenance, a
By
Water Resources Mission Area, Oklahoma-Texas Water Science Center
Filter Total Items: 21

Characterizing the subsurface geology in and around the U.S. Army Camp Stanley Storage Activity, south-central Texas

Several U.S. Geological Survey projects, supported by the National Cooperative Geologic Mapping Program, have used multi-disciplinary approaches over a 14-year period to reveal the surface and subsurface geologic frameworks of the Edwards and Trinity aquifers of central Texas and the Arbuckle-Simpson aquifer of south-central Oklahoma. Some of the project achievements include advancements in hydros
Authors
Charles D. Blome, Allan K. Clark
By
Groundwater and Streamflow Information Program, Geosciences and Environmental Change Science Center, Oklahoma-Texas Water Science Center

U.S. Geological Survey Karst Interest Group Proceedings, San Antonio, Texas, May 16–18, 2017

Introduction and AcknowledgmentsKarst aquifer systems are present throughout parts of the United States and some of its territories, and have developed in carbonate rocks (primarily limestone and dolomite) and evaporites (gypsum, anhydrite, and halite) that span an interval of time encompassing more than 550 million years. The depositional environments, diagenetic processes, post-depositional tect
By
Water Resources Mission Area

Three-dimensional model of the hydrostratigraphy and structure of the area in and around the U.S. Army-Camp Stanley Storage Activity Area, northern Bexar County, Texas

A three-dimensional model of the Camp Stanley Storage Activity area defines and illustrates the surface and subsurface hydrostratigraphic architecture of the military base and adjacent areas to the south and west using EarthVision software. The Camp Stanley model contains 11 hydrostratigraphic units in descending order: 1 model layer representing the Edwards aquifer; 1 model layer representing the
Authors
Michael P. Pantea, Charles D. Blome, Allan K. Clark
By
Groundwater and Streamflow Information Program, Geosciences and Environmental Change Science Center

Key subsurface data help to refine Trinity aquifer hydrostratigraphic units, south-central Texas

The geologic framework and hydrologic characteristics of aquifers are important components for studying the nation’s subsurface heterogeneity and predicting its hydraulic budgets. Detailed study of an aquifer’s subsurface hydrostratigraphy is needed to understand both its geologic and hydrologic frameworks. Surface hydrostratigraphic mapping can also help characterize the spatial distribution and
Authors
Charles D. Blome, Allan K. Clark
By
Groundwater and Streamflow Information Program, Geosciences and Environmental Change Science Center

Hydrogeologic aspects of the Knippa Gap area in eastern Uvalde and western Medina counties, Texas

The Edwards aquifer is the primary source of potable water for the San Antonio area in south-central Texas. The Knippa Gap area is a structural low (trough) postulated to channel or restrict flow in the Edwards aquifer in eastern Uvalde and western Medina Counties, Tex. To better understand the function of the Knippa Gap, the U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engin
Authors
Rebecca B. Lambert, Allan K. Clark, Diana E. Pedraza, Robert R. Morris
By
Water Resources Mission Area, Oklahoma-Texas Water Science Center

U.S. Geological Survey Karst Interest Group Proceedings, Carlsbad, New Mexico, April 29-May 2, 2014

Karst aquifer systems are present throughout parts of the United States and some of its territories, and have developed in carbonate rocks (primarily limestone and dolomite) that span an interval of time encompassing more than 550 million years. The depositional environments, diagenetic processes, post-depositional tectonic events, and geochemical weathering processes that form karst aquifers are
Authors
Eve L. Kuniansky, Lawrence E. Spangler
By
Water Resources Mission Area, Utah Water Science Center

Geologic framework, structure, and hydrogeologic characteristics of the Knippa Gap area in eastern Uvalde and western Medina Counties, Texas

The Edwards aquifer is the primary source of potable water for the San Antonio area in south-central Texas. The Knippa Gap was postulated to channel or restrict flow in the Edwards aquifer in eastern Uvalde County, and its existence was based on a series of numerical simulations of groundwater flow in the aquifer. To better understand the function of the area known as the Knippa Gap as it pertains
Authors
Allan K. Clark, Diana E. Pedraza, Robert R. Morris
By
Water Resources Mission Area, Oklahoma-Texas Water Science Center

Development of a geodatabase for springs within and surrounding outcrops of the Trinity aquifer in northern Bexar County, Texas, 2010-11

The Trinity aquifer is an important source of groundwater in central Texas, including Bexar County, where population growth has resulted in an increased demand for water (Ashworth, 1983; Mace and others, 2000). Numerous springs issue from rock outcrops within and surrounding the Trinity aquifer in northern Bexar County (fig. 1). The effects of increased groundwater withdrawals from the Trinity aqu
Authors
Allan K. Clark, Diane E. Pedraza
By
Water Resources Mission Area, Oklahoma-Texas Water Science Center

Geodatabase and characteristics of springs within and surrounding the Trinity aquifer outcrops in northern Bexar County, Texas, 2010--11

The U.S. Geological Survey, in cooperation with the Trinity Glen Rose Groundwater Conservation District, the Edwards Aquifer Authority, and the San Antonio River Authority, developed a geodatabase of springs within and surrounding the Trinity aquifer outcrops in a 331-square-mile study area in northern Bexar County, Texas. The data used to develop the geodatabase were compiled from existing report
Authors
Allan K. Clark, Diana E. Pedraza, Robert R. Morris, Travis J. Garcia
By
Water Resources Mission Area, Oklahoma-Texas Water Science Center

Groundwater levels and water-quality observations pertaining to the Austin Group, Bexar County, Texas, 2009-11

The U.S. Geological Survey, in cooperation with the San Antonio Water System, examined groundwater-level altitudes (groundwater levels) and water-quality data pertaining to the Austin Group in Bexar County, Texas, during 2009–11. Hydrologic data collected included daily mean groundwater levels collected at seven sites in the study area. Water-quality samples were collected at six sites in the stud
Authors
J.R. Banta, Allan K. Clark
By
Water Resources Mission Area, Oklahoma-Texas Water Science Center

Geologic framework and hydrogeologic characteristics in the southern part of the Rancho Diana Natural Area, northern Bexar County, Texas, 2008-10

The area designated by the city of San Antonio as the Rancho Diana Natural Area is in northern Bexar County, near San Antonio, Texas. During 2008-10, the U.S. Geological Survey, in cooperation with the city of San Antonio, documented the geologic framework and mapped the hydrogeologic characteristics for the southern part of the Rancho Diana Natural Area. The geologic framework of the study area a
Authors
Allan K. Clark, Robert R. Morris
By
Water Resources Mission Area, Oklahoma-Texas Water Science Center

An Integrated Hydrogeologic and Geophysical Investigation to Characterize the Hydrostratigraphy of the Edwards Aquifer in an Area of Northeastern Bexar County, Texas

In August 2007, the U.S. Geological Survey, in cooperation with the San Antonio Water System, did a hydrogeologic and geophysical investigation to characterize the hydrostratigraphy (hydrostratigraphic zones) and also the hydrogeologic features (karst features such as sinkholes and caves) of the Edwards aquifer in a 16-square-kilometer area of northeastern Bexar County, Texas, undergoing urban dev
Authors
Sachin D. Shah, Bruce D. Smith, Allan K. Clark, Jason Payne
By
Water Resources Mission Area, Oklahoma-Texas Water Science Center

Science and Products

Filter Total Items: 15
link
Image: Various Karst Features Along Peace River, Fl

Karst Aquifers

Karst terrain is created from the dissolution of soluble rocks, principally limestone and dolomite. Karst areas are characterized by distinctive landforms (like springs, caves, sinkholes) and a unique hydrogeology that results in aquifers that are highly productive but extremely vulnerable to contamination.
By
Water Resources Mission Area
link

Karst Aquifers

Karst terrain is created from the dissolution of soluble rocks, principally limestone and dolomite. Karst areas are characterized by distinctive landforms (like springs, caves, sinkholes) and a unique hydrogeology that results in aquifers that are highly productive but extremely vulnerable to contamination.
Learn More
link
USGS

Karst Aquifers: Arbuckle-Simpson Aquifer

The Arbuckle-Simpson aquifer, which underlies more than 500 square miles in south central Oklahoma, is the principal water source for approximately 39,000 people in several cities in the region. The U.S. Environmental Protection Agency has designated the aquifer's eastern portion as a Sole Source Aquifer, a mechanism to protect drinking water supplies in areas with limited water supply.
By
Water Resources Mission Area
link

Karst Aquifers: Arbuckle-Simpson Aquifer

The Arbuckle-Simpson aquifer, which underlies more than 500 square miles in south central Oklahoma, is the principal water source for approximately 39,000 people in several cities in the region. The U.S. Environmental Protection Agency has designated the aquifer's eastern portion as a Sole Source Aquifer, a mechanism to protect drinking water supplies in areas with limited water supply.
Learn More
link
USGS

Karst Aquifers: Basin and Range and Bear River Range Carbonate Aquifers

In the Basin and Range, bedrock is present in the uplifted blocks of the mountain ranges and beneath fill in the valleys. While some of this bedrock is relatively impermeable, fracturing may enable groundwater to circulate through the rock, enlarging and increasing the size and number of pathways for water movement. This can ultimately produce a permeable water-yielding unit.
By
Water Resources Mission Area
link

Karst Aquifers: Basin and Range and Bear River Range Carbonate Aquifers

In the Basin and Range, bedrock is present in the uplifted blocks of the mountain ranges and beneath fill in the valleys. While some of this bedrock is relatively impermeable, fracturing may enable groundwater to circulate through the rock, enlarging and increasing the size and number of pathways for water movement. This can ultimately produce a permeable water-yielding unit.
Learn More
link
USGS

Karst Aquifers: Colorado Plateau Karst

In northern and central Arizona, the Kaibab Limestone and its equivalents are karstic. North of the Grand Canyon, subterranean openings are primarily widely spaced fissures, while south of the Grand Canyon, fissures are more closely spaced and a few shallow caves are present.
By
Water Resources Mission Area
link

Karst Aquifers: Colorado Plateau Karst

In northern and central Arizona, the Kaibab Limestone and its equivalents are karstic. North of the Grand Canyon, subterranean openings are primarily widely spaced fissures, while south of the Grand Canyon, fissures are more closely spaced and a few shallow caves are present.
Learn More
link
USGS

Karst Aquifers: Edwards Balcones Fault Zone Aquifer

The Edwards aquifer is the most transmissive of all the aquifers in Texas and Oklahoma, with large discharges from springs and from flowing and pumped wells. This aquifer demonstrates karst features such as springs and in-stream sinkholes, as well as endangered species.
By
Water Resources Mission Area
link

Karst Aquifers: Edwards Balcones Fault Zone Aquifer

The Edwards aquifer is the most transmissive of all the aquifers in Texas and Oklahoma, with large discharges from springs and from flowing and pumped wells. This aquifer demonstrates karst features such as springs and in-stream sinkholes, as well as endangered species.
Learn More
link
USGS

Karst Aquifers: Edwards-Trinity Plateau Aquifer

The Edwards-Trinity aquifer, located in the Trans-Pecos and the Edwards Plateau areas, is composed of relatively flat-lying rocks that are generally exposed at the land surface. This aquifer is generally recharged by precipitation; water is mostly unconfined in the shallow parts of the aquifer and is confined in the deeper zones.
By
Water Resources Mission Area
link

Karst Aquifers: Edwards-Trinity Plateau Aquifer

The Edwards-Trinity aquifer, located in the Trans-Pecos and the Edwards Plateau areas, is composed of relatively flat-lying rocks that are generally exposed at the land surface. This aquifer is generally recharged by precipitation; water is mostly unconfined in the shallow parts of the aquifer and is confined in the deeper zones.
Learn More
link
USGS

Karst Aquifers: Upper Floridan and Biscayne Aquifers

Covering approximately 100,000 square miles of the southeastern United States, the Floridan aquifer system (FAS) is one of the most productive aquifers in the world. The FAS is the primary source of drinking water for almost 10 million people, with nearly 50 percent of all water withdrawals being used for industrial purposes and agricultural irrigation.
By
Water Resources Mission Area
link

Karst Aquifers: Upper Floridan and Biscayne Aquifers

Covering approximately 100,000 square miles of the southeastern United States, the Floridan aquifer system (FAS) is one of the most productive aquifers in the world. The FAS is the primary source of drinking water for almost 10 million people, with nearly 50 percent of all water withdrawals being used for industrial purposes and agricultural irrigation.
Learn More
link
USGS

Karst Aquifers: Madison Aquifer

The Madison aquifer underlies eight states in the U.S. and Canada. It is an important water resource in the northern plains states where surface water supplies are limited and population is increasing. Declining water levels are a major issue for many of the communities that rely on this aquifer.
By
Water Resources Mission Area
link

Karst Aquifers: Madison Aquifer

The Madison aquifer underlies eight states in the U.S. and Canada. It is an important water resource in the northern plains states where surface water supplies are limited and population is increasing. Declining water levels are a major issue for many of the communities that rely on this aquifer.
Learn More
link
USGS

Karst Aquifers: Midwest Paleozoic Carbonate Aquifers

The porosity of carbonate and dolomitic units in Midwest Paleozoic rocks has been enhanced by dissolution, and in many areas these rocks have undergone extensive karst development. This aquifer demonstrates karst features such as disappearing streams, springs, and caves.
By
Water Resources Mission Area
link

Karst Aquifers: Midwest Paleozoic Carbonate Aquifers

The porosity of carbonate and dolomitic units in Midwest Paleozoic rocks has been enhanced by dissolution, and in many areas these rocks have undergone extensive karst development. This aquifer demonstrates karst features such as disappearing streams, springs, and caves.
Learn More
link
USGS

Karst Aquifers: New England Karst Aquifers

The New England Karst Aquifers feature crystalline limestones and marbles, narrow fissures, and some small caves.
By
Water Resources Mission Area
link

Karst Aquifers: New England Karst Aquifers

The New England Karst Aquifers feature crystalline limestones and marbles, narrow fissures, and some small caves.
Learn More
link
USGS

Karst Aquifers: Ozark Plateau Karst Aquifers

The Ozark Plateaus aquifer system consists of two aquifers, the Springfield Plateau aquifer and the Ozark aquifer, and an intervening confining unit. The system consists of mostly of carbonate rocks that are Cambrian through Mississippian in age.
By
Water Resources Mission Area
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Karst Aquifers: Ozark Plateau Karst Aquifers

The Ozark Plateaus aquifer system consists of two aquifers, the Springfield Plateau aquifer and the Ozark aquifer, and an intervening confining unit. The system consists of mostly of carbonate rocks that are Cambrian through Mississippian in age.
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USGS

Karst Aquifers: Roswell Basin Aquifer

The Roswell Artesian Basin consists of an eastward-dipping carbonate aquifer overlain by a leaky evaporitic confining unit, overlain in turn by an unconfined alluvial aquifer. This aquifer provides habitat for several federally listed endangered invertebrate species. Decades of intensive pumping have caused substantial declines in hydraulic head in the aquifer.
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Water Resources Mission Area
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Karst Aquifers: Roswell Basin Aquifer

The Roswell Artesian Basin consists of an eastward-dipping carbonate aquifer overlain by a leaky evaporitic confining unit, overlain in turn by an unconfined alluvial aquifer. This aquifer provides habitat for several federally listed endangered invertebrate species. Decades of intensive pumping have caused substantial declines in hydraulic head in the aquifer.
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Geospatial Dataset for the Geologic Framework and Hydrostratigraphy of the Edwards and Trinity Aquifers Within Parts of Bandera and Kendall Counties, Texas, at 1:24,000

The karstic Edwards and Trinity aquifers are classified as major sources of water in south-central Texas by the Texas Water Development Board, and both are classified as major aquifers by the State of Texas. The purpose of this data release is to present the data that were collected and compiled to describe the geologic framework and hydrostratigraphy within parts of Bandera and Kendall Counties,
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Oklahoma-Texas Water Science Center

Geospatial Dataset for the Geologic Framework and Hydrostratigraphy of the Edwards and Trinity Aquifers within Northern Medina County, Texas at 1:24,000

This data release supports the U.S. Geological Survey Scientific Investigation Map (SIM) by Clark and others (2020) by documenting the data used to create the geologic maps and describes the geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers for a 442 square-mile area in northern Medina County in south Texas. The karstic Edwards and Trinity aquifers that are the subject o
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Oklahoma-Texas Water Science Center

Geospatial Dataset of the Geologic Framework and Hydrostratigraphy of the Edwards and Trinity Aquifers within Hays County, Texas at 1:24,000 scale

The Texas Water Development Board classifies the karstic Edwards and Trinity aquifers as major sources of water in south-central Texas. To effectively manage the water resources in the area, detailed maps and descriptions of the geologic framework and hydrostratigraphic units of the aquifers outcropping in Hays County, Tex. are needed. In 2016 and 2018, the U.S. Geological Survey, in cooperation w
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Oklahoma-Texas Water Science Center

Data Release of the bedrock geology and hydrostratigraphy of the Edwards and Trinity aquifers within the Driftwood and Wimberley 7.5-minute quadrangles, Hays and Comal Counties, Texas

The Edwards and Trinity aquifers are major sources of water in south-central Texas and are both classified as major aquifers by the State of Texas. The population in Hays and Comal Counties is rapidly growing, increasing demands on the area's water resources. To help effectively manage the water resources in the area, refined maps and descriptions of the geologic structures and hydrostratigraphic
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Geosciences and Environmental Change Science Center

Geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers within parts of Bandera and Kendall Counties, Texas

The karstic Edwards and Trinity aquifers are classified as major sources of water in south-central Texas by the Texas Water Development Board. During 2019–23 the U.S. Geological Survey, in cooperation with the Edwards Aquifer Authority, mapped and described the geology and hydrostratigraphy of the rocks composing the Edwards and Trinity aquifers within parts of Bandera and Kendall Counties from fi
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Oklahoma-Texas Water Science Center

Geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers within northern Bexar and Comal Counties, Texas

During 2020–22, the U.S. Geological Survey, in cooperation with the Edwards Aquifer Authority, revised a previous publication that described the geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers within northern Bexar and Comal Counties, Texas. This report presents the refined maps and descriptions of geologic framework and hydrostratigraphy of the Edwards and Trinity aqu
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Oklahoma-Texas Water Science Center

Geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers within northern Medina County, Texas

The karstic Edwards and Trinity aquifers are classified as major sources of water in south-central Texas by the Texas Water Development Board. During 2018–20 the U.S. Geological Survey, in cooperation with the Edwards Aquifer Authority, mapped and described the geologic framework and hydrostratigraphy of the rocks composing the Edwards and Trinity aquifers in northern Medina County from field obse
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Water Resources Mission Area, Oklahoma-Texas Water Science Center

Geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers within Hays County, Texas

The Edwards and Trinity aquifers are classified as major aquifers by the Texas Water Development Board and are major sources of water in south-central Texas, where Hays County is located. Detailed maps and descriptions of the geologic framework and hydrostratigraphic units (HSUs) of these karstic aquifers in Hays County are needed for water managers to effectively manage groundwater resources in t
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Water Resources Mission Area, Oklahoma-Texas Water Science Center

Bedrock geology and hydrostratigraphy of the Edwards and Trinity aquifers within the Driftwood and Wimberley 7.5-minute quadrangles, Hays and Comal Counties, Texas

The Edwards and Trinity aquifers are major sources of water in south-central Texas and are both classified as major aquifers by the State of Texas. The population in Hays and Comal Counties is rapidly growing, increasing demands on the area’s water resources. To help effectively manage the water resources in the area, refined maps and descriptions of the geologic structures and hydrostratigraphic
By
Groundwater and Streamflow Information Program, Geosciences and Environmental Change Science Center

Geologic framework, hydrostratigraphy, and ichnology of the Blanco, Payton, and Rough Hollow 7.5-minute quadrangles, Blanco, Comal, Hays, and Kendall Counties, Texas

This report presents the geologic framework, hydro­stratigraphy, and ichnology of the Trinity and Edwards Groups in the Blanco, Payton, and Rough Hollow 7.5-minute quad­rangles in Blanco, Comal, Hays, and Kendall Counties, Texas. Rocks exposed in the study area are of the Lower Cretaceous Trinity Group and lower part of the Fort Terrett Formation of the Lower Cretaceous Edwards Group. The mapped u
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Groundwater and Streamflow Information Program, Geosciences and Environmental Change Science Center, Oklahoma-Texas Water Science Center

Geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers within northern Bexar and Comal Counties, Texas

During 2014–16, the U.S. Geological Survey, in cooperation with the Edwards Aquifer Authority, documented the geologic framework and hydrostratigraphy of the Edwards and Trinity aquifers within northern Bexar and Comal Counties, Texas. The Edwards and Trinity aquifers are major sources of water for agriculture, industry, and urban and rural communities in south-central Texas. Both the Edwards and
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Water Resources Mission Area, Geosciences and Environmental Change Science Center, Oklahoma-Texas Water Science Center

Geologic and hydrostratigraphic map of the Anhalt, Fischer, and Spring Branch 7.5-minute quadrangles, Blanco, Comal, and Kendall Counties, Texas

This report describes the geology and hydrostratigraphy of the Edwards and Trinity Groups in the Anhalt, Fischer, and Spring Branch 7.5-minute quadrangles, Blanco, Comal, and Kendall Counties, Texas. The hydrostratigraphy was defined based on variations in the amount and type of porosity of each lithostratigraphic unit, which varies depending on the unit’s original depositional environment, lithol
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Water Resources Mission Area, Groundwater and Streamflow Information Program, Geosciences and Environmental Change Science Center, Oklahoma-Texas Water Science Center

Geology and hydrostratigraphy of Guadalupe River State Park and Honey Creek State Natural Area, Kendall and Comal Counties, Texas

Hydrogeologic mapping and descriptions of the lithostratigraphy and hydrostratigraphy of Guadalupe River State Park and Honey Creek State Natural Area, Kendall and Comal Counties, Texas, are presented in this first detailed 1:24,000 geologic map, along with proposed names and descriptions of the hydrostratigraphic units in the study area. Variations in the amount and type of porosity of the lithos
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Water Resources Mission Area, Oklahoma-Texas Water Science Center, Geosciences and Environmental Change Science Center

Geologic map of the Edwards Aquifer recharge zone, south-central Texas

No abstract available.

Geologic framework and hydrogeologic characteristics of the Glen Rose limestone, Camp Stanley Storage Activity, Bexar County, Texas

The Trinity aquifer is a regional water source in the Hill Country of south-central Texas that supplies water for agriculture, commercial, domestic, and stock purposes. Rocks of the Glen Rose Limestone, which compose the upper zone and upper part of the middle zone of the Trinity aquifer, crop out at the Camp Stanley Storage Activity (CSSA), a U.S. Army weapons and munitions supply, maintenance, a
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Water Resources Mission Area, Oklahoma-Texas Water Science Center
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Characterizing the subsurface geology in and around the U.S. Army Camp Stanley Storage Activity, south-central Texas

Several U.S. Geological Survey projects, supported by the National Cooperative Geologic Mapping Program, have used multi-disciplinary approaches over a 14-year period to reveal the surface and subsurface geologic frameworks of the Edwards and Trinity aquifers of central Texas and the Arbuckle-Simpson aquifer of south-central Oklahoma. Some of the project achievements include advancements in hydros
Authors
Charles D. Blome, Allan K. Clark
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Groundwater and Streamflow Information Program, Geosciences and Environmental Change Science Center, Oklahoma-Texas Water Science Center

U.S. Geological Survey Karst Interest Group Proceedings, San Antonio, Texas, May 16–18, 2017

Introduction and AcknowledgmentsKarst aquifer systems are present throughout parts of the United States and some of its territories, and have developed in carbonate rocks (primarily limestone and dolomite) and evaporites (gypsum, anhydrite, and halite) that span an interval of time encompassing more than 550 million years. The depositional environments, diagenetic processes, post-depositional tect
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Water Resources Mission Area

Three-dimensional model of the hydrostratigraphy and structure of the area in and around the U.S. Army-Camp Stanley Storage Activity Area, northern Bexar County, Texas

A three-dimensional model of the Camp Stanley Storage Activity area defines and illustrates the surface and subsurface hydrostratigraphic architecture of the military base and adjacent areas to the south and west using EarthVision software. The Camp Stanley model contains 11 hydrostratigraphic units in descending order: 1 model layer representing the Edwards aquifer; 1 model layer representing the
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Michael P. Pantea, Charles D. Blome, Allan K. Clark
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Groundwater and Streamflow Information Program, Geosciences and Environmental Change Science Center

Key subsurface data help to refine Trinity aquifer hydrostratigraphic units, south-central Texas

The geologic framework and hydrologic characteristics of aquifers are important components for studying the nation’s subsurface heterogeneity and predicting its hydraulic budgets. Detailed study of an aquifer’s subsurface hydrostratigraphy is needed to understand both its geologic and hydrologic frameworks. Surface hydrostratigraphic mapping can also help characterize the spatial distribution and
Authors
Charles D. Blome, Allan K. Clark
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Groundwater and Streamflow Information Program, Geosciences and Environmental Change Science Center

Hydrogeologic aspects of the Knippa Gap area in eastern Uvalde and western Medina counties, Texas

The Edwards aquifer is the primary source of potable water for the San Antonio area in south-central Texas. The Knippa Gap area is a structural low (trough) postulated to channel or restrict flow in the Edwards aquifer in eastern Uvalde and western Medina Counties, Tex. To better understand the function of the Knippa Gap, the U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engin
Authors
Rebecca B. Lambert, Allan K. Clark, Diana E. Pedraza, Robert R. Morris
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Water Resources Mission Area, Oklahoma-Texas Water Science Center

U.S. Geological Survey Karst Interest Group Proceedings, Carlsbad, New Mexico, April 29-May 2, 2014

Karst aquifer systems are present throughout parts of the United States and some of its territories, and have developed in carbonate rocks (primarily limestone and dolomite) that span an interval of time encompassing more than 550 million years. The depositional environments, diagenetic processes, post-depositional tectonic events, and geochemical weathering processes that form karst aquifers are
Authors
Eve L. Kuniansky, Lawrence E. Spangler
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Water Resources Mission Area, Utah Water Science Center

Geologic framework, structure, and hydrogeologic characteristics of the Knippa Gap area in eastern Uvalde and western Medina Counties, Texas

The Edwards aquifer is the primary source of potable water for the San Antonio area in south-central Texas. The Knippa Gap was postulated to channel or restrict flow in the Edwards aquifer in eastern Uvalde County, and its existence was based on a series of numerical simulations of groundwater flow in the aquifer. To better understand the function of the area known as the Knippa Gap as it pertains
Authors
Allan K. Clark, Diana E. Pedraza, Robert R. Morris
By
Water Resources Mission Area, Oklahoma-Texas Water Science Center

Development of a geodatabase for springs within and surrounding outcrops of the Trinity aquifer in northern Bexar County, Texas, 2010-11

The Trinity aquifer is an important source of groundwater in central Texas, including Bexar County, where population growth has resulted in an increased demand for water (Ashworth, 1983; Mace and others, 2000). Numerous springs issue from rock outcrops within and surrounding the Trinity aquifer in northern Bexar County (fig. 1). The effects of increased groundwater withdrawals from the Trinity aqu
Authors
Allan K. Clark, Diane E. Pedraza
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Water Resources Mission Area, Oklahoma-Texas Water Science Center

Geodatabase and characteristics of springs within and surrounding the Trinity aquifer outcrops in northern Bexar County, Texas, 2010--11

The U.S. Geological Survey, in cooperation with the Trinity Glen Rose Groundwater Conservation District, the Edwards Aquifer Authority, and the San Antonio River Authority, developed a geodatabase of springs within and surrounding the Trinity aquifer outcrops in a 331-square-mile study area in northern Bexar County, Texas. The data used to develop the geodatabase were compiled from existing report
Authors
Allan K. Clark, Diana E. Pedraza, Robert R. Morris, Travis J. Garcia
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Water Resources Mission Area, Oklahoma-Texas Water Science Center

Groundwater levels and water-quality observations pertaining to the Austin Group, Bexar County, Texas, 2009-11

The U.S. Geological Survey, in cooperation with the San Antonio Water System, examined groundwater-level altitudes (groundwater levels) and water-quality data pertaining to the Austin Group in Bexar County, Texas, during 2009–11. Hydrologic data collected included daily mean groundwater levels collected at seven sites in the study area. Water-quality samples were collected at six sites in the stud
Authors
J.R. Banta, Allan K. Clark
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Water Resources Mission Area, Oklahoma-Texas Water Science Center

Geologic framework and hydrogeologic characteristics in the southern part of the Rancho Diana Natural Area, northern Bexar County, Texas, 2008-10

The area designated by the city of San Antonio as the Rancho Diana Natural Area is in northern Bexar County, near San Antonio, Texas. During 2008-10, the U.S. Geological Survey, in cooperation with the city of San Antonio, documented the geologic framework and mapped the hydrogeologic characteristics for the southern part of the Rancho Diana Natural Area. The geologic framework of the study area a
Authors
Allan K. Clark, Robert R. Morris
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Water Resources Mission Area, Oklahoma-Texas Water Science Center

An Integrated Hydrogeologic and Geophysical Investigation to Characterize the Hydrostratigraphy of the Edwards Aquifer in an Area of Northeastern Bexar County, Texas

In August 2007, the U.S. Geological Survey, in cooperation with the San Antonio Water System, did a hydrogeologic and geophysical investigation to characterize the hydrostratigraphy (hydrostratigraphic zones) and also the hydrogeologic features (karst features such as sinkholes and caves) of the Edwards aquifer in a 16-square-kilometer area of northeastern Bexar County, Texas, undergoing urban dev
Authors
Sachin D. Shah, Bruce D. Smith, Allan K. Clark, Jason Payne
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Water Resources Mission Area, Oklahoma-Texas Water Science Center

*Disclaimer: Listing outside positions with professional scientific organizations on this Staff Profile are for informational purposes only and do not constitute an endorsement of those professional scientific organizations or their activities by the USGS, Department of the Interior, or U.S. Government

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