The Chicot aquifer system underlies an area of approximately 9,500 mi2 in southwestern Louisiana and is located within the Gulf Coastal Plain physiographic province. The region includes all or parts of 15 parishes -- Vernon, Rapides, Evangeline, Allen, Beauregard, Calcasieu, Jefferson Davis, Acadia, St. Landry, Lafayette, St. Martin, Cameron, Iberia, Vermilion, and St. Mary. The Chicot aquifer system is a major source of groundwater for southwestern Louisiana, accounts for approximately 48 percent of all groundwater use in the State, and provides freshwater for public supply, industry, agriculture, and aquaculture (Collier and Sargent, 2018). Withdrawals of groundwater have created water-level gradients favorable for saltwater encroachment, and future water-availability and production in the region could be impacted by poor water quality. This product is part of a larger study of the Chicot aquifer system in southwestern Louisiana that will benefit local, State, other Federal cooperators, and stakeholders. The extent given here represents the geographic extent of the Chicot aquifer system in southwestern Louisiana and was created using elevation information from U.S. Geological Survey digital elevation models, surface geology maps, and previously published extents (Lovelace and others, 2004; Casarez, 2020).

The Chicot aquifer system is a vital water resource for Southwestern Louisiana, providing nearly half of the fresh groundwater the region consumes (Sargent, 2011). The aquifer’s surficial confining unit (scu) consists of a wedge-shaped thickening sequence of south to southeastern dipping, interbedded clays and courser material (primarily sand and gravel). In collaboration with the Louisiana Department of Transportation and Development (LDOTD), Sargent and others (2004) extracted data from driller’s logs, geophysical logs, and well construction information for 2094 wells overlying the Chicot aquifer to enhance the delineation of the thickness and occurrence of the aquifer’s surficial confining unit. These data were applied here to create tabular data and a shapefile of discrete points that contain thickness data of the confining unit and tops and bottoms of sand and clay layers within the confining unit. A better understanding of the thickness and extent of the Chicot aquifer’s surficial confining unit will provide a framework for future aquifer characterization and will enhance the understanding of groundwater accessibility and availability for the southeast region. 1. Sargent, B.P., Frederick, C.P., Roberts, F.C., 2004, Thickness data for the Chicot aquifer system surficial confining unit: Louisiana Department of Transportation and Development Water Resources Basic Records Report no. 22, 91 p. 2. Sargent, B.P., 2011, Water use in Louisiana, 2010: Louisiana Department of Transportation and Development Water Resources Special Report no. 17, 135 p.

The Chicot aquifer system is a vital water resource for Southwestern Louisiana, providing nearly half of the fresh groundwater the region consumes (Sargent, 2011). The aquifer’s surficial confining unit (scu) consists of a wedge-shaped thickening sequence of south to southeastern dipping, interbedded clays and courser material (primarily sand and gravel). In collaboration with the Louisiana Department of Transportation and Development (LDOTD), Sargent and others (2004) extracted data from driller’s logs, geophysical logs, and well construction information for 2094 wells overlying the Chicot aquifer to enhance the delineation of the thickness and occurrence of the aquifer’s surficial confining unit. These data were applied here to create tabular data and a shapefile of discrete points that contain thickness data of the confining unit and tops and bottoms of sand and clay layers within the confining unit. A better understanding of the thickness and extent of the Chicot aquifer’s surficial confining unit will provide a framework for future aquifer characterization and will enhance the understanding of groundwater accessibility and availability for the southeast region. 1. Sargent, B.P., Frederick, C.P., Roberts, F.C., 2004, Thickness data for the Chicot aquifer system surficial confining unit: Louisiana Department of Transportation and Development Water Resources Basic Records Report no. 22, 91 p. 2. Sargent, B.P., 2011, Water use in Louisiana, 2010: Louisiana Department of Transportation and Development Water Resources Special Report no. 17, 135 p.

The U.S. Geological Survey (USGS) undertook a 5-year study beginning in 2016 to assess groundwater availability for the aquifers proximal to the Gulf of Mexico from the Texas-Mexico border to the western part of the panhandle of Florida; these aquifers are collectively referred to as the coastal lowlands aquifer system. This study is one of several regional groundwater availability studies being done as part of the USGS Water Availability and Use Science Program. Groundwater from the coastal lowlands aquifer system is used mainly for public, irrigation, and industrial supply. During the first two years of the study, the team developed an updated conceptual model of the hydrogeologic framework of the coastal lowlands aquifer system, and in support, a defining compilation of hydrogeologic data. By referencing the data in this compilation, extents of the coastal lowland aquifers were able to be updated and digitized. This data release contains the shapefiles representing the surficial extents of the respective aquifers within the coastal lowlands: the Chicot aquifer, Evangeline aquifer, Burkeville Confining Unit, Jasper aquifer, and Catahoula to the top of the Vicksburg-Jackson confining unit.

The U.S. Geological Survey (USGS) undertook a 5-year study beginning in 2016 to assess groundwater availability for the aquifers proximal to the Gulf of Mexico from the Texas-Mexico border to the western part of the panhandle of Florida; these aquifers are collectively referred to as the coastal lowlands aquifer system. This study is one of several regional groundwater availability studies being done as part of the USGS Water Availability and Use Science Program. Groundwater from the coastal lowlands aquifer system is used mainly for public, irrigation, and industrial supply. During the first two years of the study, the team developed an updated conceptual model of the hydrogeologic framework of the coastal lowlands aquifer system, and in support, a defining compilation of hydrogeologic data. By referencing the data in this compilation, extents of the coastal lowland aquifers were able to be updated and digitized. This data release contains the shapefiles representing the surficial extents of the respective aquifers within the coastal lowlands: the Chicot aquifer, Evangeline aquifer, Burkeville Confining Unit, Jasper aquifer, and Catahoula to the top of the Vicksburg-Jackson confining unit.

This dataset contain the final 6,298 water-level records that met all threshold criteria and had absolute residuals (ABS_PSEUDO_LEVRES) not exceeding 20 feet and exceeding the 99th percentile. This final dataset is considered a best representation of the true water levels in the aquifer.

This dataset contain the final 6,298 water-level records that met all threshold criteria and had absolute residuals (ABS_PSEUDO_LEVRES) not exceeding 20 feet and exceeding the 99th percentile. This final dataset is considered a best representation of the true water levels in the aquifer.

A hydrogeologic framework was constructed for the Coastal Lowlands aquifer system in southwestern Louisiana. Data from previous hydrogeologic and geologic studies were synthesized and expanded using 2,242 geophysical logs to map four hydrogeologic units: the Chicot aquifer system, Evangeline aquifer, Jasper aquifer system, and Catahoula aquifer. Raster surfaces were created for the base and thickness of each unit to provide a generalized framework to support regional groundwater studies.A table listing the well information and point data used to generate the raster surfaces is included in this data release.

The U.S. Geological Survey (USGS) undertook a 5-year study beginning in 2016 to assess groundwater availability for the aquifers proximal to the Gulf of Mexico from the Texas-Mexico border to the western part of the panhandle of Florida; these aquifers are collectively referred to as the coastal lowlands aquifer system. This study is one of several regional groundwater availability studies being done as part of the USGS Water Availability and Use Science Program. Groundwater from the coastal lowlands aquifer system is used mainly for public, irrigation, and industrial supply. Land-surface subsidence related to groundwater pumping is an issue of ongoing concern within this study area. During the first two years of the study, the team developed an updated conceptual model of the hydrogeologic framework of the aquifer system, which lead to initial estimates of major water budget components such as recharge, surface-water/groundwater exchange, and coastal discharge. This data release documents the hydrogeologic data that were compiled and used to define the hydrogeologic framework.

The U.S. Geological Survey (USGS) undertook a 5-year study beginning in 2016 to assess groundwater availability for the aquifers proximal to the Gulf of Mexico from the Texas-Mexico border to the western part of the panhandle of Florida; these aquifers are collectively referred to as the coastal lowlands aquifer system. This study is one of several regional groundwater availability studies being done as part of the USGS Water Availability and Use Science Program. Groundwater from the coastal lowlands aquifer system is used mainly for public, irrigation, and industrial supply. Land-surface subsidence related to groundwater pumping is an issue of ongoing concern within this study area. During the first two years of the study, the team developed an updated conceptual model of the hydrogeologic framework of the aquifer system, which lead to initial estimates of major water budget components such as recharge, surface-water/groundwater exchange, and coastal discharge. This data release documents the hydrogeologic data that were compiled and used to define the hydrogeologic framework.