Trinity Aquiferinteractive map | cross-section
Aquifer Facts
- Aquifer type: confined and unconfined
- Area of outcrop: 10,692 square miles
- Area of subsurface: 21,308 square miles
- Proportion of aquifer with groundwater conservation districts: 88 percent
- Number of counties containing the aquifer: 61
Summary
The Trinity Aquifer is a major aquifer that extends across much of the central and northeastern part of the state. It is composed of several smaller aquifers contained within the Trinity Group. Although referred to differently in different parts of the state, they include the Antlers, Glen Rose, Paluxy, Twin Mountains, Travis Peak, Hensell, and Hosston aquifers. These aquifers consist of limestones, sands, clays, gravels, and conglomerates. Their combined freshwater saturated thickness averages about 600 feet in North Texas and about 1,900 feet in Central Texas.
In general, groundwater is fresh but very hard in the outcrop of the aquifer. Total dissolved solids increase from less than 1,000 milligrams per liter in the east and southeast to between 1,000 and 5,000 milligrams per liter, or slightly to moderately saline, as the depth to the aquifer increases. Sulfate and chloride concentrations also tend to increase with depth.
The aquifer is one of the most extensive and highly used groundwater resources in Texas. Although its primary use is for municipalities, it is also used for irrigation, livestock, and other domestic purposes. Some of the state's largest water level declines, ranging from 350 to more than 1,000 feet, have occurred in counties along the IH-35 corridor from McLennan County to Grayson County. These declines are primarily attributed to municipal pumping, but they have slowed over the past decade as a result of increasing reliance on surface water.
Reports
| ID | Date | Type | Description |
|---|---|---|---|
| Texas Aquifers Study | 12/31/2016 | Legislative Report | Texas Aquifers Study: Groundwater Quantity, Quality, Flow, and Contributions to Surface Water |
| AA09-07 | 11/22/2010 | Aquifer assessment | Reevaluation of desired future conditions for the Trinity Aquifer in Comanche and Erath counties |
| B-6310 | 12/1/1973 | Groundwater bulletin | Reconnaissance Investigation of the Ground-Water Resources of the Brazos River Basin, Texas |
| B-6212 | 7/1/1962 | Groundwater bulletin | Geology and Ground-Water Resources of Uvalde County, Texas |
| B-5911 | 10/1/1959 | Groundwater bulletin | Ground-Water Geology of Bexar County, Texas |
| R-019 | 3/1/1966 | TWDB numbered report | Ground-Water Resources of Guadalupe County, Texas |
| R-350 | 11/1/1999 | TWDB numbered report | Changes in Groundwater Conditions in the Edwards and Trinity Aquifers, 1987-1997, for Portions of Bastrop, Bell, Burnet, Lee, Milam, Travis, and Williamson Counties, Texas |
| R-109 | 3/1/1970 | TWDB numbered report | Ground-Water Resources of Bastrop County, Texas |
| R-160 | 11/1/1972 | TWDB numbered report | Ground-Water Resources of Navarro County, Texas |
| B-5601 | 8/1/1956 | Groundwater bulletin | Geology and Ground-Water Resources of Medina County, Texas |
| B-6004 | 8/1/1960 | Groundwater bulletin | Geology and Ground-Water Resources of Hays County, Texas |
| B-6210 | 5/1/1962 | Groundwater bulletin | Ground-Water Geology of Bandera County, Texas |
| R-046 | 5/1/1967 | TWDB numbered report | Occurrence and Quality of Ground Water in Brown County, Texas |
| R-058 | 8/1/1967 | TWDB numbered report | Occurrence and Quality of Ground Water in Montague County, Texas |
| R-235 | 7/1/1979 | TWDB numbered report | Occurrence, Availability, and Chemical Quality of Ground Water in the Edwards Plateau Region of Texas |
| R-322 | 3/1/1990 | TWDB numbered report | Ground-Water Evaluation in and Adjacent to Dripping Springs, Texas |
| R-276 | 6/1/1983 | TWDB numbered report | Occurrence, Availability, and Quality of Ground Water in Travis County, Texas |
| R-102 | 11/1/1969 | TWDB numbered report | Ground-Water Resources of Kerr County, Texas |
| R-174 | 7/1/1973 | TWDB numbered report | Ground-Water Resources of Blanco County, Texas |
| R-029 | 9/1/1966 | TWDB numbered report | Base-Flow Studies, Upper Guadalupe River Basin, Texas, Quality and Quantity |
| R-273 | 1/1/1983 | TWDB numbered report | Ground-Water Availability of the Lower Cretaceous Formations in the Hill Country of South-Central Texas |
| R-353 | 9/1/2000 | TWDB numbered report | Groundwater Availability of the Trinity Aquifer, Hill Country Area, Texas: Numerical Simulations through 2050 |
| R-224 | 10/1/1978 | TWDB numbered report | Occurrence, Quantity, and Quality of Ground Water in Taylor County, Texas |
| R-331 | 7/1/1991 | TWDB numbered report | Ground-Water Quality Monitoring of the Trinity Aquifer in the Vicinity of Erath County |
| R-269 | 4/1/1982 | TWDB numbered report | Occurrence, Availability and Chemical Quality of Ground Water in the Cretaceous Aquifers of North-Central Texas, Volumes 1 & 2 |
| R-195 | 11/1/1975 | TWDB numbered report | Ground-Water Resources of Part of Central Texas with Emphasis on the Antlers and Travis Peak Formations, Volumes 1 & 2 |
| R-319 | 1/1/1990 | TWDB numbered report | Evaluation of Water Resources in Part of Central Texas |
| R-346 | 3/1/1996 | TWDB numbered report | The Paleozoic and Related Aquifers of Central Texas |
| R-339 | 8/1/1992 | TWDB numbered report | Evaluation of Ground-Water Resources of the Paleozoic and Cretaceous Aquifers in the Hill Country of Central Texas |
| R-349 | 11/1/1999 | TWDB numbered report | Updated Evaluation of Water Resources in Part of North-Central Texas, 1990-1999 |
| R-318 | 1/1/1990 | TWDB numbered report | Evaluation of Water Resources in Part of North-Central Texas |
| R-308 | 8/1/1988 | TWDB numbered report | Occurrence and Quality of Ground Water in Jack County, Texas |
| R-377 | 6/1/2011 | TWDB numbered report | Groundwater Availability Model: Hill Country Portion of the Trinity Aquifer of Texas |
| AA09-02_D | 4/20/2010 | Aquifer assessment | Desired future condition scenarios for the middle and lower Trinity Aquifer in Groundwater Management Area 10 |
| AA10-03_D | 6/10/2010 | Aquifer assessment | Desired future condition scenarios for the Trinity Aquifer in Groundwater Management Area 10 |
| AA10-06 | 7/28/2010 | Aquifer assessment | Desired future condition scenarios for the Trinity Aquifer in Groundwater Management Area 10 |
| GR11-004_MP | 9/26/2011 | GAM run - Management Plan | Management plan information for Prairielands GCD |
| GR10-066_MP | 1/19/2011 | GAM run - Management Plan | Management plan information for Central Texas GCD |
| GR10-034_MP | 10/26/2010 | GAM run - Management Plan | Management plan information for North Texas GCD |
| GR10-032_MP | 9/29/2010 | GAM run - Management Plan | Management plan information for Red River GCD |
| GR10-029_MP | 1/4/2011 | GAM run - Management Plan | Management plan information for Post Oak Savannah GCD |
| GT10-031 | 1/25/2011 | GAM task | Additional results from the analysis completed in GAM Task 10-005 |
| GR10-014_MP | 6/9/2010 | GAM run - Management Plan | Management plan information for Lost Pines GCD |
| GR10-009_MP | 6/9/2010 | GAM run - Management Plan | Management plan information for Clearwater UWCD |
| GR10-004_MP | 4/15/2010 | GAM run - Management Plan | Management plan information for Middle Trinity GCD |
| GR09-033_MP | 7/29/2010 | GAM run - Management Plan | Management plan information for Hays Trinity GCD |
| GR09-031_MP | 7/9/2010 | GAM run - Management Plan | Management plan information for Medina County GCD |
| GR09-030_MP | 10/21/2009 | GAM run - Management Plan | Management plan information for Cow Creek GCD |
| GR09-011 | 9/14/2010 | GAM run | Predictive simulations for the Edwards-Trinity (Plateau) and Trinity aquifers in Groundwater Management Area 9 |
| GR09-012 | 9/14/2010 | GAM run | Predictive simulations for the Edwards-Trinity (Plateau) and Trinity aquifers in Groundwater Management Area 9 |
| GR09-024 | 9/14/2010 | GAM run | Predictive simulations for the Edwards-Trinity (Plateau) and Trinity aquifers in Groundwater Management Area 9 |
| GR09-011_S | 9/13/2010 | GAM run | Predictive simulations for the Edwards-Trinity (Plateau) and Trinity aquifers in Groundwater Management Area 9 |
| GR09-012_S | 9/13/2010 | GAM run | Predictive simulations for the Edwards-Trinity (Plateau) and Trinity aquifers in Groundwater Management Area 9 |
| GR09-024_S | 9/13/2010 | GAM run | Predictive simulations for the Edwards-Trinity (Plateau) and Trinity aquifers in Groundwater Management Area 9 |
| GR09-022_MP | 11/20/2009 | GAM run - Management Plan | Management plan information for Upper Trinity GCD |
| GR09-021_MP | 7/31/2009 | GAM run - Management Plan | Management plan information for Neches & Trinity Valleys GCD |
| GR08-089_MP | 5/20/2009 | GAM run - Management Plan | Management plan information for Lost Pines GCD |
| GR08-083 | 5/17/2010 | GAM run | Additional results from the analysis completed in GAM Run 08-064 |
| GR08-072_MP | 10/3/2008 | GAM run - Management Plan | Management plan information for Middle Trinity GCD |
| GR08-071_MP | 10/3/2008 | GAM run - Management Plan | Management plan information for Neches & Trinity Valleys GCD |
| GR08-070 | 12/2/2008 | GAM run | Predictive and steady-state simulations for the Trinity Aquifer in Groundwater Management Area 9 |
| GR08-069_MP | 9/10/2008 | GAM run - Management Plan | Management plan information for McLennan County GCD |
| GR08-066 | 5/17/2010 | GAM run | Predictive simulation for the Woodbine and Trinity aquifers in Groundwater Management Area 8 |
| GR08-065_MP | 8/22/2008 | GAM run - Management Plan | Management plan information for Northern Trinity GCD |
| GR08-064 | 5/17/2010 | GAM run | Predictive simulation for the Woodbine and Trinity aquifers in Groundwater Management Area 8 |
| GR08-053_MP | 8/1/2008 | GAM run - Management Plan | Management plan information for Fox Crossing Water District |
| GR08-040_MP | 5/30/2008 | GAM run - Management Plan | Management plan information for Saratoga UWCD |
| GR08-030 | 8/19/2008 | GAM run | Predictive simulation for the Trinity Aquifer in Groundwater Management Area 9 |
| GR08-020 | 7/28/2008 | GAM run | Predictive simulation for the Trinity Aquifer in Groundwater Management Area 9 |
| GR08-015 | 7/8/2008 | GAM run | Predictive simulation for the Trinity Aquifer in Groundwater Management Area 9 |
| GR08-005 | 2/11/2008 | GAM run | Predictive simulations for the Trinity Aquifer in Groundwater Management Area 8 |
| GR08-006 | 2/11/2008 | GAM run | Predictive simulations for the Trinity Aquifer in Groundwater Management Area 8 |
| GR07-030 | 10/26/2007 | GAM run | Predictive simulations for the Trinity Aquifer in Groundwater Management Area 8 |
| GR07-024_MP | 9/5/2007 | GAM run - Management Plan | Management plan information for Cow Creek GCD |
| GR07-018 | 7/13/2007 | GAM run | Simulation to document locations and discharges to springs and rivers, and document the water budget in Groundwater Management Area 9 |
| GR07-009 | 6/29/2007 | GAM run | Predictive simulation for the Trinity Aquifer in Groundwater Management Area 8 |
| GR06-012 | 7/31/2006 | GAM run | Predictive simulation for the Trinity Aquifer in Lampasas County (Saratoga UWCD) |
| GR05-039 | 1/3/2006 | GAM run | Predictive simulation for the Trinity Aquifer in Mills County |
| GR05-035 | 9/12/2005 | GAM run | Effects on Guadalupe River flow from various pumping scenarios in the Trinity Aquifer |
| GR05-030 | 7/15/2005 | GAM run | Recharge information for the Carrizo-Wilcox, Edwards-Trinity (Plateau) and Trinity aquifers in Uvalde County |
| GR05-031 | 7/21/2005 | GAM run | Recharge information for the Carrizo-Wilcox and Trinity aquifers in Medina County |
| GR04-018 | 10/7/2004 | GAM run | Recharge rates for the Trinity Aquifer in Hays Trinity GCD |
| GR04-006 | 5/6/2004 | GAM run | Analytical groundwater modeling to estimate water level drawdown in Erath and Comanche counties |
| GR03-034 | 5/14/2004 | GAM run | Analytical groundwater modeling to assess water level drawdown by implementing hypothetical well fields |
| GR03-029 | 10/31/2003 | GAM run | Decadal water level declines for the Upper and Middle Trinity aquifers of the Trinity (Hill Country) GAM |
| GR03-025 | 9/2/2003 | GAM run | Recharge, leakage, and total storage for the Trinity (Hill Country) in Bandera County River Authority and GCD |
| GR03-012 | 7/18/2003 | GAM run | Water budget, storage, and drawdown in 2050 for the Trinity (Hill Country) and Carrizo-Wilcox aquifers in Medina County GCD |
| GR03-011 | 3/21/2003 | GAM run | Water budget by county for the Trinity (Hill Country) Aquifer |
| GR03-005 | 5/20/2003 | GAM run | Estimated water levels at specified locations in the Trinity (Hill Country) GAM |
| GR03-002 | 3/21/2003 | GAM run | Average well yield in Kendall County for the Trinity (Hill Country) Aquifer GAM |
| GR08-084_MAG | 3/5/2009 | GAM run - MAG | Managed available groundwater estimates for the Trinity Aquifer in Groundwater Management Area 8 |
| GR11-008 | 1/27/2012 | GAM run | Trinity Aquifer model runs for Central Texas GCD |
| GR11-005 | 1/26/2012 | GAM run | Trinity Aquifer model runs for Central Texas GCD |
| GR02-001 | 3/21/2003 | GAM run | County water budget for the Trinity (Hill Country) Aquifer GAM |
| GR02-002 | 3/21/2003 | GAM run | County water budget for the Trinity (Hill Country) Aquifer GAM |
| GR11-006 | 2/2/2012 | GAM run | Predictive simulations for the Trinity Aquifer in Clearwater UWCD |
| AA10-29_MAG | 11/29/2011 | Aquifer assessment MAG | Modeled available groundwater for the Trinity Aquifer in Groundwater Management Area 10 |
| CR-1004831116 | 7/11/2012 | Contract report | Aquifer Test and Related Well Information from Public Water Supply Wells in Groundwater Management Area 8 |
| R-380 | 7/1/2011 | TWDB numbered report | Aquifers of Texas |
| GR12-021_MP | 9/4/2012 | GAM run - Management Plan | Management plan data for Headwaters GCD |
| GR12-015_MP | 9/4/2012 | GAM run - Management Plan | Management plan data for Hill Country UWCD |
| CR-1004831114 | 8/9/2012 | Contract report | Ground Water Recharge Model: Calibration and Validation for Remotely-Sensed Dual Coefficient (RDC) GMA8 ET Estimation |
| GR08-011_MP | 4/29/2008 | GAM run - Management Plan | Management plan information for Blanco-Pedernales GCD |
| GR13-001_MP | 1/24/2013 | GAM run - Management Plan | Management plan data for Blanco-Pedernales GCD |
| GR13-013_MP | 7/3/2013 | GAM run - Management Plan | Management plan data for Neches & Trinity Valleys GCD |
| GR13-019_MP | 7/3/2013 | GAM run - Management Plan | Management Plan data for Saratoga UWCD |
| GR13-016_MP | 8/7/2013 | GAM run - Management Plan | Management plan data for Middle Trinity GCD |
| GT13-029_TERS | 9/19/2013 | GAM task - Total Estimated Recoverable Storage | Total Estimated Recoverable Storage for aquifers in Groundwater Management Area 6 |
| GT13-030_TERS | 10/2/2013 | GAM task - Total Estimated Recoverable Storage | Total Estimated Recoverable Storage for aquifers in Groundwater Management Area 7 |
| GT13-032_TERS | 10/2/2013 | GAM task - Total Estimated Recoverable Storage | Total Estimated Recoverable Storage for aquifers in Groundwater Management Area 9 |
| GT13-033_TERS | 8/20/2013 | GAM task - Total Estimated Recoverable Storage | Total Estimated Recoverable Storage for aquifers in Groundwater Management Area 10 |
| GT13-036_TERS_Ver2 | 7/15/2013 | GAM task - Total Estimated Recoverable Storage | Total Estimated Recoverable Storage for aquifers in Groundwater Management Area 13 |
| GR13-029_MP | 11/15/2013 | GAM run - Management Plan | Management plan data for Cow Creek GCD |
| GR13-023_MP | 12/18/2013 | GAM run - Management Plan | Management plan information for Real-Edwards Conservation and Reclamation District |
| GT13-031_TERS | 1/15/2014 | GAM task - Total Estimated Recoverable Storage | Total Estimated Recoverable Storage for aquifers in Groundwater Management Area 8 |
| GT13-034_TERS | 4/2/2014 | GAM task - Total Estimated Recoverable Storage | Total Estimated Recoverable Storage for aquifers in Groundwater Management Area 11 |
| GT13-035_TERS_Ver2 | 5/16/2014 | GAM task - Total Estimated Recoverable Storage | Total Estimated Recoverable Storage for aquifers in Groundwater Management Area 12 |
| GR14-003_MP | 8/29/2014 | GAM run - Management Plan | Management plan data for Southern Trinity GCD |
| GR09-032_MP | 7/9/2010 | GAM run - Management Plan | Management plan information for Trinity-Glen Rose GCD |
| GR15-001_MP | 2/17/2015 | GAM run - Management Plan | Management plan data for Trinity Glen Rose GCD |
| GR14-015_MP | 2/9/2015 | GAM run - Management Plan | Management Plan data for Southern Trinity GCD |
| GR15-005_MP | 3/6/2015 | GAM run - Management Plan | Management plan data for Hays Trinity GCD |
| GR14-008_MP | 3/3/2015 | GAM run - Management Plan | Management plan data for Upper Trinity GCD |
| GR14-001_MP | 3/31/2015 | GAM run - Management Plan | Management plan data for Northern Trinity GCD |
| GT10-005 | 5/8/2015 | GAM task | Predictive simulations for the Trinity Aquifer in Groundwater Management Area 9 |
| GR15-002_MP | 6/30/2015 | GAM run - Management Plan | Management plan data for Medina County GCD |
| GR15-006_MP | 6/26/2015 | GAM run - Management Plan | Management Plan data for Uvalde County UWCD |
| GR15-003_MP | 11/24/2015 | GAM run - Management Plan | Management Plan data for Clearwater UWCD |
| GR16-002_MP | 4/25/2016 | GAM run - Management Plan | Management plan information for Middle Trinity GCD |
| GR16-004_MP | 5/16/2016 | GAM run - Management Plan | Management plan information for North Texas GCD |
| GR16-005_MP | 5/16/2016 | GAM run - Management Plan | Management plan information for Red River GCD |
| GR16-022_MP | 6/16/2016 | GAM run - Management Plan | Management plan data for Comal Trinity GCD |
| GR16-006_MP | 6/21/2016 | GAM run - Management Plan | Management plan information for Central Texas GCD |
| GR-_MP | 8/17/2016 | GAM run - Management Plan | Management plan information for Prairielands GCD |
| GR16-007_MP | 8/17/2016 | GAM run - Management Plan | Management plan information for Prairielands GCD |
| GR16-019_MP | 9/17/2016 | GAM run - Management Plan | Management plan information for Headwaters GCD |
| GR17-026_MP | 3/17/2017 | GAM run - Management Plan | Management plan information for Middle Trinity GCD |
| GR16-014_MP | 3/17/2017 | GAM run - Management Plan | Management plan information for Lost Pines GCD |
| GR17-004_MP | 11/29/2017 | GAM run - Management Plan | Management plan information for Bandera County RA&GD |
| GR17-009_MP | 1/30/2018 | GAM run - Management Plan | Management plan information for Hill Country UWCD |
| GR18-003_MP | 4/6/2018 | GAM run - Management Plan | Management plan information for Blanco-Pedernales GCD |
| GR19-011_MP | 2/27/2019 | GAM run - Management Plan | Management plan information for Cow Creek GCD |
| GR18-017_MP | 3/6/2019 | GAM run - Management Plan | Management plan information for Neches and Trinity Valleys GCD |
| GR19-005_MP | 3/15/2019 | GAM run - Management Plan | Management plan information for Saratoga UWCD |
| GR19-016_MP | 10/24/2019 | GAM run - Management Plan | Management plan information for Southern Trinity GCD |
| GR19-018_MP | 11/7/2019 | GAM run - Management Plan | Management plan information for Upper Trinity GCD |
| GR19-025_MP | 11/15/2019 | GAM run - Management Plan | Management plan information for Glen Rose GCD |
| GR19-027_MP | 12/13/2019 | GAM run - Management Plan | Management plan information for Southwestern Travis County GCD |
| GR19-026_MP | 1/9/2020 | GAM run - Management Plan | Management plan information for Hays Trinity GCD |
| GR20-003_MP | 8/25/2020 | GAM run - Management Plan | Management plan information for Medina County GCD |
| GR21-003_MP | 4/20/2021 | GAM run - Management Plan | Management plan information for Headwaters GCD |
| GR21-005_MP | 10/11/2021 | GAM run - Management Plan | Management plan information for Central Texas GCD |
| GR21-006_MP | 10/21/2021 | GAM run - Management Plan | Management plan information for Middle Trinity GCD |
| GR21-001_MP | 1/14/2022 | GAM run - Management Plan | Management plan information for North Texas GCD |
| GR21-002_MP | 1/24/2022 | GAM run - Management Plan | Management plan information for Red River GCD |
| GR22-007_MP | 6/28/2022 | GAM run - Management Plan | Management plan information for Post Oak Savannah GCD |
| GR22-008_MP | 8/12/2022 | GAM run - Management Plan | Management plan information for Lost Pines GCD |
| GR22-010_MP | 8/25/2022 | GAM run - Management Plan | Management plan information for Bandera County RA & GD |
| GR22-012_MP | 10/14/2022 | GAM run - Management Plan | Management plan information for Comal Trinity GCD |
| GR21-015_MAG | 4/12/2023 | GAM run - MAG | Modeled Available Groundwater for the aquifers in Groundwater Management 10 |
| GR23-017_MP | 08/30/2023 | GAM run - Management Plan | Management plan information for Blanco-Padernales GCD |
| GR23-004_MP | 05/31/2023 | GAM run - Management Plan | Management plan information for Hill Country UWCD |
| GR23-025_MP | 12/21/2023 | GAM run - Management Plan | Management plan information for Prairielands GCD |
| GR24-002_MP | 02/29/2024 | GAM run - Management Plan | Management plan information for Neches & Trinity Valleys GCD |