Aquifers play a major role in providing water to many parts of Texas. About 55 percent of all water used in the state (PDF) was sourced through aquifers in 2019. There are nine major and 22 minor aquifers that supply groundwater in Texas. Most of the water sourced from the major aquifers is used for irrigation, while others are primarily used for for municipal purposes (Exhibit 1). Aquifers are vital to the state’s economy and environment, highlighting the need for proper management and conservation of this important resource.
Exhibit 1 Water Usage Type by Major Texas Aquifers
Water Usage Type by Major Texas Aquifers
Major Aquifer
Irrigation
Municipal
Manufacturing
Livestock
Steam Electric Power
Mining
Carrizo-Wilcox
39.7%
50.7%
0.9%
2.7%
4.0%
1.9%
Edwards-Trinity (Balcones Fault Zone)
22.4%
73.3%
1.3%
0.3%
0.0%
2.5%
Edwards-Trinity (Plateau)
81.0%
14.5%
0.1%
3.8%
0.0%
0.5%
Gulf Coast
39.5%
46.8%
9.8%
2.1%
1.6%
0.2%
Hueco-Mesilla Bolson
1.5%
92.2%
4.3%
0.1%
1.6%
0.4%
Ogallala
93.6%
3.9%
0.4%
1.8%
0.2%
0.1%
Pecos Valley
75.6%
17.6%
0.0%
0.5%
0.0%
6.3%
Seymour
94.3%
5.2%
0.0%
0.5%
0.0%
0.0%
Trinity
27.3%
64.7%
2.0%
3.8%
0.0%
2.1%
Source: Texas Water Development Board
How Does an Aquifer Work?
Aquifers are underground areas made up of porous rock or sediment that hold groundwater. Water that enters an aquifer is called recharge. An aquifer can be replenished through recharge water sourced from rainfall or from surrounding streams and lakes, or through inflow from other aquifers.
Water pumped or removed from an aquifer is known as discharge. Artificial discharge occurs through manual pumping, whereas natural discharge can happen through evaporation or leakage. Aquifers can become depleted when discharge is greater than recharge or inflow. Aquifers also can experience quality degradation from human interference such as pumping.
Aquifer Preservation
Nearly 100 groundwater conservation districts (GCDs) across Texas work to protect and manage the 72 percent of aquifers in the state that fall within their service areas. GCDs maintain aquifers and their groundwater levels through a variety of tactics including minimizing over-pumping.
Over-pumping — removing more groundwater than what is entering an aquifer — is a continual challenge facing aquifer managers across the state. In Texas, groundwater is being pumped from aquifers at a rate twice that of what is sustainable, taxing the state’s groundwater supply. When water storage in an aquifer runs low or becomes empty, the ground above becomes unstable and can collapse in a process known as land subsidence. Land subsidence is concerning because it can make certain areas susceptible to flooding, sinking and water contamination. Once an aquifer collapses, its capacity to hold water is permanently reduced. Additionally, collapsed ground due to land subsidence allows contaminants to more easily enter the aquifer through the loosened soil. Restoring the quality of contaminated groundwater is time consuming and expensive to remedy.
Aquifer Storage and Recovery
Aquifer storage and recovery (ASR) is an innovative effort to preserve Texas aquifers. ASR is the process of capturing water from heavy rainfall and injecting it into underground water wells where it is stored for later use. This process can last months or sometimes years.
There are currently three ASR systems in Texas:
Fred Hervey Water Reclamation Plant, El Paso Water.
Surface Water Treatment Plant, City of Kerrville.
H2Oaks, San Antonio Water System.
El Paso Water’s Fred Hervey Water Reclamation Plant opened in 1985 and is unique in that it works as a hybrid facility. Not only does it engage in ASR, but it also uses aquifer recharge (AR) and aquifer storage, transfer and recovery (ASTR). The Hervey Plant treats 12 million gallons of wastewater daily, with a portion of the reclaimed and treated water used for aquifer storage in nearby wells and basins.
In 1989, the city of Kerrville, in conjunction with the Upper Guadalupe River Authority created its own ASR system that uses groundwater as well as surface water from the Guadalupe River. Kerrville exclusively uses wells for its ASR efforts.
The San Antonio Water System serves 2 million customers and has the largest ASR system in Texas. It is managed at SAWS’ H2Oaks Center which is also home to water production from the Carrizo-Wilcox aquifer, a desalination center, 12 water production wells, two injection wells, a water testing facility and a treatment processing area. An estimated 200,000 acre-feet of water is stored in Carrizo-Wilcox through ASR.
ASR is a beneficial tool for water preservation, but not all aquifers can use it. Water in the Edwards Aquifer, one of the biggest aquifers in the region, moves too quickly through the aquifer’s limestone to implement ASR. The Edwards Aquifer Authority (EAA), the GCD that protects the Edwards Aquifer, is exploring other possible methods of ASR including storing water deeper within the aquifer. EAA believes that ASR can help diversify water usage within the Central Texas region.
Aquifer Funding
Funding for the state’s aquifers, similar to other water conservation efforts, comes from various state and federal funds and private funds.
In July 2022, the non-profit organization Texas Water Trade created the Aquifer Resilience Fund, which uses $12.75 million from Texas Water Development Board and other organizations to provide landowners with water conservation resources that reduce strain on local aquifers. GCDs also receive grant and loan funding to support groundwater and aquifer preservation through programs like the Groundwater Conservation District Loan Program, supported by the Texas Water Development Board. Many GCDs receive funding from local organizations seeking to support their local aquifers.
Major Aquifers in Texas
Exhibit 2 Major Aquifer Map
CARRIZO-WILCOX
EDWARDS-TRINITY (BALCONES FAULT ZONE)
EDWARDS-TRINITY (PLATEAU)
GULF COAST
HUECO-MESILLA BOLSON
OGALLALA
PECOS VALLEY
SEYMOUR
TRINITY
Source: Texas Almanac
Carrizo-Wilcox
The Carrizo-Wilcox Aquifer is located beneath 66 counties in the northeast region of the Rio Grande Valley in South Texas to Arkansas and Louisiana. Irrigation accounts for more than half of the aquifer’s discharge. Water levels in several counties in this region are very low due to over-pumping.
Edwards(Balcones Fault Zone) (San Antonio-oriented)
The Edwards Aquifer is located beneath 13 counties stretching from Kinney County, through Northeast San Antonio, to Bell County. Municipal use accounted for 72 percent of the aquifer’s discharge. The Edwards Aquifer is the primary water source for San Antonio, the seventh-largest city in the U.S.
Edwards-Trinity(Austin-oriented)
The Edwards-Trinity Aquifer is located beneath 40 counties stretching from the Hill Country to the West Texas Trans-Pecos region outside of El Paso. Irrigation accounted for 79 percent of aquifer discharge in the Northwestern region, causing low water levels in Glasscock and Reagan counties. In other areas, the aquifer supplies fresh water for municipal and livestock use.
Gulf Coast
The Gulf Coast Aquifer is located along the Texas coastline across 54 counties, ranging from the Rio Grande Valley to the Louisiana border. It is divided into three water-producing smaller aquifers known as Chicot, Evangeline and Jasper. Municipal use accounted for 62 percent of total aquifer discharge.
Over-pumping has caused a decline in water levels in the southwest portion of the aquifer region, resulting in land-surface subsidence in the Galveston area that can lead to sinking of existing infrastructure and flooding.
Hueco-Mesilla Bolson
The Hueco-Mesilla Bolson Aquifer is located beneath El Paso and Hudspeth counties in West Texas. It serves as a municipal water source for both El Paso and Ciudad Juarez. Municipal use accounted for 90 percent of aquifer discharge. Large water withdrawals from the cities of El Paso and Ciudad Juarez have caused significant declines in water levels and water quality.
Ogallala
Located beneath 48 counties in the Texas Panhandle, the Ogallala Aquifer not only covers a large portion of Texas but also seven other states, from Texas to South Dakota. The aquifer covers 175,000 square miles, making it the largest aquifer in the U.S. In 2019, more than 4.4 million acre-feet were pumped from the Ogallala Aquifer, accounting for 67 percent of water pumped from the major aquifers. More than 90 percent of the water pumped was used for irrigation.
The Pecos Valley Aquifer is located beneath 12 counties in Pecos River Valley in West Texas. Irrigation accounts for 80 percent of aquifer discharge. Water levels vary throughout the region. Levels in Ward County continue to decline due to over-pumping, while other counties such as Reeves and Pecos have experienced less strain.
Seymour
The Seymour Aquifer is located beneath 25 counties in the Northwest and Panhandle regions. Irrigation makes up more than 90 percent of aquifer discharge. Water types range from fresh to saline. Saline water has increased over the years due to pumping in the area that has led to concerns over potable water quality.
Trinity
The Trinity Aquifer is located beneath 61 countries from Red River in North Texas to the Hill Country in Central Texas. Municipal use makes up 63 percent of aquifer discharge. Over-pumping has resulted in water level declines in the Dallas-Fort Worth area, ranging from losses of 350 feet to more than 1,000 feet.
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