Measuring Groundwater in Texas March 2015

Understanding groundwater is critical when discussing water in Texas. Groundwater and surface water supply most of Texas' water, and the Texas Water Development Board (TWDB) studies both to support the water planning process with as much scientific background as possible.

The TWDB's goal in studying groundwater is to help Texans know and understand their water resources and to provide information to help Texas manage its current and future water supply. By monitoring groundwater levels, observing trends in groundwater quality, and using tools to predict future changes in groundwater, the TWDB helps regional water planning groups, local groundwater conservation districts, and other decision makers develop their water resources responsibly and with reliable data.

Groundwater is generally defined as any water beneath the surface of the land. The vast majority of groundwater occurs in aquifers, which are naturally formed, underground layers of rock, sand, and gravel that collect and transmit water that seeps below the ground. Alternatively, surface water is water at the surface, in bodies of water such as streams, rivers, lakes, and reservoirs.

"Groundwater accounts for about 60 percent of all water use in Texas, so it is a major source of Texas' water supply," said Larry French, Director of Groundwater Resources at the TWDB. "The Texas Water Development Board is responsible for the majority of county and regional groundwater studies in the state, which include a variety of scientific tasks designed to capture short- and long-term information about the status of the state’s groundwater supply."

There are 9 major and 21 minor aquifers in Texas that the TWDB studies. Major aquifers produce large amounts of water over large areas – a well-known example being the Ogallala Aquifer that stretches underneath the high plains and extends through eight other states north of Texas. Minor aquifers, on the other hand, are categorized by either producing small amounts of water over large areas or large amounts of water over small areas.

Groundwater is critical to Texas. Cities and agriculture alike rely on groundwater, but 79 percent of it is used for irrigation, making groundwater especially essential for agriculture. Nonetheless, 38 percent of water used by municipalities is sourced from groundwater. The TWDB monitors the quantity and quality of water in the state's aquifers to ensure that Texans know how much groundwater is available for future use.

The TWDB monitors daily water levels through automatic recorder wells at more than 180 locations in Texas. It also measures nearly 2,000 wells annually and receives water levels in an additional 5,500 wells measured by cooperators. Each year the TWDB also collects hundreds of groundwater samples from regional aquifers for chemical analysis. This variation of monitoring approaches allows the TWDB to not only provide current, real-time updates, but also a more thorough analysis of trends shaping the quantity and quality of the groundwater in Texas.

As part of its groundwater research, the TWDB also develops groundwater availability models for the state's aquifers. These models are computer-based tools that can predict the future amount of water available from an aquifer based on several variables. The TWDB creates these models for regional use so that local groundwater conservation districts, planning groups, and others can use the information to forecast the future water supply in a specific area.

These efforts to understand groundwater, which can be seen in many different scientific tasks being performed across the state, are meant to be shared with the public. The TWDB makes data accessible to Texans by providing readings from water wells, maps outlining aquifers, all of its reports, groundwater quality information, and much more on the TWDB website. Because of their size, the groundwater availability models are available by request.

The mission of the TWDB is to develop affordable and sustainable water for Texas. Part of that is accomplished by measuring groundwater, but another part is by making sure Texans can see each step we take. Please join in our efforts to plan for the future by learning more about our water resources in Texas.

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