Groundwater Models

Groundwater Availability Models

Alternative Groundwater Flow Models

Groundwater, along with surface water, is important for maintaining the viability of the state's natural resources, health, and economic development. The projected doubling of the state's population by the year 2060, coupled with the constant threat of drought, makes it imperative that Texas develop effective plans to meet future water needs. Effective planning, however, requires accurate assessments of the availability of water, and assessing the availability of groundwater is often much more difficult than assessing that of surface water.

Groundwater is difficult to observe and measure because it resides below the land surface and responds to rainfall much more slowly than rivers and lakes do. Aquifer systems are complex due to flows into and out of the aquifer, the interaction between surface water and groundwater, and the uncertainty of aquifer properties.

Because of this complexity, computer models are excellent tools for assessing the effect of pumping and droughts on groundwater availability. Groundwater availability modeling is the process of developing and using computer programs to estimate future trends in the amount of water available in an aquifer and is based on hydrogeologic principles, actual aquifer measurements, and stakeholder guidance.

What information does a groundwater availability model include?

Groundwater availability models include comprehensive information on each aquifer, such as recharge (amount of water entering the aquifer); geology and how that conveys into the framework of the model; rivers, lakes, and springs; water levels; aquifer properties; and pumping. Each model is calibrated to ensure that the models can reasonably reproduce past water levels and groundwater flows.

How are the models being used?

Completed models have already proven valuable to water planning. Texas law requires groundwater conservation districts and regional water planning groups to use estimates of modeled available groundwater, based on the desired future conditions of aquifers determined for the 16 groundwater management areas, in their management and regional water plans. Groundwater availability models have been and will continue to be used to estimate the modeled available groundwater for each aquifer for each groundwater conservation district, as appropriate and applicable.

Groundwater conservation districts may request a GAM update if new data are significant enough to potentially affect joint groundwater planning and groundwater management decisions. The Guidance Document below provides the requirements and process for requesting an update to the official, regional GAMs developed or maintained by the TWDB Groundwater Modeling Department.

Guidance for Requesting a Groundwater Availability Model Update based on New Data

Where may I get more information?

Please contact Groundwater Modeling Department (or 512-475-0470) for more information.