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.

Soliciting Stakeholder Ideas for Research Projects to Support Groundwater Modeling

Submission Deadline for FY24-25: Closed

The Texas Water Development Board (TWDB) solicits ideas for research projects to support groundwater modeling in the state of Texas. Although the deadline for FY24-25 funding ideas has closed, the Groundwater Modeling (GM) Department welcomes ideas that could be used for future projects. The intent of this TWDB solicitation is to provide stakeholders the opportunity to provide the GM Department with potential research projects ideas utilizing the GM research budget.

Proposed research ideas may be for new projects that support groundwater model development or ideas that build upon previous research projects from the GM Department. By soliciting ideas from stakeholders, we aim to have a more thorough view of projects that could benefit our stakeholders and provide a greater understanding of Texas groundwater resources.

Every biennium, the TWDB receives appropriations from the Texas Legislature to use for research related to groundwater modeling and to support groundwater availability model development. This funding becomes available in September 2023 and every odd-numbered year thereafter. In August 2023, the GM Department will review submitted project ideas alongside internal research ideas. The research ideas will be evaluated according to the rubric below and the Groundwater Division will select projects that align to the GM Department goals and can be completed with available budget. The submitted project ideas and rubric scores will posted publicly on this webpage.

The main goals of the Groundwater Modeling (GM) Department are to:

  1. Develop and maintain models for the major and minor aquifers of Texas.
  2. Conduct groundwater availability model runs and develop reports to support groundwater conservation districts, groundwater management areas, regional water planning groups, and the legislature. These model runs are limited to water budget information for groundwater management plans, modeled available groundwater estimates based on desired future conditions, and special requests from the legislature.
  3. Provide technical support for petitions to appeal desired future conditions.
  4. Fund and oversee external contracts to develop supporting data, develop new models, and/or update existing models.

Please use the links below to download the scoring rubric and access the idea solicitation form. Please contact Daryn Hardwick, Groundwater Modeling Manager, at with any questions.

Link to Submission Form

Download the Scoring Rubric