Environmental Stewardship Celebrates a Water Achievement in the Central Texas

Groundwater Availability Model improvements will include groundwater-surface water integration for the Colorado River and the Central Carrizo-Wilcox Aquifer


GAM predicted impacts of planned Simsboro pumping. Click here for more information

UPDATE (11/22/17)

On Thursday July, 21, 2016, the Texas Water Development Board (TWDB) authorized the Executive Director to negotiate and execute eight contracts in a total amount not to exceed $745,000 for environmental flow studies in the Brazos, Colorado and Lavaca, and Nueces basins.  These improvements to the GMA-12 Groundwater Availability Model are now near completion, however, we are awaiting release of the final report on the CL-BBASC portion of the report that was due September 1, 2017.

The GMA-12 Groundwater Availability Model (GAM) Improvements project was one of the studies included for contracting. This authorization completes authorization for 27 projects totally $2 million in funding for environmental flow studies across the state. Once completed, this project will provide a robust groundwater-surface water interaction model for predicting and managing the Simsboro and other aquifers in GMA-12. See below for background and more details.


After seven years of advocating for action on groundwater-surface water interaction  issues in Central Texas, we are on the verge of a major step forward in our efforts to protect the Colorado River and its tributaries from over-pumping of groundwater.   A recent contract between the Texas Water Development Board (TWDB) and INTERA Incorporated will play a vital step in helping planners understand and manage this important ecological and hydrological relationship, thereby achieving one of our major goals – to establishing a science link between groundwater and surface water to inform policy and management decisions.

Conservation Districts (GCDs) in Groundwater gma_12Management Area 12 (GMA-12), recognizing weaknesses in the capability of the groundwater model used to guide their management decisions, raised over $100,000 to make improvements in the model’s ability to predict groundwater-surface water interactions that result form groundwater pumping. Both the Lower Colorado River Authority (LCRA) and the Brazos River Authority (BRA) provided $20,000 each in additional funding for the project.

Environmental Stewardship, working through the Colorado-Lavaca Bay and Basin Area Stakeholder Committee (CL-BBASC), was able to raise an additional $60,000 to enhance the model still further and develop a monitoring plan (See bulletin for details). These improvements, when combined with other improvements funded by the TWDB, will provide a Groundwater Availability Model (GAM) for the Central Carrizo-Wilcox and associated aquifers that will enable better modeling of the relationship between the Colorado River and the aquifers that provide groundwater base-flow to the river as it flows through Bastrop and Fayette counties. INTERA won the contract to make the necessary improvements to the GMA-12 GAM and the completed GAM is expected to be available in April, 2018 (See final report below).   In addition, the CL-BBASC requested SB3 funding in 2017 for initial data gathering to implement groundwater-surface water interaction field work resulting from the GAM improvements study (see below).

INTERA’s RFQ Proposal. 

ES Review of Draft Report

INTERA’s Final Report (file too big to upload (18.3 MB) – Email ES to request

CL-BBASC Request for SB3 Funding for Field Studies: 

Initial Data Gathering To Implement Groundwater-Surface Water
Interaction Field Work From GAM Improvements Study

This is an important achievement for three reasons:

1) The GAM improvements will provide a platform for quantifying the relationship between the Colorado River and the Carrizo-Wilcox aquifer group (which included the Simsboro) on a localized basis;

2) an initial monitoring plan will be developed that, if implemented, will enable the monitoring of the relationship between the Colorado River and other aquifers up and down the basin; and finally,

3) it furthers a dialogue between the entities responsible for managing the river and groundwater resources in the basin.

The GMA-12 GAM Improvement Project is scheduled to be completed in late 2017 or early 2018 and will be available in time to be used in the next round of review for the GMA-12 desired future conditions.

Click her for more information on the technical aspects.