Northern portion of the Gulf Coast Aquifer System Groundwater Availability Model (GAM)
In October 2019, the US Geological Survey in cooperation with the Harris-Galveston Subsidence District and the Fort Bend Subsidence District began updating the groundwater flow model for the northern portion of the Gulf Coast Aquifer System. The TWDB and the Harris-Galveston Subsidence District signed a letter of agreement that once the model and other deliverables satisfy the technical standards and procedural requirements of the TWDB GAM Program, the model, report, and source data will replace the Houston Area Groundwater Model (HAGM) as the GAM for the area. The model, known as the GULF-2023 model, was completed and released in February 2024.
Draft Recalibrated Model
The draft groundwater availability model (GAM) for the northern portion of the Gulf Coast Aquifer System is currently under public review. The deadline to submit comments to the TWDB is end of day on June 25, 2025.
Please send any comments to gam@twdb.texas.gov.
- Draft Recalibrated Model Report: Groundwater Availability Model for the northern portion of the Gulf Coast Aquifer System (Version 4.1)
- Appendices: Groundwater Availability Model for the northern portion of the Gulf Coast Aquifer System (Version 4.1)
| Draft Model Files |
|---|
| Model Files (44MB zipped) |
| Draft Ancillary Data |
|---|
| Ancillary Data (11MB zipped) |
Model Report
- "Hydrogeology, Land-Surface Subsidence, and Documentation of the Gulf Coast Land Subsidence and Groundwater-Flow (GULF) Model, Southeast Texas, 1897–2018" | USGS ISSN: 2330-7102 (external link)
- "Appendix A Stakeholder Comments" | Stakeholder comments received by the TWDB and responses.
Model Files and Associated Data
Please see the GAM files download page for the current model files and associated data.
Aquifer data is only available as a package for the entire model area and requires GIS software for processing. Please see the GAM files download page for aquifer data.
Joint Regulatory Plan Review Meetings (JRPR)
| ID | Date | Location |
|---|---|---|
| JRPR-1 | 05/20/2020 | Online meeting; click at left for meeting video and other materials. You will be leaving the TWDB website. |
| JRPR-2 | 09/30/2020 | Online meeting; click at left for meeting video and other materials. You will be leaving the TWDB website. |
| JRPR-3 | 12/10/2021 | Online meeting; click at left for meeting video and other materials. You will be leaving the TWDB website. |
| JRPR-4 | 06/08/2021 | Online meeting; click at left for meeting video and other materials. You will be leaving the TWDB website. |
| JRPR-5 | 12/14/2021 | Online meeting; click at left for meeting video and other materials. You will be leaving the TWDB website. |
Model Report
- "USGS Houston Area Groundwater Model (Version 1.1)" | USGS SIR 2012-5154.
- "Hydrogeology and Simulation of Ground-Water Flow and Land-Surface Subsidence in the Northern Part of the Gulf Coast Aquifer System, Texas." | USGS SIR 2004-5102.
- "Evaluation of Ground-Water Flow and Land-Surface Subsidence Caused by Hypothetical Withdrawals in the Northern Part of the Gulf Coast Aquifer System, Texas." | USGS SIR 2005-5024.
- Review comments for USGS SIR 2005-5024.
Other Reports
"Estimation of Groundwater Recharge to the Gulf Coast Aquifer in Texas, USA."
Stakeholder Advisory Forums (SAF)
Send us an email if you would like to receive SAF notifications.
| ID | Date | Location |
|---|---|---|
| SAF 8 | 2/17/2004 | Friendswood, Texas - Harris-Galveston Coastal Subsidence District (1660 West Bay Area Blvd) |
| SAF 7 | 7/24/2003 | Friendswood, Texas - Harris-Galveston Coastal Subsidence District (1660 West Bay Area Blvd) |
| SAF 6 | 4/24/2003 | Friendswood, Texas - Harris-Galveston Coastal Subsidence District (1660 West Bay Area Blvd) |
| SAF 5 | 1/29/2003 | Friendswood, Texas - Harris-Galveston Coastal Subsidence District (1660 West Bay Area Blvd) |
| SAF 4 | 6/5/2002 | Friendswood, Texas - Harris-Galveston Coastal Subsidence District (1660 West Bay Area Blvd) |
| SAF 3 | 11/15/2001 | Friendswood, Texas - Harris-Galveston Coastal Subsidence District (1660 West Bay Area Blvd) |
| SAF 2 | 8/2/2001 | Friendswood, Texas - Harris-Galveston Coastal Subsidence District (1660 West Bay Area Blvd) |
| SAF 1 | 5/2/2001 | Friendswood, Texas - Harris-Galveston Coastal Subsidence District (1660 West Bay Area Blvd) |
Other Resources
Please see the Gulf Coast Aquifer System and the Research Projects in Support of Groundwater Models pages for other reports and publications.
For model runs see the GMA 14 page.