To prevent further subsidence in Harris and Galveston counties, the Harris-Galveston Subsidence District provides groundwater regulation backed by the best available science. This adaptive management strategy, known as the Regulatory Plan, divides HGSD’s jurisdiction into three regulatory areas. These areas all share the goal of preventing subsidence by reducing overall groundwater withdrawals; however, each regulatory area’s groundwater withdrawals will be reduced to a specific percentage of its total water demand by a designated date, based on the availability of alternative water sources, geophysical characteristics, and groundwater demand. The District periodically reviews its regulatory plan to ensure that predictions of future water needs and subsidence are up to date and to confirm that the plan ultimately ceases subsidence in Harris and Galveston counties.
The District completed its latest Joint Regulatory Plan Review in 2025, in cooperation with the Fort Bend Subsidence District, to estimate future changes in population and water demand, assess the availability of alternative water supplies, review and update predictive subsidence models, and evaluate planned regulatory requirements for future subsidence rates. The results of this review are published below.
TASK A – Population & Water Demand Projections
This task will provide estimated population and water supply needs for Austin, Brazoria, Chambers, Fort Bend, Galveston, Harris, Liberty, Montgomery, Waller, Wharton counties. This analysis will be grounded with the latest 2020 census data and will develop updated population and water demand projections through 2100. Population estimates are being coordinated with the Texas Water Development Board so that they can be adapted for the 2026 Region H Water Plan.
TASK B – Alternative Water Supply Assessment
The District’s mission to prevent future subsidence is achieved by reducing reliance on groundwater through the use of alternative water supplies (water resources that, when developed, do not contribute to subsidence – in our area, our primary alternative water source is treated surface water.) This task examines the availability of additional alternative water supplies and advanced water development methods, including frontier resources such as seawater desalination and reclaimed water supply.
TASK C – Land Subsidence & Groundwater Flow Models
The District has historically used an analytical computer model to predict land subsidence caused by pumpage of groundwater, also known as the PRESS (Predictions Relating Effective Stress and Subsidence) model. The PRESS model was adapted for use by the Harris-Galveston Subsidence District in 1978. The PRESS models are legacy models in the District that are focused at 26 specific locations throughout Harris, Galveston, and Fort Bend counties. For this study, the 26 PRESS models used in the 2013 Regulatory Plan Update will be updated with current data (through 2020) to determine if they will require recalibration for use in the Joint Regulatory Plan Review. Additionally, the use of the new technology within the GULF-2023 model is being evaluated as a potential replacement for the PRESS models.
The District worked with the U. S. Geological Survey (USGS) and the Texas Water Development Board to develop the Gulf Coast Land Subsidence and Groundwater Flow (GULF)-2023 model. The GULF-2023 model simulates the impacts of groundwater use on aquifer water levels and land subsidence. The model area extends from Washington County to Newton County and was developed as a regional tool for planning efforts related to the Groundwater Management Area 14, in addition to the Joint Regulatory Plan Review.
TASK D – Regulatory Scenarios
Initially, a “post-audit” of the groundwater flow and subsidence model used for the 2013 Regulatory Plan Update will be conducted. Utilizing the information gained from the post-audit, a number of regulatory scenarios are used to examine variables that are likely to drive regulatory decision-making, such as conversion timelines, regulatory boundaries, drought impacts, use of groundwater credits, and impacts of groundwater regulation (or lack thereof) in adjacent counties.
For More Information
For more information about the Joint Regulatory Plan Review, click here to contact us. You can also join the regulatory review mailing list here to be notified about upcoming meetings for the Joint Regulatory Plan Review.