The Harris-Galveston Subsidence District (District) controls subsidence within the District by regulating the use of groundwater based on the District’s Regulatory Plan. The Plan is based on many factors including expected population growth and migration and the availability of alternative source waters. The District periodically reviews our regulatory plan to assure that the 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. Both the regulatory plan review and Regional Groundwater Update Project (RGUP) were completed in 2013 in partnership with the Fort Bend Subsidence District and the Lone Star Groundwater Conservation District.
The District initiated a Joint Regulatory Plan Review in January 2020 in cooperation with the Fort Bend Subsidence District to estimate future changes in population and water demand, assess the availability of future alternative water supplies, review and update predictive subsidence models, and evaluate planned regulatory requirements on future subsidence rates. The Joint Review will be complete in 2024, and its results will be used as the basis for any future District Regulatory Plan modifications.
1. 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.
2. 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.
3. 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 is being developed as a regional tool for planning efforts related to the Groundwater Management Area 14 in addition to the Joint Regulatory Plan Review.
4. 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.