Research Studies
The Harris-Galveston Subsidence District conducts and sponsors research studies to explore the effects of subsidence in the Houston region. Each report provides key insights that inform the development of reasonable regulations for groundwater resources to prevent subsidence.
The GNSS survey for Harris, Galveston, and surrounding counties achieves the following goals:
- Obtain 2022 elevations for historical benchmarks that have been surveyed by the District in 1978, 1987, 1995, 2000, and some in 2007.
- Validate benchmarks within the NGS database for community use.
- Provide additional data to verify projections performed in the JRPR PRESS assessment.
The goal of this study is to assess the impact of subsidence on flood risk along Spring Creek. Study findings will provide an important perspective on the impacts of subsidence related to non-coastal flooding, the benefits of future groundwater conversion within the District, and regional groundwater management decisions.
Expected Release: Q4 2025
HGSD, in collaboration with FBSD, is working with technical experts at the Conrad Blucher Institute at Texas A&M University-Corpus Christi to develop an application for InSAR analysis as a monitoring tool. This tool will enable the tracking and detection of land surface deformation over time throughout the region. This project will involve the integration of multidisciplinary datasets for a regional and holistic approach to monitoring changes in the land surface. It is expected to be completed by summer 2026.
In alignment with the regulatory framework and associated objectives outlined in HGSD’s Science and Research Plan, and considering HGSD’s Regulatory Plan, the timely development of alternative water supplies is necessary to maintain compliance and minimize further subsidence. The District will collaborate with Carollo Engineers, Inc., Civitas Engineering Group, and Intera on a new study to assess the feasibility of developing alternative water supplies, not sourced from groundwater, in northeastern Harris County.
This study will:
- Investigate sources of alternative water
- Consider the timing of delivery
- Identify potential collaborations and partnerships
The anticipated completion date is Summer 2026.
Publications
These technical reports, produced in partnership with USGS, university research programs, and other entities, provide an in-depth analysis of the Gulf Coast aquifer and other factors that affect subsidence.
A Century (1906-2024) of Groundwater and Land Subsidence Studies in Greater Houston Region: A Review
This review highlights a century of subsidence and groundwater-level monitoring in Houston, focusing on regulations and sustainable groundwater management.
The Harris-Galveston Subsidence District (HGSD), in collaboration with several other agencies, has been operating a dense Global Navigation Satellite System (GNSS) network for subsidence and faulting monitoring within the Greater Houston region since the early 1990s. The GNSS network is designated HoustonNet, comprising approximately 250 permanent GNSS stations as of 2021. This paper documents the methods used to produce position time series, transform coordinates from the global to regional reference frames, identify outliers and steps, analyze seasonal movements, and estimate site velocities and uncertainties. The GNSS positioning methods presented in this paper achieve a 2–4 mm RMS accuracy for daily positions in the north-south and east-west directions, and 5–8 mm accuracy in the vertical direction, within the Greater Houston region.
This study, led by Dr. Zhong Lu, a professor at Southern Methodist University, is mapping subsidence from space. SMU is developing subsidence maps from 2004 to 2020 by integrating data obtained from multi-temporal Interferometric Synthetic Aperture Radar (InSAR), a remote sensing technique using data collected from orbiting satellites, to evaluate subsidence over specific periods of time across the region.
This report provides updates to the contacts between the Chicot and Evangeline aquifers; the Evangeline Aquifer and the Burkeville Confining Unit, and Burkeville Confining Unit and the Jasper Aquifer for the Gulf Coast Aquifer System developed by Young and others. The updates have been developed to support the development of the GULF 2023 model.
A stable Houston reference frame, designated Houston16, was established using publicly available GPS observations from 15 continuously operating reference stations (CORS) located outside the greater Houston area, which had more than five years of data. Houston16 will be updated every few years to mitigate degradation of the frame’s stability with time and to synchronize with future updates of the International GNSS Service (IGS) reference frame.
Timothy J. Kearns, Guoquan Wang, Michael Turco, Jennifer Welch, Vasilios Tsibanos, Hanlin Liu, Houston16: A stable geodetic reference frame for subsidence and faulting study in the Houston metropolitan area, Texas, U.S., Geodesy and Geodynamics, Volume 10, Issue 5, 2019, Pages 382-393, ISSN 1674-9847.
Aquifer storage and recovery (ASR) is a water supply strategy that utilizes an aquifer to store water underground during periods of abundant water supply and then recovers the water when it is needed. Due to the potential benefits of increasing the available water supply in the region, the HGSD sponsored this study to investigate the potential occurrence of subsidence resulting from using ASR as a water supply strategy in the Gulf Coast Aquifer System.
The U.S. Geological Survey, in cooperation with the Harris‐Galveston Subsidence District, City of Houston, Fort Bend Subsidence District, and Lone Star Groundwater Conservation District, has produced this dataset of compaction values in the Chicot and Evangeline aquifers in the Houston‐Galveston region, Texas. This dataset presents compaction values of subsurface sediments (primarily in fine-grained silt and clay layers, as compaction is minimal in sand layers) in the Chicot and Evangeline aquifers, recorded continuously using analog technology at 13 extensometers across 11 sites. These extensometers were either activated or installed between 1973 and 1980.
Ramage, J.K., and Shah, S.D., 2019, Cumulative Compaction of Subsurface Sediments in the Chicot and Evangeline Aquifers in the Houston-Galveston Region, Texas (ver. 2.0, June 2020): U.S. Geological Survey data release.
This report estimates the relative risk of subsidence associated with the development of brackish groundwater in the Jasper Aquifer of the Gulf Coast Aquifer System within the Districts. In 2015, both Harris-Galveston and Fort Bend Subsidence Districts adopted Science and Research Plans to define the strategic direction for science and research they conducted or supported. In response to interest in brackish groundwater resource development, the Districts’ respective Science and Research Plans identified that research should be performed to:
- Develop a more vertically and horizontally resolute depiction of the hydrostratigraphy of the Districts and surrounding areas; and
- Determine the occurrence and hydrogeologic characteristics of the brackish resources within the Districts and surrounding areas.
Young and others completed a report documenting the detailed hydrostratigraphy and occurrence of brackish groundwater resources within the study area in 2017. Their results provide the necessary detailed lithologic and water quality data to perform a risk assessment of brackish groundwater development in the Jasper Aquifer. The objectives of this risk assessment are to:
- Assess the potential risk of subsidence that may result from the development of brackish groundwater resources in the Jasper Aquifer within the Districts; and
- Provide the Districts with guidance on the types of activities and data that would benefit consideration as special provisions for Jasper Aquifer brackish production permits.
The District’s Annual Groundwater Reports cover four main topics: climate data, groundwater use within the District, aquifer water levels, and updated subsidence rates. Each of these topics is compared to data from previous years, providing context on how groundwater usage and the corresponding changes in water levels affect subsidence.