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 reasonable regulations of groundwater resources to prevent subsidence.

Monitoring the Land Surface from Space

HGSD, in cooperation with FBSD, is collaborating 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 that will allow for 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 of the land surface. It will be completed in the summer of 2026.  

Click here for more information.

Evaluation of Subsidence Impacts on Spring Creek Watershed (2020-2022)

The goal of the study is to evaluate how subsidence impacts flood risk along Spring Creek. Study findings will provide an important perspective on subsidence impacts related to non-coastal flooding, the benefits of future groundwater conversion within the District, and regional groundwater management decisions.

Click here for more information

GNSS Survey for Harris, Galveston, and Surrounding Counties

A new GNSS survey for Harris, Galveston, and surrounding counties is available here.

With this survey, we are excited to achieve the following goals:

1. Obtain 2022 elevations for historical benchmarks that have been surveyed by the District in 1978, 1987, 1995, 2000, and some in 2007.
2. Validate benchmarks within the NGS database for community use.
3. Provide additional data to verify projections performed in the JRPR PRESS assessment.

Click here for more information and 2022 GNSS Survey results.

View the 2022 GNSS Survey Map here!

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.

Houston GNSS Network for Subsidence and Faulting Monitoring: Data Analysis Methods and Products (2022)

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 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.

Click here for the full report.

Mapping Land Deformation over Houston-Galveston Using Multi-temporal InSAR Processing (2020-2021)

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.

Click here to read the report

HGSD-FBSD-Burkeville-Report-2020-e1622566363607-COVER

The Delineation of the Burkeville Confining Unit and the Base of the Chicot Aquifer to Support the Development of the Gulf 2023 Groundwater Model (2020)

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.

Full Report

HOUSTON16: A Stable Geodetic Reference Frame for Subsidence and Faulting Study in the Houston Metropolitan Area, Texas, U.S. (2019)

A stable Houston reference frame, designated Houston16, was established using publicly available GPS observations at stations with more than five years of data from 15 continuously operating reference stations (CORS) located outside of the greater Houston area. 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, https://doi.org/10.1016/j.geog.2018.05.005

Assessment of Subsidence and Regulatory Considerations for Aquifer Storage and Recovery in the Evangeline and Chicot Aquifers (2019)

Aquifer storage and recovery (ASR) is a water supply strategy that uses an aquifer to store water underground during times when water is plentiful and then recover the water when it is needed. Because of the potential benefits of increasing the available water supply in the region, the HGSD sponsored this study to research the potential occurrence of subsidence from using ASR as a water supply strategy in the Gulf Coast Aquifer System.

Full Report

Cumulative Compaction of Subsidence Sediments (2019) in Thirteen Extensometers Completed in the Chicot and Evangeline Aquifers in the Houston-Galveston Region, Texas

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 shows compaction values of subsurface sediments (mostly in the fine-grained silt and clay layers because little compaction occurs in sand layers) in the Chicot and Evangeline aquifers that were recorded continuously by using analog technology at the 13 extensometers at 11 sites that 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, https://doi.org/10.5066/P9YGUE2V.

Investigation of the Brackish Groundwater Resources in the Gulf Coast Aquifer and the Determination of Potential Subsidence Risk Due Resources Development (2018)

Report on the Delineation of Fresh, Brackish and Saline Groundwater Resources Based on Interpretation of Geophysical Logs (2018)

Subsidence Risk Assessment and Regulatory Considerations for the Brackish Jasper Aquifer (2018)

Cumulative Compaction of Subsidence Sediments in Thirteen Extensometers Completed in the Chicot and Evangeline Aquifers in the Houston-Galveston Region, Texas (2015)

Region Groundwater Update Project – Final Report (2013)

Annual Groundwater Reports

The District’s yearly report covers 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.