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The details for the updated model are part of a new U.S. Geological Survey report published on January 13. The model simulates the northern part of the Gulf Coast Aquifer of Texas and incorporates the latest data on groundwater and land subsidence–a decrease in the land surface–to provide a variety of simulated groundwater flow and land subsidence estimates from 1897 through 2018. Subsidence has been a growing concern in the area for decades because it can increase the risk of flooding over time and contribute to infrastructure damage.

The new USGS model, developed in collaboration with the Harris-Galveston and Fort Bend Subsidence Districts and the Texas Water Development Board, reflects changes in recent years to the distribution of groundwater withdrawals as well as more recent climate conditions and is expected to be used as a Groundwater Availability Model for the Texas Water Development Board’s groundwater availability modeling program for this area.

“The model incorporates the latest in uncertainty quantification methods to produce a range of subsidence and water level change estimates that can be used by decision makers to address future groundwater availability issues.” said John Ellis, the report’s author and a Supervisory Hydrologist with the USGS Oklahoma-Texas Water Science Center. “In addition to including information about the groundwater-flow model, this report also provides important long-term trends in water resources for the greater Houston area and northern Texas Gulf Coast.”

The report extensively describes groundwater development, groundwater levels, recharge and groundwater flow, and subsidence trends in the area from about 1897 to 2018. Various compaction and subsidence measurement techniques were integrated with groundwater-level data to provide a better understanding of aquifer-system response to declining groundwater levels and the subsequent recovery.

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The report also examines more recent subsidence in northern and western Harris County and in Montgomery County using multiple methods. The model was also used to estimate compaction in each aquifer with a focus on the geologic units that contain the Jasper aquifer at selected benchmarks in northern Harris County and Montgomery County.

Some of the findings from the report include:

1. There is a well-established connection between long-term subsidence rates and groundwater-level declines in the greater Houston area.
2. Land subsidence in Spring, The Woodlands, and Conroe through 2021 was approximately 4.2 feet, 2.5 feet, and 1.5 feet, respectively—most of which has occurred since 1987.
3. Simulated Jasper aquifer compaction in Spring, The Woodlands, and Conroe accounts for about 16 percent, 33 percent, and 57 percent of subsidence, respectively.
4. Subsidence often continues at a reduced rate when groundwater levels remain at or near historical minimum levels.
5. The earliest subsidence in the area began prior to 1918 in downtown Houston and shortly after in the Goose Creek oil field.

The report entitled “Hydrogeology, Land-Surface Subsidence and Documentation of the Gulf Coast Land Subsidence and Groundwater-Flow Model, Southeast Texas, 1897­–2018” and the companion data release can be found here and here.

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