HGSD Issues Final 2025 Report on Groundwater, Subsidence

6/23/26 – In May of this year, I posted a PowerPoint from the Harris-Galveston Subsidence District showing a preview of their 2025 annual groundwater report. The final report has since been published. You can follow the links below to its component parts:

• Two-page overview/info sheet – explains at a high level how drought, population growth, and regulation interact to influence groundwater use and subsidence
• An updated interactive subsidence map showing representative locations throughout the region
• The PowerPoint presentation discussed in May
• A 43-minute video of the PowerPoint being presented to a public gathering (including Q&A and public comments)
• A 6-page executive summary of the report
• The full 275-page report with appendices.

The people at the Subsidence District are real scientists. Anyone interested in earth sciences will find this material enlightening. It could even make a great summer science project for your students.

Report Shows Impact of Regulation in Reducing Subsidence

By comparing groundwater reports from previous years, you can see how subsidence has shifted in reponse to regulations. The earliest-regulated areas have minimized subsidence, while it still rages in areas only recently regulated.

Two centimeters is a little less than an inch. So in a decade, those areas with maroon shading could sink 8-12 inches.

But downstream areas are sinking less. Far less. That’s called differential subsidence. And differential subsidence can reduce the elevation of one area relative to others nearby.

Impacts of Subsidence on Infrastructure, Property Values

For instance, the Lake Houston Dam is sinking at a much slower rate than areas upstream in Montgomery County. That, in essence, tilts the lake toward its headwaters, reducing the safety margin that people built their homes above the floodplain.

But even before you flood, you could experience subsidence as cracks in concrete or in the walls of your home. Subsidence can even trigger geologic faulting.

Combatting Subsidence

Combatting subsidence requires reducing groundwater usage. Said another way, it requires getting on surface water. That’s why the City has spent $2 billion to quintuple the treated surface water supply from Lake Houston.

The North Harris County Regional Water Authority is also constructing an additional 94 miles of transmission and distribution lines to connect 45 Municipal Utility Districts and get them off groundwater.

That’s how serious subsidence is.

Posted by Bob Rehak on 6/23/2026

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