LAND SUBSIDENCE

Houston land subsidence and the Gulf Coast aquifer: causes, history and groundwater rules

Why the Houston–Galveston region sank as much as 9 feet, how pumping the Gulf Coast aquifer causes permanent subsidence, and how subsidence districts now limit groundwater use.

By Argos Tellus · Updated October 2, 2026

KEY TAKEAWAYS

Heavy groundwater pumping from the Gulf Coast aquifer system caused parts of the Houston–Galveston region to sink by as much as 9 feet; the first subsidence was recorded near Baytown in 1918 (Harris-Galveston Subsidence District).
Subsidence happens when falling water pressure lets clay layers in the aquifer compact. Most of that compaction is permanent, and it raises flood risk on a low-lying coast.
In 1975 the Texas Legislature created the Harris-Galveston Subsidence District (HGSD) — the first district of its kind in the U.S. — to regulate groundwater withdrawals and stop subsidence.
After HGSD’s first regulatory plan in 1976, Ship Channel industries converted to surface water from Lake Livingston, and subsidence in the Baytown–Pasadena area was largely halted.
HGSD’s regulatory plan requires permittees under certified groundwater reduction plans to limit groundwater to no more than 20% of total water demand beginning with 2035 permits.

How groundwater pumping makes land sink

The Gulf Coast aquifer system beneath Houston is a thick sequence of sands interbedded with clays. When wells pump water from the sands, water pressure falls; water then drains slowly out of the clay layers, which compact like a squeezed sponge. The land surface sinks with them.

Sand layers rebound somewhat when water levels recover, but compacted clay largely does not. That is why subsidence is mostly permanent — and why stopping it requires keeping water levels from falling further, not just waiting for recovery (see groundwater depletion).

How much Houston sank

Groundwater use grew rapidly with the region’s petrochemical industry and population in the 20th century, producing hundreds of feet of water-level decline in the Gulf Coast aquifer system. The first recorded subsidence was near Baytown in 1918, and some areas sank more than 9 feet within four decades.

The consequences were most visible along Galveston Bay. Low-lying neighborhoods in the Baytown–Pasadena area sank toward or below sea level; Baytown’s Brownwood subdivision, repeatedly flooded, was abandoned after Hurricane Alicia in 1983 and is now a nature center. Subsidence also damaged wells, pipelines and drainage, and it permanently increased flood exposure across much of the region.

Subsidence districts and the shift to surface water

The Texas Legislature created the Harris-Galveston Subsidence District in 1975 as the first entity in the U.S. with authority to restrict groundwater withdrawals specifically to prevent subsidence. The neighboring Fort Bend Subsidence District followed in 1989.

HGSD’s first regulatory plan in 1976 pushed industries on the Houston Ship Channel to switch to surface water from the newly completed Lake Livingston. Subsidence in the Baytown–Pasadena area slowed dramatically and has since been largely halted. Later plans divided the district into regulatory areas with staged reduction targets, and regional water authorities built pipelines to deliver surface water to suburbs that had relied on wells.

The 2035 groundwater reduction target

Under HGSD’s regulatory plan, permittees operating under a certified groundwater reduction plan must reduce and keep groundwater withdrawals to no more than 20% of their annual total water demand beginning with permits issued in 2035. Large users in the region therefore plan around surface water or alternative supplies, with groundwater as a limited, regulated share.

For new industrial and commercial projects — including large data centers — that means the question in greater Houston is less “is there groundwater?” than “what share can we permit, and what surface or reclaimed supply covers the rest?” Outside the subsidence districts, local groundwater conservation districts set the rules.

Frequently asked questions

Why is Houston sinking?

Mainly because of decades of groundwater pumping from the Gulf Coast aquifer system. As water pressure fell, clay layers in the aquifer compacted and the land surface sank — by as much as 9 feet in parts of the Houston–Galveston region.

Is Houston subsidence permanent?

Largely, yes. Compacted clay does not rebound meaningfully when water levels recover, so lost elevation is not regained. Regulation aims to prevent further subsidence by limiting groundwater withdrawals.

What is the Harris-Galveston Subsidence District?

A special-purpose district created by the Texas Legislature in 1975 to regulate groundwater withdrawals in Harris and Galveston counties to end subsidence — the first district of its kind in the U.S.

How much groundwater can Houston-area users pump?

Under the HGSD regulatory plan, permittees under certified groundwater reduction plans must limit groundwater to no more than 20% of their total annual water demand beginning with 2035 permits. Requirements vary by regulatory area and district.

HOW ARGOS HELPS

Phreatic — groundwater availability

A dedicated Gulf Coast aquifer model among its per-aquifer forecasters, with water-level and drawdown projections.

CARI — aquifer reasoning agent

Ask about groundwater limits and subsidence-district rules for a Houston-area site.

SOURCES

Figures are taken from the primary sources above and dated as of the update shown. Concentrations are expressed in mg/L. Spot an error? Email support@argostellus.com.

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