ENVIRONMENT New report provides more data in ongoing subsidence debate
BY VANESSA HOLT & EMILY LINCKE
analyzing what the report means for their understanding of how subsid- ence is a ecting the area. Jim Spigener, president of the Lone Star Groundwater Conservation District board of directors, said at a Feb. 14 board meeting the agency would try to provide comments within the public comment period before the April 17 deadline. “The [ground] compaction data incorporated into the GULF-2023 model is not from Montgomery County or the Jasper Aquifer,” Spigener said in an email, citing the district’s technical consultants. “This ... further supports the need to perform Phase 3 of the [LSGCD] subsidence study.” O cials with the LSGCD previously told Community Impact they do not believe that subsidence can be attributed entirely to groundwater withdrawal based on current studies, and they questioned methodologies used. The LSGCD is in the process of conducting its own study, but o cials said that is on pause while it com- ments on the GULF-2023 study. O cials with the San Jacinto River Authority, which manages and provides surface water for the region, said the new study provides more accurate information on subsidence, which they believe is the result of groundwater withdrawal. SJRA General Manager Jace Hous- ton said the new model uses informa- tion from a broad range of sources. “This latest version will increase the accuracy even more, especially around the edges of the model where data is more recent,” Houston said. WA
LOSING GROUND Subsidence contours in the GULF-2023 report outline the areas in the Greater Houston region that have been sinking at approximately the same rate since measurements were rst taken in 1906.
On the heels of an August 2022 report from the University of Houston on land subsidence, a Jan. 12 report from the Oklahoma-Texas Water Science Center further outlines land sinking that has occurred in the Greater Houston area, according to information released by the Texas Water Development Board. As of 2021, The Woodlands saw an average of 2.5 feet of sinking over the past century, and Conroe saw an average of 1.5 feet, according to the Jan. 12 report, with most of the land movement occurring since 1987. This gradual, vertical decline is known as subsidence, or the sinking of the land due to movement beneath the earth’s surface. John Ellis—who authored the Jan. 12 study also known as the GULF-2023 report and who serves as the center’s Gulf Coast Studies chief— said this subsidence worsens ooding in watersheds by “altering the base ood elevations.” “[Subsidence] ... can result in permanent loss of land, increased risk of ooding and the damage to the infrastructure,” Ellis said. Subsidence is chie y caused by pumping water from underground reserves, which compacts sublayers of clay and silt in aquifers beneath the Earth’s surface, according to a Uni- versity of Houston geological study released in August. The resulting sinking is a problem experienced all over the Greater Houston area. O cials with local entities that govern water in The Woodlands area said in February they are still
Cumulative subsidence contours, 1906-2021
Key:
1-2 feet
2-3 feet 3+ feet
MONTGOMERY COUNTY
1
105
45
249
69
2
99
290
The area inside the 1-foot contour but outside of the 2-foot contour experienced 1-2 feet of subsidence between 1906 and 2021.
Montgomery
Liberty
Harris
Waller
Chambers
Average sinkage 1906-2021
Fort Bend
2 The Woodlands: 2.5 feet 1 Conroe: 1.5 feet
Galveston
Brazoria
N
SOURCE: OKLAHOMA TEXAS WATER SCIENCE CENTER COMMUNITY IMPACT
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