HGSD data from 2019-23 shows the Greater Houston area continues to experience subsidence, or the collapsing of the land due to movement beneath the earth’s surface. HGSD General Manager Mike Turco said the phenomenon is often caused by groundwater withdrawal.
Per the HGSD, which regulates groundwater and monitors subsidence, northwest Harris County has seen increases in subsidence in the last four years.
“Those areas are primarily on groundwater, and ... we’ve seen rates pick up,” Turco said.
To alleviate subsidence, water authorities must follow HGSD’s regulatory plan and have 60% of their jurisdictions using surface water by the end of this year and 80% by 2035. This includes the North Harris County Regional Water Authority, which plans to expand its system to Tomball in the next five years.
What’s happening
The North Harris County Regional Water Authority is working on several projects to convert groundwater use to surface water use. Officials said about 32%-34% of the NHCRWA’s total water usage comes from surface water.
NHCRWA General Manager Jun Chang said most of the authority’s projects for the 2025 surface water deadline focus on expanding water lines. Loops of water lines connect municipal utility districts to pump stations, and each loop expansion helps create a more interconnected internal distribution system.
Most projects are paid for through bonds, funds from state entities and co-funding agreements. Board member Mark Ramsey said the NHCRWA is $2.7 billion in debt, and it’s expected to climb to $7 billion in the next 10 years. He said he hopes the Texas Legislature can provide “regulatory relief” to avoid unsustainable water rates.
The NHCRWA plans to connect its distribution system to Tomball by 2029. The $119.57 million project, currently in the planning stages, will supply surface water to multiple water plants in Tomball to support the city’s future growth.
Although the project helps the NHCRWA meet its 2025 surface water conversion deadline, Tomball City Manager David Esquivel said the city has no plans to rely solely on NHCRWA’s water, calling it unreliable and not guaranteed. Tomball operates its own water system, which relies on groundwater.
Chang said the NHCRWA has been talking with Tomball officials since 2018, reassuring them they would have a reliable surface water supply if they converted the city to surface water.
In April, the NHCRWA more than doubled the amount of surface water it could receive after completing the first phase of the Northeast Water Purification Plant expansion project. Chang said the water authority now receives 82 million gallons of surface water per day from Houston.
The background
Water rates customers pay correlate to how much debt is incurred from bonds issued for building water infrastructure, Chang said.
Despite ongoing projects, the NHCRWA’s rates are now at their lowest in a decade after the board cut rates over the past two years following the election of three new board members who unseated longtime incumbents in 2022.
While the cuts provide short-term relief for water users, Chang said a financial adviser estimated they could only last another six months before an increase is likely. The NHCRWA could see rates exceed $8 per 1,000 gallons by 2032.
HGSD General Manager Mike Turco described subsidence as the gradual sinking of land caused by the extraction of fluids from an aquifer system. As groundwater is pumped out, the water levels within the aquifer decline, causing the clay layers in the aquifer to depressurize and compact.
The impact
Population growth and water demand can impact subsidence, which can lead to more flooding, permanent land loss and infrastructure damage, Turco said. HGSD data shows that areas in Tomball saw an average of 0.32-1.19 centimeters of displacement per year between 2019-23.
Nestlewood Place and South Burberry Park Circle showed the highest subsidence rate during that period. Since measuring began there in 2011, it has experienced 13.7 total centimeters of displacement. At A.D. Dyess Park, the subsidence rate was only 0.32 centimeters per year, but the area saw 16.8 total centimeters of displacement since 2007.
The 77375 ZIP code in the east portion of Tomball contains locations with the second-highest and second-lowest annual subsidence rates compared to the rest of the city over the past four years. This area has also seen the largest population boom among subsidence hot spots in Tomball with 18,323 more residents between 2018-23, according to five-year estimates from the U.S. Census Bureau.
Subsidence measured at local monitoring stations include:
- Nestlewood Place and South Burberry Park Circle: 13.7 cm since 2011
- High Street and Village Square Drive: 6.6 cm since 2017
- Lee Road and Sweet Melody Lane: 21 cm since 2007
- Magnolia Boulevard and Friendship Drive: 10.5 cm since 2012
- Hwy. 249 and near Timbertech Lane: 24.80 cm since 2007
- South Pine Street and James Street: 37.6 cm since 2000
- A.D. Dyess Park: 16.8 cm since 2007
State Rep. Tom Oliverson, R-Cypress, filed House Bill 1643 on Dec. 17 to reduce the HGSD’s authority over the NHCRWA.
The bill aims to:
- Remove the NHCRWA from the HGSD’s jurisdiction
- Exempt the entity from groundwater reduction requirements
- Let the NHCRWA set their own timelines for transitioning to surface water use
“If we don’t get regulatory relief and we don’t get funding from other sources, that will drive [water rates] to $15, maybe $20 per 1,000 gallons, which is obviously an unsustainable number,” Ramsey said.
Reporter Nichaela Shaheen contributed to this report.
