New research looks at groundwater use
A new report from the U.S. Geological Survey broadens groundwater research in Montgomery and Harris counties, using an updated scientific tool that provides subsidence estimates from more than a century ago.
The report, released in early January, offers no significant changes in current subsidence amounts, but provides historical estimates for groundwater districts to use as they deal with an increase water demands due to population growth.
The USGS report about the tool, published Jan. 12, examines more recent subsidence in Montgomery County as well as northern and western Harris County.
Traditionally, these regions were not a focus in early studies, said John Ellis, USGS Gulf Coast Studies Section Chief and lead author of the report.
“Those (earlier studies) were focused mainly in the areas with historical groundwater use, like Central Harris County, Pasadena, Baytown (and) Texas City,” said Ellis, who has worked with the federal agency for nine years, with a background in numerical modeling. “This report really shows the movement of subsidence in (the) northward, northwestward and westward (greater Houston area).”
Subsidence is the sinking of the ground because of underground material movement, according to the National Oceanic and Atmospheric Administration. It’s most often caused by the removal of water, oil, natural gas or mineral resources from the ground by pumping, fracking or mining activities. It has been a growing concern for decades in the area because it can increase the risk of flooding and contribute to infrastructure damage.
In 1983, an entire subdivision sank into Galveston Bay due to subsidence. A picture of Ellis outside of the former Brownwood subdivision can be found on the agency’s website, where he holds a leveling rod that shows between 1915-2021 a loss in land surface the height of a 9foot-tall Christmas tree.
“(The report) shows through many figures ... that there’s a well established connection between long current subsidence rates and groundwater level declines in the greater Houston area,” he said.
Among the focal areas of the report is the Jasper Aquifer, which provides water mainly to Montgomery County, and subsidence caused by compaction.
Compaction is the process of fine-grained sediments like clays and silts, within an aquifer system, rearranging into stacks — imagine plates stacked in the cupboard — due to groundwater level declines, according to the USGS website.
While compaction is the process, subsidence is the result, Ellis said.
Subsidence caused by compaction in the Jasper Aquifer accounted for 16 percent in the Spring area, 33 percent in The Woodlands and 57 percent in Conroe, according to the report.
As of 2021, Spring lost more than 4 feet of land due to subsidence. The Woodlands lost more than 2 feet of land, while Conroe lost more than 1 foot.
“Based on many years of available data, as long as groundwater levels continue to decline or remain near historical minimums for a long time, subsidence will continue to happen,” Ellis said. “Just at a reduced rate.”
The predictive tool will be used to run a number of future scenarios to determine future subsidence rates, as a means to help subsidence districts and groundwater districts with planning and decision making. The federal agency collaborated with the Harris-Galveston and Fort Bend subsidence districts, as well as the Texas Water Development Board to create the tool to help with their regulatory plans.
Officials with the Lone Star Groundwater Conservation District, which represents Montgomery County, said they have a different mission than the subsidence districts, citing their responsibility to protecting people’s property rights, which they said the predictive tool does not account for.
“It’s not that it’s bad … it was not designed initially for joint planning for (groundwater conservation districts), which have a different statutory mandate than the subsidence districts do,” said Stacey Reese, legal representative at Lone Star.
The agency wants to weigh in on the tool before the state water board requires its use.
The water development board oversees groundwater conservation districts and approve regulatory plans, said Jim Spigener, general manager at Lone Star.
“If we’re going to make decisions that are going to affect the citizens of Montgomery County … we certainly want to make sure we have as good of a picture as we have to regulate from this,” Spigener said.
The water development board will have a 90-day period where districts and the public can comment on the predictive tool, which began on Jan. 17.