Cypress Edition | April 2023

Turco said a study on the impact of subsidence in the Cypress Creek watershed has not yet been done. Experts warned excessive groundwater pumping will make ood mitigation more dicult in Greater Houston communities where it is already challenging. “These [ooding events] are in the same areas where we are seeing subsidence rates at 1 1/2 to 3 centimeters per year,” Turco said. In addition to worsening ooding, subsidence also contributes to changes in drainage patterns, fault movement, and damages to wells and pipelines, according to the HGSD. Alternative sources Although the conditions that cause subsidence can be lessened if residents cut groundwater usage and switch to alternative water sources, the eects of subsidence are permanent, said

Robert Mace, water policy director at Texas State University. “If you reduce your pumping, you can then decrease the maximum subsidence that would have occurred,” he said. “But for the most part, land subsidence is a one-way trip. Once it’s compressed, it’s not coming back up.” To prevent subsidence from worsening, HGSD set pumping requirements for all water suppliers in Harris and Galveston counties in 2013. This includes the NHCRWA and the West Harris County Regional Water Authority, which both serve Cy-Fair. “We expect those subsidence rates to come down to near zero as we implement this plan,” Turco said. Danica Lloyd contributed to this report.

For more information, visit communityimpact.com .

While historical subsidence in downtown Houston along the Houston Ship Channel has stabilized, more recent subsidence has taken place in the fast- growing northern, northwestern and western portions of Harris County. HISTORICAL OUTLOOK

Cumulative feet of subsidence

12 345678910

CUMULATIVE SUBSISDENCE CONTOURS 19062021

Research shows certain parts of the Greater Houston region have seen higher levels of subsidence over time.

MONTGOMERY

LIBERTY

290

HARRIS

WALLER

CHAMBERS

GALVESTON

FORT BEND

BRAZORIA

GULF OF MEXICO

SOURCE: OKLAHOMATEXAS WATER SCIENCE CENTERCOMMUNITY IMPACT

CYPRESS EDITION • APRIL 2023