July 31, 2014


Subsidence is a public safety concern in Houston and Surrounding areas

Friendswood, TX, July 31, 2014 – The Texas Water Development Board (TWDB) has released calculations of the total estimated recoverable storage (TERS) for aquifers across the State, including aquifers in Harris and Galveston Counties within the Harris-Galveston Subsidence District (HGSD). The TERS is an estimate of the total amount of groundwater recoverable from the aquifers of the state without regard for quality of the water withdrawn or any adverse impacts of the withdrawal, such as subsidence. Subsidence, resulting from groundwater withdrawal, is a major concern in Houston and surrounding cities in Fort Bend, Galveston, Brazoria, and Montgomery Counties.

“The total estimated recoverable storage is defined as the estimated amount of groundwater within an aquifer that accounts for recovery scenarios that range between 25 percent and 75 percent of the porosity-adjusted aquifer volume. In other words, we assume that only 25 to 75 percent of groundwater held within an aquifer can be removed by pumping. Total estimated recoverable storage values may include a mixture of water quality types, including fresh, brackish, and saline groundwater, because the available data and the existing groundwater availability models do not permit the differentiation between different water quality types. The total estimated recoverable storage values do not take into account the effects of land surface subsidence, degradation of water quality, or any changes to surface water-groundwater interaction that may occur as the result of extracting groundwater from the aquifer.” – (TWDB REPORT. GAM TASK 13-037: TOTAL ESTIMATED RECOVERABLE STORAGE FOR AQUIFERS IN GROUNDWATER MANAGEMENT AREA 14, Released June 9, 2014)

The TERS data calculated by the TWDB has limited applicability in Houston and the surrounding areas. The Subsidence District will not utilize the TERS data in its regulatory plan due to its lack of consideration for the impacts of groundwater withdrawal on subsidence. “Calculating the total amount of recoverable water from an aquifer without consideration for the impacts (i.e. water-level decline, degrading water-quality, subsidence, etc.) caused by withdrawing that amount of water is of little use to realistic water planning,” said Michael Turco, General Manager of the Subsidence District.

Serving the Gulf Coast community since 1975, the Harris-Galveston Subsidence District is the premier water management and subsidence authority in the Upper Gulf Coast Region in Texas. The District protects lives and property within the District from the impacts of land surface subsidence by providing reasonable regulation of groundwater withdrawal. The District works with local stakeholders and regional planners to insure the long-term viability of all water resources while minimizing the threat of subsidence.

If you would like more information about this topic, please contact Michael Turco at 281-486-1105 or email at mturco @


Wade, S., D. Thorkildsen, R. Anaya, 2014. GAM Task 13-037: Total Estimated Recoverable Storage for Aquifers in Groundwater Management Area 14.