Groundwater Withdrawals Associated with Oil and Gas Production from Water Supply Aquifers in Texas: Implications for Water Management Practices

The demand for water in Texas is continuing to increase as population and industry grow. The Natural Resources Defense Council has indicated that Texas is at “extreme risk” and will require implementation of sustainable water management practices, particularly since groundwater supplies much of the state’s freshwater demands. This study evaluated the occurrence and extent of produced water discharge with low total dissolved solids associated with oil and gas production from the Carrizo-Wilcox formation in Texas. We conducted analyses of produced water discharge permits from the Railroad Commission of Texas, which included limited water quality data of permitted discharges, the groundwater quality in the Carrizo-Wilcox formation from which the producing wells extract, and the potential conflicts between state permitted discharge quantities and ongoing aquifer conservation programs in the area. Our findings show that the Railroad Commission of Texas, the governing agency for Texas oil and gas development, permits produced water to be discharged into surface waters if the discharged water quality meets Texas Surface Water Quality Standards set by the Texas Commission on Environmental Quality for the specific receiving water body. Nearly 5,331,975 cubic meters (4,323 acre-feet) of groundwater each year is discharged as produced water from the Carrizo-Wilcox Aquifer to surface waters through discharge permits designated as “agricultural”. Based on an evaluation of the reported Whole Effluent Toxicity test data, 69 discharges of water from the Carrizo-Wilcox formation amount to total dissolved solids levels of less than 1,000 milligrams per liter, 35 of the discharges have total dissolved solids levels of 1,000–1,500 milligrams per liter, and 20 of the discharges have total dissolved solids levels of 1,500–4,000 milligrams per liter. Forty four percent of the referenced discharges exceed the Texas Commission on Environmental Quality’s secondary drinking water standard for total dissolved solids (1,000 milligrams per liter), and there is potential that water quality changes are under-reported, as permit values are stagnant but produced water quality generally degrades over time. However, the water quality of the discharges complies with general requirements for several water uses associated with agricultural and industrial practices, although it is understood water quality would need further characterization prior to use. Evidence found in this study suggests that the lack of communication regarding the identified discharges and the associated water quality could lead to conflicting groundwater practices that, at least on a local level, could have negative impacts, such as contributing to aquifer overexploitation. This overextraction in turn is expected to negatively impact existing groundwater conservation efforts and the future of water supply of Texas. © 2021 Katie Coeckelenbergh, Dorina Murgulet, Kristine Uhlman, Chris Vickers.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu