In Hot Water? How Climate Change May (or may not) Affect the Groundwater Resources of Texas

The 2007 report by the Intergovernmental Panel on Climate Change suggests that Texas is likely to see a warmer climate, a decrease in mean annual runoff, an increase in flow seasonality, and an increase in the number of extreme drought events. All of these are likely to affect the water resources of Texas, including the groundwater resources. In our assessment of the susceptibility of Texas's aquifers to climate change, how quickly an aquifer recharges, the geologic setting, and land and water use will dictate how climate change may affect any given aquifer. Groundwater resources with high recharge rates, such as karstic aquifers like the Edwards (Balcones Fault Zone) Aquifer, and highly permeable clastic aquifers, like the Lipan Aquifer, are very susceptible to changes in climate while others with much slower recharge rates would not show effects for decades if not centuries. The groundwater resources in dipping clastic aquifers—aquifers with an unconfined recharge zone updip and a confined zone downdip such as the Trinity Aquifer north of the Colorado River, the Carrizo-Wilcox Aquifer, and the Gulf Coast Aquifer—are unlikely to be affected by climate change influenced recharge as long as the flux of water moving downdip remains less than the total recharge rate. General municipal and agricultural water use is expected to increase due to changes in climate; however, increases in water use due to expected increases in population in Texas are expected to be far greater. Nonetheless, climate change could induce greater reliance on groundwater if surface water resources become less reliable, and increases in agricultural usage would increase the depletion rate of the Ogallala Aquifer and lower water levels in other aquifers. More research is needed to better understand what the climate models suggest for Texas and recharge processes.