Evaluation of Large-Scale Pumping and Hydraulic Fracturing on the Groundwater Resources in DeWitt County, Texas

The talk will present the results of a study performed by the Pecan Valley Groundwater Conservation District to investigate the potential impact that the production of  groundwater in the Gulf Coast Aqufier for hydraulic fracturing in Dewitt County would have on groundwater resources.  The investigation considered  large-scale impacts over  a 50-year planning period  and a spatial scale of hundreds of square miles and local impacts over several  months and a spatial scale of 3 to 10 square miles.  The large-scale impacts were simulated using the groundwater availability model  for the Gulf Coast Aquifer System adopted by the district and its neighboring districts for regional planning.  These simulations include estimated future pumping that was adjusted for the projected number of fracking events per year from 2010 to 2035 and possible drought events.  The small-scale impacts were simulated using an analytical code that accounts for multiple aquifer layers and is capable of accurate predictions for short well distances.  As part of the evaluation of the predicted drawdown impacts, the study investigated sources of uncertainty in model predictions and performed sensitivity and related analysis to quantify and bound the uncertainties.   The related analyses included a recalibration of the regional model to measured water levels and estimated aquifer properties in DeWitt County.  The results of the study are being used by the District to help develop management  strategies and groundwater rules to accomplish their mission.