Evaluating the Effectiveness of Groundwater Conservation Districts in the Gulf Coast Aquifer of Texas

Due to the recent severe drought, groundwater management in Texas has never been more important. Texas is broken up into 96 autonomous Groundwater Conservation Districts (GCDs) charged with managing groundwater within their borders. This study, which won Texas A&M's 2012 Margaret Sheather Memorial Award in Statistics, examined the 26 GCDs covering the Gulf Coast aquifer to determine whether each GCD has had a positive effect on water levels in the aquifer. We also looked at the aquifer as a whole to determine whether GCDs are doing an efficient job of conserving water in the aquifer.

This analysis was complicated by the irregular nature and sparseness of water level measurements. To overcome this, a new technique was developed to remove the effect of seasonal fluctuations in water levels (via least squares) and combine a set of sparse, unevenly spaced, covariance nonstationary measurements from many wells into a single, evenly spaced, covariance stationary time series for each region. Intervention analysis using a Box-Tiao ARIMAX model was then conducted on each time series. This analysis enabled us to determine not only which districts were effectively conserving groundwater, but also how long it took conservation measures to impact groundwater levels.