A Regional Analysis of Groundwater Depletion for the Ogallala Aquifer in Texas

Groundwater drawn from the Ogallala Aquifer is widely used to support irrigated agriculture on the Texas High Plains. While it is commonly accepted that the aquifer is being drawn down at an average rate of about 30 cm (1 ft) per year in West Texas, this rate masks considerable variability in the region. To better understand the spatial variability in groundwater depletion, tabular data from the Texas Water Development Board state well-monitoring network were geocoded and used to map the saturated thickness of the aquifer for each year from 1990 to 2004. The saturated thickness for 1990 was then subtracted from the saturated thickness in 2004 to map the change in the saturated thickness of the aquifer over the 15 year period.

The results from this study clearly show a strong spatial correlation between intensive irrigated agriculture and both the thickness of the aquifer and rates of aquifer depletion. When a map of center pivot irrigation systems is overlaid on the maps of saturated thickness and saturated thickness change, it becomes obvious that the most intensive irrigated agriculture has developed where the aquifer is thickest and these areas closely correspond to the highest rates of aquifer depletion. Conversely, the areas with few center pivot systems correspond to areas where the aquifer is relatively thin and the rates of depletion are very low. In a few of these areas there is also some evidence to suggest a small rise in water surface elevation.