Vertical Land Motion of the High Plains Aquifer Region of the United States: Effect of Aquifer Confinement Style, Climate Variability, and Anthropogenic Activity
Justine Overacker, W. C. Hammond, Geoffrey Blewitt, Corné Kreemer
Abstract
Abstract We use GPS data to image vertical crustal velocities in the vicinity of the Great Plains physiographic province of the United States. In the southern Great Plains, we find crustal uplift of up to 2 mm/year in an area approximately 670 km × 280 km. This signal is spatially correlated with the area of greatest groundwater decline in the southern High Plains aquifer. To determine the uplift mechanism and its possible relation to aquifer depletion, we investigate changes in aquifer water content. Gravity data coupled with an elastic model show the uplift rate is consistent with hydrological unloading from anthropogenic aquifer depletion exacerbated by severe drought. Our model that encompasses two regions of greatest groundwater decline indicates a water volume loss of −5.1 km 3 /year is sufficient to match the observed signal. In other large aquifers, vertical crustal motions associated with groundwater depletion are often dominated by near‐field subsidence. Our results challenge the perception that vertical motions driven by aquifer depletion necessarily equate to near‐field subsidence. In the High Plains system, depletion causes near‐field uplift because of the combination of mass removal and the style of geologic reservoir. As current climate change models predict aggravated drought conditions in the southern Great Plains in the coming decades, we expect to see an increasing rate of uplift caused by groundwater depletion unless there is offsetting recharge or changes in water resource management.