Assessing the Prospects for Sustainability of Aquifers Supporting Irrigated Agriculture
Aquifers are under stress worldwide as a result of large imbalances between inflows and outflows. These imbalances are particularly severe in aquifers in semiarid regions that are heavily pumped for irrigation, such as the High Plains Aquifer (HPA) in the central United States.
If these aquifers are going to continue to support agricultural production, the current rate of water-level decline must be significantly reduced. In most cases, the only option will be to reduce pumping. The question is how much of a reduction is needed.
At the Kansas Geological Survey, we have developed a water-balance approach for rapid assessment of the impact of proposed pumping reductions and of the prospects for aquifer sustainability. This approach, which is particularly well suited for assessing the short- to medium-term (years to a few decades) response to management actions in seasonably pumped aquifers, also enables the net inflow (capture) term of the aquifer water balance and the specific yield to be directly calculated from water-level and water-use data.
Application to the data-rich Kansas portion of the HPA reveals that practically achievable reductions in annual pumping (approximately 20 percent to 25 percent) would have a large impact across the aquifer and could stabilize water levels in some areas for at least the near future.
Water resources managers are often in a quandary about the most effective use of scarce funds for data collection in support of aquifer assessment and management activities. In addition to water-level data, a greater emphasis should be placed on collection of reliable water-use data; greater resources devoted to direct measurement of pumping will yield deeper insights into an aquifer’s future.
Univiversity of Kansas, Lawrence, KS
