The Sheridan-6 Local Enhanced Management Area: An Ongoing Experiment in Groundwater Conservation

Abstract:

Many of the world's aquifers are under severe stress as a result of heavy pumping in support of irrigated agriculture. The High Plains aquifer in the state of Kansas is no exception. Intensive pumping in western Kansas has produced large water-level declines that threaten the continued viability of irrigated agriculture, the major economic driver for the region. In response to this condition, new management options focused on groundwater conservation have been developed. The most promising of these, the Local Enhanced Management Area (LEMA) program, is a grassroots-driven initiative supported by regulatory oversight. The first LEMA was established in 2013 in the 256-km² Sheridan-6 area in northwestern Kansas; the goal was to reduce average water use by 20%. We have assessed the first seven years of the LEMA operation (2013-2019) using water-level, water-use, and precipitation data. Controlling for climatic conditions, we find that water use has decreased 30% with respect to the 2005-2012 pre-LEMA period and the water-level decline rate has decreased 68%. The net inflow (all inflows to the aquifer minus all outflows except pumping) will eventually decrease in response to the pumping reductions, but that has yet to occur. As calculated with the method of Butler et al. (GRL – 2016), net inflow appears unchanged from that during the pre-LEMA period. Although the pumping reductions have been achieved with little economic impact, the pumping rate is still above the net inflow. As a result, water-level declines continue. We have developed a water balance approach to chart possible future conditions for the area. We find that as long as the pumping rate remains above the net inflow at the time of the reduction, the extension of the aquifer lifespan produced by the reduction will be limited (< a factor of two to three). The pumping rate must be reduced below the net inflow to more significantly extend the aquifer lifespan. The major uncertainties in the analysis are the rate of decrease in the net inflow and the lower limit to which it can fall. Monitoring conditions in Sheridan-6 and other current/proposed LEMAs will allow such uncertainties to be reduced and provide invaluable insights on how the aquifer responds to conservation-driven pumping reductions. Such insights will be applicable far beyond the High Plains aquifer in Kansas.