Farmer driven water conservation policy on the Ogallala aquifer reduces the environmental footprints of crop production

Abstract

The Ogallala Aquifer underlies 45 million hectares, supporting the robust agricultural economy of the US Great Plains and providing water for about 1.9 million people. The aquifer's long-term viability is threatened though due to severe depletion. Pumping reductions of 25–30 % are required to stabilize water levels on a decadal scale. Legislation has been passed in Kansas to reduce groundwater extraction while supporting productivity and economic viability. One outcome is the Local Enhanced Management Area (LEMA) program, where farmers set water-conservation targets in a region. Our objective was to study the environmental benefits of implementing water-conserving cropping systems in the Sheridan-6 LEMA (longest running LEMA). The Integrated Farm System Model (IFSM), verified with region-specific data, was used to compare simulated cropping systems within the LEMA to those in the surrounding region using conventional crop irrigation management. We found that LEMA management, which includes reduced water use and altered cropping, has provided environmental benefits with a slight to moderate reduction in crop yields (1.2–15 %). Totaled over the LEMA, crop life cycle reductions were found for blue water use (28 %), reactive N losses (1.4 %), fossil energy use (22 %) and GHG emissions (20 %). Considering the environmental intensities expressed per unit of grain produced, LEMA policies decreased blue water (24 %), energy (18 %), and C (15 %) footprints. The exception was the N footprint which increased slightly due to reduced crop yields with similar N loss. The main driver of the reduced impact was decreased water use in crop irrigation, followed by changes in cropping strategies where more water-demanding crops (corn and soybean) were replaced by less water-demanding crops (sorghum and wheat). Replicating LEMA-type policies more widely across the region can be a viable solution (environmental and economic) to stabilize the Ogallala Aquifer water levels for the next few decades, as demonstrated by this and previous research.