A Pivotal New Approach to Groundwater Quality Assessment

Areas of intensive agriculture and irrigation are prone to groundwater nitrate contamination, which can threaten drinking water supplies. Irrigation center pivots are a common feature in heavily irrigated regions and have the potential to provide insight into subsurface redox chemistry. In this study, we hypothesized that the same geochemical condition(s) that causes rust staining on center pivot systems will strongly influence groundwater nitrate concentrations. In south central Nebraska, 700 center pivot irrigation systems were classified by appearance of iron staining (full rust, part rust, or no rust) using Google Earth imagery and/or ground-based surveys. Ground-based observation of 270 center pivots yielded the same classifications as Google Earth imagery 83% of the time. Groundwater nitrate concentrations correlated with pivot classifications show lower nitrate concentrations in full rust and part rust pivots when compared with no rust pivots. The novelty of this work is to provide a framework for understanding groundwater quality using an inexpensive method applicable to both established and developing agricultural communities.