Impact of Sustainable Groundwater Management Strategies on Nitrate Loading
Bhavna Arora is a Research Scientist in the Energy Geosciences Division at Lawrence Berkeley National Laboratory. She currently serves as the lead for a newly launched Carbon Removal and Mineralization Program. With a Ph.D. in Geoscience from Texas A&M University, her research has focused on advancing predictive understanding of biogeochemical processes in heterogeneous porous media, with the overarching goal of quantifying the impacts of climate and land use changes on ecosystem functioning.
Groundwater contamination from nitrate in agricultural regions is an environmental and human health concern worldwide. In agriculturally intensive regions, it is imperative to understand how shifts in management practices can enhance or mitigate nitrogen loading to groundwater. In California, agricultural managed aquifer recharge (AgMAR) is a strategy whereby surface water is used to intentionally flood croplands to recharge underlying aquifers. In this study, we use a process-rich numerical model to understand the effects of AgMAR management strategies (i.e., by varying the frequency, duration between flooding events, and amount of water) on nitrate leaching to groundwater under different soil textural configurations and antecedent soil conditions. Modeling results suggest that fine textured sediments can mitigate nitrogen loading to groundwater. In contrast, applying water all-at-once rather than in increments transports higher concentrations of nitrate deeper into the soil profile, which may exacerbate groundwater quality. We conclude that AgMAR options can be designed to reduce nitrate loading to groundwater, while specifically accounting for lithologic heterogeneity, antecedent soil moisture conditions, and depth to the water table.