Agricultural nutrient transport to groundwater under changing climate and land use

Jana Levison, Elisha Persaud, Shoaib Saleem

Dans les comptes rendus d’articles de la conférence: GeoNiagara 2021: 74th Canadian Geotechnical Conference; 14th joint with IAH-CNC

ABSTRACT: application on agricultural fields. Changing land uses and climate change will concurrently influence nutrient concentrations in receiving waters. Two contrasting, yet complimentary methodologies for investigating future groundwater contamination under conditions of changing land use and climate in agricultural watersheds are presented. First, an index-based method that modifies the conventional DRASTIC-LU approach has been developed to better understand how groundwater contamination risk may change by mid-century, under dynamic climate and land use forcing. This is a valuable screening tool to understand future groundwater contamination risk and to guide monitoring programs in rural watersheds. A case study is presented for the Upper Parkhill watershed in southwestern Ontario (Lake Huron basin). The manner in which agricultural land use is represented (e.g. inclusion of crop rotation and tile drainage data) influences model performance and predicted changes in groundwater contamination risk. Second, a fully integrated hydrologic model (HydroGeoSphere) was coupled with the root zone water quality model (RZWQM2) to develop water flow and nitrate transport models in the Lynn River watershed (Lake Erie basin) under future land use and changing crop scenarios. Nine predictive scenarios were examined, using three crop rotations (corn-soybean, continuous corn, corn-soybean-winter wheat-red clover) and data from three climate models. In the simulated future period, it is predicted that less water will be available and groundwater nitrate will be lower. The best management practices (BMP) scenario (corn-soybean-winter wheat-red clover rotation) produces significantly lower groundwater nitrate concentrations than the other rotations. Thus, adoption of BMPs can reduce potential negative impacts of future climate change on groundwater quality, especially in vulnerable settings. In order to better manage and protect groundwater supplies, various approaches should be employed to predict future contamination potential or risk.

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