Water use conflict: a characterization and water quantity study in an agriculturally stressed subcatchment in Southwestern Ontario

Abstract

Observed data and climate change predictions indicate that water resources are vulnerable, especially in areas of water use conflict. This research uses various techniques to develop a conceptual water quantity study for 2016 for the Lower Whitemans Creek subcatchment (sandy and unconfined aquifer) in southwestern Ontario, Canada. This was done in order to improve the understanding of water dynamics and quantity in this region of water use conflict. Flow data and tracer (stable isotopes, electrical conductivity and Rn-222) suggested a higher groundwater discharge in the lower portion of the subcatchment than in other locations. An evaluation of long-term data (1960-2015) revealed that recharge is becoming increasingly unpredictable due to the effects of climate change. The results of the study analysis raise concerns about the quantity of water that is currently permitted for the irrigation of specialty crops. Specifically, given data acquired in 2016, water withdrawal permits allow for the taking of up to 51% of the potential recharge from the subcatchment. Compared to previous years, 2016 experienced lower precipitation (898 mm/yr), lower runoff (169 mm/yr), higher evapotranspiration (543 mm/yr) and lower potential recharge (355 mm/yr). The agricultural and anthropogenic water demands for 2016 showed that the subcatchment had a higher water requirement (1.69 mm/yr.km2) compared to the subwatershed (0.03 mm/yr.km2). Approaches used in this research can be used to assess the impact, challenges and opportunities of agricultural and water management in similar areas of water use conflict.