Spatiotemporal variability of water quality and stable water isotopes in intensively managed prairie watersheds

Abstract

AbstractLow‐relief and highly engineered prairie landscapes present many challenges for water quality modelling. Limited investigation has been carried out to determine whether drains, canals and diversions (artificial waterways) impact water quality relative to natural or naturalized systems or to assess the value of stable water isotopes as predictor variables for specific water quality metrics. The goal of this paper is to investigate the spatiotemporal variability of water chemistry in a typical prairie watershed by (1) comparing water quality and stable water isotopic ratios between naturalized and artificial waterways; (2) evaluating the relationships between topographic and land use characteristics, water quality and stable water isotopic ratios; and (3) expressing and predicting PO4 concentrations as a function of stable water isotopic ratios. Focus was on the 2509 km2 mostly agricultural Seine River Watershed located in southern Manitoba, Canada. Twenty‐four sampling sites located along naturalized river reaches, drains and diversions were visited once a week from May to June 2013. Surface water samples were collected and tested for physical water quality parameters and PO4 concentrations, δ2H and δ18O. Kruskal–Wallis tests show no significant differences in water chemistry among waterway types, while strong correlations were found between physical water quality parameters, PO4 concentrations, isotopic ratios and watershed characteristics. PO4 concentrations were successfully predicted from isotopic ratios using linear regression models. These results bear significant importance for the mostly ungauged prairie watersheds, thanks to the relative ease and lower cost of measuring stable water isotopic ratios in comparison to nutrient concentrations. Copyright © 2015 John Wiley & Sons, Ltd.