Using isotopic tracers to enhance routine watershed monitoring - Insights from an intensively managed agricultural catchment

Elisha Persaud; Jana Levison; Genevieve Ali; Clare Robinson

doi:10.1016/j.jenvman.2023.118364

Using isotopic tracers to enhance routine watershed monitoring - Insights from an intensively managed agricultural catchment

J Environ Manage. 2023 Oct 15:344:118364. doi: 10.1016/j.jenvman.2023.118364. Epub 2023 Jul 1.

Authors

Elisha Persaud¹, Jana Levison², Genevieve Ali³, Clare Robinson⁴

Affiliations

¹ School of Engineering, University of Guelph, 50 Stone Road East, Guelph, Ontario, N1G 2W1, Canada; Morwick G360 Groundwater Research Institute, University of Guelph, 50 Stone Road East, Guelph, Ontario, N1G 2W1, Canada. Electronic address: epersaud@uoguelph.ca.
² School of Engineering, University of Guelph, 50 Stone Road East, Guelph, Ontario, N1G 2W1, Canada; Morwick G360 Groundwater Research Institute, University of Guelph, 50 Stone Road East, Guelph, Ontario, N1G 2W1, Canada.
³ Department of Earth and Planetary Sciences, McGill University, 3450 University Street, Montreal, Quebec, H3A 0E8, Canada; Department of Geography, McGill University, 805 Sherbrooke Street West, Montreal, Quebec, H3A 0B9, Canada; School of Environmental Sciences, University of Guelph, 50 Stone Road East, Guelph, Ontario, N1G 2W1, Canada.
⁴ Department of Civil and Environmental Engineering, Western University, 1500 Richmond St, London, Ontario, N6A 5B9, Canada.

PMID: 37399619
DOI: 10.1016/j.jenvman.2023.118364

Abstract

Experimental (research-based) and non-research-based watershed monitoring programs often differ with respect to sampling frequency, monitored variables, and monitoring objectives. Isotopic variables, which are more commonly incorporated in research-based programs, can provide an indication of water sources and the transit time of water in a catchment. These variables may be a valuable complement to traditional water quality monitoring variables and have the potential to support improved hydrologic process-related insights from long term monitoring programs that typically have low resolution sampling. The purpose of this investigation is to explore the utility of incorporating isotopic variables (specifically δ¹⁸O, δ²H, and ²²²Rn) into routine monthly sampling regimes by comparing insights gained from these variables to monitoring only specific conductivity and chloride. A complete annual cycle of monthly groundwater and surface water monitoring data collected from the Upper Parkhill watershed in southwestern Ontario, Canada was used to characterize baseline watershed conditions, evaluate watershed resilience to climate change, and examine contamination vulnerability. Study results provide an improved understanding of appropriate tracer use in agricultural regions with isotopic variables able to provide important insights into the seasonality of hydrologic phenomena, such as the timing of groundwater recharge. A comparison of monitoring variables to present-day hydro-meteorological conditions suggests the importance of a winter dominated hydrologic regime and the potential influence of changes in precipitation on groundwater-surface water interactions. Estimated transit time dynamics indicate the likelihood for rapid contaminant transport through surface and shallow subsurface flow and highlight the possible effects of agricultural tile drainage. The sampling approach and data analysis methods adopted in this study provide the basis for improving routine watershed monitoring programs in agricultural regions.

Keywords: (222)Rn; Agricultural watershed; Mean transit time; Stable water isotopes; Watershed monitoring.

MeSH terms

Agriculture
Environmental Monitoring / methods
Groundwater*
Ontario
Water Pollutants, Chemical* / analysis
Water Quality

Substances

Water Pollutants, Chemical