Investigating hydrologic controls on 26 Precambrian shield catchments using landscape, isotope tracer and flow metrics

Abstract

AbstractAlthough many studies focus on catchment classification, hydrologists are challenged to find the most important variables for a meaningful catchment classification, especially in the heterogeneous environment of the Precambrian Shield. This study investigates landscape controls on hydrologic response by conducting a catchment classification of 26 catchments located within two Precambrian Shield watersheds (Sturgeon–French–Nipissing [SNF] and Muskoka) in central and Northeastern Ontario, Canada, using combinations of landscape characteristics (e.g. topography, geology, landcover), hydrometric variables, and stable isotopes of δ18O and δ2H in river flow. Weekly to monthly surveys of δ18O and δ2H in river flow were collected between 2013 and 2019. Flow metrics (e.g. Pardé coefficient and coefficient of variation of streamflow) were generated for 14 of the 26 rivers between 2008 and 2018. Principal component analyses (PCA) and Hierarchical Clustering on Principal Components (HCPC) analyses were used to identify variables controlling catchment clustering according to their similarities for four different scenarios. Despite their similar location along the southern edge of the Precambrian Shield, the 26 catchments generally clustered by watershed (SNF and Muskoka) with some exceptions. Differences in wetland and lake area (%), mean slope, and % area covered by glacialacustrine and glaciofluvial outwash deposits were the most influential variables in catchment classification. A positive correlation between % wetland area and streamflow stable isotope damping ratios suggests greater % wetland area (with shallow and potentially seasonally variable surface areas and/or hydrologic connection) observed in the SNF catchments increases variability in the influence of evaporative enrichment in SNF catchments. The catchment classification analyses in combination with stable isotopes of δ18O and δ2H were functional tools to investigate the combined influences of diverse types of catchment characteristics that lead to differences in hydrometric response. These results could support future studies focusing on generating hydrologic models and representing wetlands connectivity in the region.