Investigation of Lake and Wetlands Influence on Streamflow in Mesoscale Precambrian Shield Watersheds Using IsoWATFLOOD, A Tracer-Aided Hydrologic Model

Hydrologists continue to be challenged in accurately predicting spatial variation in storage, runoff, and other hydrological processes in both natural and disturbed landscapes. Lakes and wetlands are important hydrologic stores in Precambrian shield watersheds. Identifying how they affect streamflow, independently and/or collectively is a challenge. Tracer-aided hydrologic modeling coupled with field-based stable isotope surveys offer a potentially powerful approach to investigation of mesoscale streamflow generation processes because the influence of evaporative enrichment generates a distinct signature of the surface water endmember, and continuous and distributed simulated streamflow can be tested against field observations under a range of flow conditions. The main objectives of this research are to investigate the influence of lakes and wetlands on streamflow generation by developing application of the tracer-aided hydrologic model isoWATFLOOD for the ~ 15275 km² Sturgeon - Lake Nipissing - French River (SNF) basin located on the Precambrian Shield in Northeastern Ontario, Canada. Monthly surveys of δ¹⁸O and δ²H in river flow were collected between 2013 to 2019 (weekly to monthly) across eight sub-catchments, with supporting observations of volumes and stable isotopes in snowcores, snowmelt, precipitation and groundwater. Application of the hydrologic model isoWATFLOOD to the SNF Basin is developed for the first time, allowing for simulation of discharge and stable isotopes in streamflow and soil moisture across multiple sub-catchments. In model building, consideration of differences in quaternary geology, landcover, and sub catchment locations are considered.  Landcover ranges from the boreal forests to impervious urban areas, while dominated by temperate forest, with some coverage of agriculture/disturbed impacted systems; several major sub-catchments having hydropower regulations. Previous statistical analysis has highlighted the importance of wetlands, lakes, and quaternary geology as influential on differences in hydrologic and isotope response in SNF watershed, as a result, model building is considering different landcover types as lakes and wetlands. Six different Landover are considered for generating Group Response Units (GRUs). The model is calibrated using discharge and stable water isotope.  IsoWATFLOOD can represent variation in streamflow generation across the study area. Identifying the different impacts of lakes and wetlands on streamflow generation processes in study area by applying isoWATFLOOD for the SNF watershed will be the main achievement of this study.