Towards hydrological model calibration and validation: simulation of stable water isotopes using the isoWATFLOOD model

Abstract

Calibration and validation of hydrological models is a challenge, particularly in remote regions that are minimally gauged. This paper develops a novel methodology for large-scale (>1000 km 2 ) hydrological model calibration and validation using stable water isotopes founded on the rigorous constraints imposed by the need to conserve both water mass and stable isotopes simultaneously. The isoWATFLOOD model is applied to five basins within the Fort Simpson, Northwest Territories region of northern Canada to simulate stream discharge and oxygen-18 signals over a 3-year period. The isotopic variation of river discharge, runoff components, and evaporative fractionation are successfully simulated on both a seasonal and continual basis over the watershed domain to demonstrate the application of isotope tracers to regional hydrologic calibration. The intended application of this research is to remote, large-scale basins, showing promise for improving predictions in minimally gauged basins and climate change research where traditional, rigorous approaches to constraining parameter uncertainty may be impractical. This coupled isotope-hydrological (i.e. iso-hydrological) approach to modelling reduces the number of possible parameterizations, resulting in potentially more physically-based hydrological predictions. isoWATFLOOD provides a tool for water resource managers and utilities to use operationally for water use, allocation, and runoff generation estimations. Copyright

Using isotopes to constrain water flux and age estimates in snow-influenced catchments using the STARR (Spatially distributed Tracer-Aided Rainfall–Runoff) model

“…The model's injection of an overestimated flux of depleted snowmelt water into the catchment likely has a carry-over effect underestimating streamflow isotopes through the year 2007 and early 2008. This exceptional event illustrates how intimately snow processes are linked not only to simulating water but also, crucially, to isotope fluxes in northern catchments (Stadnyk et al, 2013;Smith et al, 2016).…”

“…Historically, tracer-aided model applications have typically been lumped/semi-lumped conceptual models (Neal et al, 1988;Barnes and Bonell, 1996;Hrachowitz et al, 2013;Smith et al, 2016), though some modelling studies incorporate spatial variability in the model parameterization (Stadnyk et al, 2013;. Spatially and temporally limited tracer data are typically a considerable constraint in tracer-aided modelling (Delavau et al, 2017), in particular if interest lies in understanding spatially distributed flow processes over longer than event timescales.…”

Identification of geographical influences and flow regime characteristics using regional water isotope surveys in the lower Nelson River, Canada

“…These sites are ideal candidates for isotope-mass balance modelling as end members are isotopically distinct, different basins exhibit different characteristic responses and the basins are gauged but unregulated. The capability to continuously simulate both streamflow and isotopic composition using the isoWATFLOOD model (Stadnyk et al 2013) in the LNRB will additionally facilitate continuous records of isotopic variability in response to hydrologic change, enabling a more thorough understanding of hydrologicisotopic response and reasons for hydrologic change at various scales.…”

Using stable isotopes to estimate travel times in a data‐sparse Arctic catchment: Challenges and possible solutions

“…Tracers provide integrated insight into the hydrological functioning of catchments and have been used previously to assess water sources and flow paths in Arctic and permafrost settings (Ala‐aho, Soulsby, et al, ; Blaen, Hannah, Brown, & Milner, ; Lamhonwah, Lafrenière, Lamoureux, & Wolfe, ; Obradovic & Sklash, ; Song et al, ; Yi et al, ). In addition to their capacity to quantify water provenance, flow paths, and transit times, tracer studies provide insights for calibration and testing more detailed conceptual and numerical models at different spatial scales (Ala‐aho, Tetzlaff, McNamara, Laudon, & Soulsby, ; Birkel, Soulsby, & Tetzlaff, ; Soulsby et al, ; Stadnyk, Delavau, Kouwen, & Edwards, ; van Huijgevoort, Tetzlaff, Sutanudjaja, & Soulsby, ).…”