Examining the impacts of precipitation isotope input (δ18Oppt) on distributed, tracer-aided hydrological modelling
Tracer-aided hydrological models are becoming increasingly popular tools as they assist with process understanding and source separation, which facilitates model calibration and diagnosis of model uncertainty (Tetzlaff et al., 2015; Klaus and McDonnell, 2013). Data availability in high-latitude regi...
| Published in: | Hydrology and Earth System Sciences |
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| Main Authors: | , , |
| Format: | Text |
| Language: | English |
| Published: |
2018
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| Subjects: | |
| Online Access: | https://doi.org/10.5194/hess-21-2595-2017 https://www.hydrol-earth-syst-sci.net/21/2595/2017/ |
| Summary: | Tracer-aided hydrological models are becoming increasingly popular tools as they assist with process understanding and source separation, which facilitates model calibration and diagnosis of model uncertainty (Tetzlaff et al., 2015; Klaus and McDonnell, 2013). Data availability in high-latitude regions, however, proves to be a major challenge associated with this type of application (Tetzlaff et al., 2015). Models require a time series of isotopes in precipitation ( δ 18 O ppt ) to drive simulations, and throughout much of the world – particularly in sparsely populated high-latitude regions – these data are not widely available. Here we investigate the impact that choice of precipitation isotope product ( δ 18 O ppt ) has on simulations of streamflow, δ 18 O in streamflow ( δ 18 O SF ), resulting hydrograph separations, and model parameters. In a high-latitude, data-sparse, seasonal basin (Fort Simpson, NWT, Canada), we assess three precipitation isotope products of different spatial and temporal resolutions (i.e. semi-annual static, seasonal KPN43, and daily bias-corrected REMOiso), and apply them to force the isoWATFLOOD tracer-aided hydrologic model. Total simulated streamflow is not significantly impacted by choice of δ 18 O ppt product; however, simulated isotopes in streamflow ( δ 18 O SF ) and the internal apportionment of water (driven by model parameterization) are impacted. The highest-resolution product (REMOiso) was distinct from the two lower-resolution products (KPN43 and static), but could not be verified as correct due to a lack of daily δ 18 O ppt observations. The resolution of δ 18 O ppt impacts model parameterization and seasonal hydrograph separations, producing notable differences among simulations following large snowmelt and rainfall events when event compositions differ significantly from δ 18 O SF . Capturing and preserving the spatial variability in δ 18 O ppt using distributed tracer-aided models is important because this variability impacts model parameterization. We achieve an understanding of tracer-aided modelling and its application in high-latitude regions with limited δ 18 O ppt observations, and the value such models have in defining modelling uncertainty. In this study, application of a tracer-aided model is able to identify simulations with improved internal process representation, reinforcing the fact that tracer-aided modelling approaches assist with resolving hydrograph component contributions and work towards diagnosing equifinality. |
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