Evaluation and uncertainty assessment of weather data and model calibration on daily streamflow simulation in a large-scale regulated and snow-dominated river basin

Abstract

The choice of proper input data and suitable calibration schemes is challenging in the hydrological modeling of higher-latitude watersheds with their unique hydro-climatic conditions. Based on the Soil and Water Assessment Tool (SWAT) and Sequential Uncertainty Fitting Program (SUFI2) of the SWATCUP tool, our study revisits various climate data and calibration schemes, and develops a more automatic calibration framework to thoroughly assess model performance in simulating Snow Water Equivalent (SWE) and resulting streamflow in a cold region watershed, the Peace River Basin (PRB) in western Canada. We evaluated the effects of (1) the observed and two widely used gridded climate data sources; (2) unrealistic snow parameter combinations arising from SUFI2-SWATCUP parameter sampling; and (3) ‘calibration schemes’ including the choice of (i) objective function, (ii) number of simulations in each calibration iterations, (iii) regional versus global parameterization and calibration schemes, and (iv) single-variable (streamflow) versus multi-variable calibration (streamflow and SWE). Model results showed that the gridded ERA5 data was the best climate input for driving the SWAT model in PRB. A modified SUFI2-SWATCUP method to automatically remove unrealistic snow parameter combinations outperformed the standard SUFI2-SWATCUP, and it significantly reduced the total number of simulations. Compared with single-variable calibration using streamflow, an automatic multi-variable calibration using streamflow and SWE was shown to effectively limit the uncertainty of snow-related parameters and provide better prediction of snow-affected spring streamflow. The framework developed in our study can help reduce uncertainties in the hydrological modeling of large-scale, regulated, and snow-dominated watersheds in higher latitudes and can help the development of reliable strategies for water resources planning and management.