Effects of grid-size on effective parameters and model performance of SHETRAN for estimation of streamflow and sediment yield

ABSTRACT

For physically based spatially distributed models which rely on a grid based representation of the spatial variability in a river basin, choice of an appropriate grid-size without compensating model performance is important. The present study examines the effect induced by three different grid-sizes (1, 2 and 4 km) on the model parameter values and performance in simulating streamflow and sediment yield using the SHETRAN model applied to a humid tropical river basin, Netravathi. First, the effective calibrated parameters of a 2 km model were applied to the 4 and 1 km model and the model performance was assessed. This indicated good monthly streamflow simulations at both grid sizes and a poor sediment yield simulation at 4 and 1 km, which demanded a recalibration. It has been observed that the grid size has a significant effect on various parameters. The effect of the finer grid-size was on reduction in sediment parameter values, mainly overland and channel erodibility coefficient, which were found to generate the most sensitivity for sediment yield. Further, the statistical indices (NSE, R and PBIAS) after recalibration of the model with 1 km grid resolution were significantly improved. Hence, for the catchment under study, considering the model prediction accuracy (both streamflow and sediment yield) and the execution time, a 1 km grid-resolution is most appropriate.

KEYWORDS:

• River basin
• grid-size
• sediment yield
• distributed hydrologic model
• SHETRAN
• sensitivity analysis

Acknowledgements

The authors acknowledge Directorate of Economics and statistics, Karnataka, India and India Meteorological Department for sharing rainfall and metereological data for this study, Central Water Commission for providing streamflow and sediment discharge data, Dr. Birkinshaw, School of Civil Engineering and Geosciences; Newcastle University, UK for the great assistance in clearing all SHETRAN related queries. Authors are thankful to the Editorial board for constructive comments that significantly improved the paper.

Disclosure statement

No potential conflict of interest was reported by the author(s).