Author(s): Biswa Bhattacharya, Maurizio Mazzoleni, Liton Chandra Mazumder

Linked Author(s): Biswa Bhattacharya, Maurizio Mazzoleni

Keywords: Uncertainty; Hydrological model; Rating curve; Brahmaputra;

Abstract: Uncertainty is inherent in any hydrological prediction. This uncertainty arises from errors introduced during modelling from a variety of sources, such as parameters, modelling formulation (structural) and measurements. Uncertainties in hydrological models can further be due to errors in discharge data used in calibration, which often is estimated from a rating curve based on measured stage at the outlet of the catchment. Errors in rating curve influence the calibration, and as a result uncertain model parameters may be obtained. This research focused on studying the influence of uncertain downstream boundary condition on the estimation of hydrological model parameters for the Brahmaputra basin. Due to the limited availability of data, remote sensing product of precipitation (TRMM) and global datasets of evapotranspiration and temperature were used to represent the spatio-temporal hydrological variability within the catchment. A semi-distributed hydrological model was implemented using the HEC-HMS software. The model was calibrated using the discharge data from a rating curve at the downstream boundary. In order to account for the uncertainty in the rating curve, an ensemble of fifty rating curves was generated from the measured stage-discharge data and for each of them the hydrological model was calibrated separately. Only a few model parameters were selected based on the previous sensitivity analysis. The outcome was a set of realisations of model parameters corresponding to the sampled rating curves. Finally, the simulated hydrographs probabilistically represented the simulated discharge inside the basin and represented the influence of the boundary condition on model uncertainty. The results of this study showed that the semi-distributed hydrological model was capable to properly represent hydrological dynamics in the Brahmaputra basin. It was further observed that the uncertainty was high particularly during the wet season.

DOI: https://doi.org/10.3850/38WC092019-0559

Year: 2019