A 1–10-Day Ensemble Forecasting Scheme for the Major River Basins of Bangladesh: Forecasting Severe Floods of 2003–07*

Abstract

This paper describes a fully automated scheme that has provided calibrated 1-10-day ensemble river discharge forecasts and predictions of severe flooding of the Brahmaputra and Ganges Rivers as they flow into Bangladesh; it has been operational since 2003. The Bangladesh forecasting problem poses unique challenges because of the frequent life-threatening flooding of the country and because of the absence of upstream flow data from India means that the Ganges and Brahmaputra basins must be treated as if they are ungauged. The meteorological-hydrological forecast model is a hydrologic multimodel initialized by NASA and NOAA precipitation products, whose states and fluxes are forecasted forward using calibrated European Centre for Medium-Range Weather Forecasts ensemble prediction system products, and conditionally postprocessed to produce calibrated probabilistic forecasts of river discharge at the entrance points of the Ganges and Brahmaputra into Bangladesh. Forecasts with 1-10-day horizons are presented for the summers of 2003-07. Objective verification shows that the forecast system significantly outperforms both a climatological and persistence forecast at all lead times. All severe flooding events were operationally forecast with significant probability at the 10-day horizon, including the extensive flooding of the Brahmaputra in 2004 and 2007, with the latter providing advanced lead-time warnings for the evacuation of vulnerable residents.

GloFAS – global ensemble streamflow forecasting and flood early warning

“…Several flood forecasting systems are based on observed river level, while future values are extrapolated through river routing models or by coupling observed rainfall fields into hydrological models. The extension of the forecast horizon beyond the response time of a river basin is enabled by the use of numerical weather predictions (NWPs) as input to hydrological-hydraulic models (e.g., He et al, 2010;Hopson and Webster, 2010;Paiva et al, 2012;Thiemig et al, 2010). Recent review articles by Cloke and Pappenberger (2009) and by Alfieri et al (2012a) showed the strong potential of using ensemble NWPs to further extend the forecasting horizon in early warning systems.…”

Assessment of the weather research and forecasting model generalized parameterization schemes for advancement of precipitation forecasting in monsoon‐driven river basins

“…The problem is critical in the transboundary or international river basins where it is almost impossible to obtain reliable precipitation data from the upstream regions in near realtime due to hydropolitical issues [Hopson and Webster, 2010;Hossain et al, 2007;Hossain and Katiyar, 2006]. A report by UN-Water [2008] shows that 40% of the global population resides in the 263 transboundary or International River basins.…”

Can a multi-model approach improve hydrological ensemble forecasting? A study on 29 French catchments using 16 hydrological model structures

“…Uncertainties from the structure of the hydrological model, i.e., in the mathematical representation of the hydrological processes involved in the rainfall-runoff transformation, were however not considered. An operational forecasting system that takes into account model uncertainty is presented by Hopson and Webster (2010) for the Brahmaputra and Ganges Rivers. It is based on the ECMWF 51-member ensemble prediction system and two hydrological models (semi distributed and lumped).…”