River discharge simulation of a distributed hydrological model on global scale for the hazard quantification

Abstract

We introduce a global river discharge simulation system based on the BTOP models for individual river basins (Global BTOP) and apply Global BTOP to quantify flood and drought hazards globally. The BTOP model utilizes a modified topographic index and simulates runoff processes including snowmelt, overland flow, soil moisture in the root and unsaturated zones, sub-surface flow, and river discharge. The Global BTOP is constructed from available river network data on the 10-arcmin (about 20-km) grid in the current version. The BTOP model topographical features are obtained using river network upscaling algorithm that preserves 3-arcsec (about 90-m) HydroSHEDS and 30-arcsec (about 1-km) Hydro1K characteristics in order to reduce the impact of upscaled dataset to the discharge simulation. In the Global BTOP, the International Geosphere-Biosphere Programme (IGBP) land cover and the Food and Agriculture Organization of the United Nations (FAO) soil digital maps of the world are used for the root zone depth and soil properties, respectively. The long-term seasonal potential evapotranspiration are estimated by the Shuttleworth-Wallace model using climate forcing data CRU TS3.1 and a fortnightly Normalized Difference Vegetation Index (NDVI). The Global BTOP is run with globally available daily precipitation datasets and calibrated to the observed global and local river discharge data. From these preliminary calibration results, the Global BTOP has demonstrated good performance in selected river basins and can be utilized for many useful applications.