Application of satellite — based rainfall products and SRTM DEM in hydrological modelling of Brahmaputra basin

Hydrological modelling of large river catchments is a challenging task for water resources engineers due to its complexity in collecting and handling of both spatial and non-spatial data such as rainfall, gauge discharges, and topographic parameters. In this paper an attempt has been made to use satellite-based rainfall products such as Climatic Prediction Centre (CPC)-National Oceanic and Atmospheric Administration (NOAA) data for hydrological modelling of larger catchment where the limited field rainfall data is available. Digital Elevation Models (DEM) such as Global DEM (1 km resolution) and Shuttle Radar Topography Mission (SRTM) 3-arc second (90 m resolution) DEM have been used to extract topographic parameters of the basin for hydrological modelling of the study area. Various popular distributed models have been used in this study for computing excess rainfall, direct runoff from each sub-basin, and flow routing to the main outlet. The Brahmaputra basin, which is very complex both hydraulically and hydrologically due to its shape, size, and geographical location, has been examined as study area in this study. A landuse map derived from the satellite remote sensing data in conjunction with DEM and soil textural maps have been used to derive various basin and channel characteristics such as each sub-basin and channel slope, roughness coefficients, lag-time. Percentage of residual flows computed between observed flows and simulated flows using Global and SRTM DEMs are discussed. It is found that the topographic parameters computed using SRTM DEM could improve the model accuracy in computing flood hydrograph. Need of using better resolution satellite data products and the use of high-density field discharge observations is discussed.