Hydro-morphometry of a trans-Himalayan River basin: Spatial variance, inference and significance

Abstract

Subansiri is the largest tributary of the Brahmaputra River basin originated in the Tibet Autonomous Region of China. After flowing about 160 km as Chayul Chu in Tibet, it runs as Subansiri in Arunachal Pradesh state of India for about 360 km before merging into the Brahmaputra River in Assam (India). This study was carried out to understand the hydro-morphometry of the entire Subansiri Basin comprising of three sub-basins: Chayul Chu, Upper Subansiri and Lower Subansiri. Geomorphometric parameters were extracted from Shuttle Radar Topographic Mission (SRTM) Digital Elevation Model of 30 m spatial resolution using Google Earth Engine and GIS software. On comparison, significant difference and spatial variation have been noticed in various morphometric parameters of the sub-basins. Notable differences are observed in some key morphometric parameters such as drainage density, stream frequency, constant of channel maintenance, infiltration number, drainage ratio, drainage texture, dissection index, ruggedness number, form factor ratio, elongation ratio etc. Hypsometric analysis has highlighted further the difference in geomorphic fabric, terrain maturity and hydrologic characteristics of these different sub-basins. Hydro-morphometric parameters have direct bearing on the hydrology. Thus, outcome of this study will be useful in water resources management and in finding engineering solutions to hydro-hazards for this basin and other basins worldwide.