Morphometric Analysis of Gilgit River Basin in Mountainous Region of Gilgit-Baltistan Province, Northern Pakistan

摘要

Watershed morphometric analysis of a basin is key to understand the hydrological processes. The Gilgit river basin is situated in the Hindu Kush and Karakoram Mountains of Pakistan. The provincial capital of Gilgit-Baltistan is located in the lower part of the basin. Morphometric evaluation of the Gilgit river basin was carried out to study its drainage characteristics and overall water resource potential. The entire Gilgit river basin has been divided into six sub-basins to calculate and analyze the selected morphometric parameters. Morphometric parameters have been classified into linear, aerial and relief aspect. Geographic Information System (GIS) provides a viable method to extract and evaluate the characteristic of hydrological response behaviour of the basin. In the present study the utilization of remote sensing data such as Thermal Topography Mission and Global Elevation Model (ASTER-GDEM), Sentinel 2A image, coupled with geological and field data into GIS environment for morphometric analysis of Gilgit Basin. The drainage area of the basin is 13,538 km2 and shows a dendritic drainage pattern for all sub-basins. The analysis reveals that drainage network of entire Gilgit river basin constitutes a 7th order basin. Out of six sub-basins, Gilgit-Gahkuch (B1), Ishkoman (B2) and Phunder (B4) are 6th order sub-basins. Yasin (B3) and Gupis (B5) are 5th order sub-basins, while Bagrot (B6) is a 4th order sub-basin. The Gilgit Basin drainage density value is 0.50 km/km2, which indicates a well-drained basin. Morphometric parameters like stream number, order, length, bifurcation ratio, drainage density, stream frequency, elongation ratio, circularity ratio, form factor, relief and relative relief, slope, length of overland flow, ruggedness number, and hypsometric integral are calculated. The results indicate that the entire drainage basin area reflects youthful to early mature stage of the fluvial geomorphic cycle and high potential of stream discharge which is dominated by high relief, rainfall, glacier and snow fed order streams.