Irfan et al. /Int.J.Econ.Environ.Geol.Vol. 11(2) 19-24, 2020 19 c Using Multi-Mission Satellite Elevation Data for Delineation of Gilgit Watershed in Pakistan in Geographical Information Technology Environment Muhammad Irfan 1 , Muhammad Shafiq 2 , Mehrab Khan 1 1 Department of Earth and Environmental Science, Bahria University Karachi, Pakistan 2 Space and Upper Atmosphere Research Commission, SUPARCO Road, Karachi, Pakistan *Email: m.shafiq.meteo@gmail.com Received:17 January, 2020 Accepted:02 July, 2020 Abstract: The hydro-climatological variations in Gilgit watershed of Upper Indus basin is less scientifically understood due to diverse geography, remoteness of the region and larger variations in climatic conditions. Extraction of catchments at multiple scales is an important task in undertaking the watershed management studies. Satellite remote sensing (SRS) and geographical information technology (GIT) provide a very useful method to study the watersheds. In view of the facts, watershed/ natural resources management in Gilgit river basin, application of geospatial techniques to various elevation datasets is required in order to obtain more accurate results using these elevation datasets. To achieve this goal, the topographic feature extraction has been studied in the catchment of Gilgit river using different Digital Elevation Models (DEMs) viz., SRTM, ASTER GDEM and GTOPO30. Several small watersheds for the Phakor, Karamber, East Gammu, Bhort and Bad-e-Swat glaciers were delineated for the basin definition. The delineated watersheds have been visually analyzed against the optical Landsat 8 OLI imagery for mountainous ridge matching. The results revealed that, SRTM 30m (radar based) exhibited more accuracy among these DEMs because of its precise delineation in the Gilgit sub-basin. However, it is appropriate to say that computed area from all three DEMs generally show close agreement. This study is a good contribution towards better understanding of the watershed management and the hydrological responses in Gilgit watershed of the upper Indus catchment. Keywords: Gilgit, glacier, sub-basin, watershed, catchment, remote sensing, geoinformatics. Introduction The typical profile of any basin drainage, quantitatively, can be investigated by calculations of linear, relief and aerial aspect (Pareta and Pareta, 2011). Drainage morphology of basin as well as sub- basins in various parts of the earth has been assessed via geomorphologic conventional approaches (Rai et al., 2017). Geographical information technology (GIT) / geographical information system (GIS) approaches with different satellite data have allowed the feasible stage for analyzing morphometric factors and topography of a drainage network (Wakode et al., 2013). Morphometric study of drainage network is very useful and feasible in assessment of hydro- climatological variations, flood risk management, watershed management and water resource potential (Ahmad et al., 2018). However, it is difficult to study all drainage networks through ground observation or from survey caused by their range all over uneven terrain in the massive region particularly in rocky areas (Huggel et al., 2002). Recognition of drainage system within basin as well as sub-basins can be accomplished using highly developed methods such as Digital Elevation Models (DEMs) including Shuttle Radar Topography Mission (SRTM) and Advanced Space- born Thermal Topography Mission and Global Elevation Model (ASTER-GDEM). These DEMs have been utilized to analyze drainage system, Gilgit basin area and micro-watershed boundaries delineation (Ali et al., 2017; Pareta and Pareta, 2014). Study area Gilgit watershed is an important source which is situated in the northern region of Pakistan. It lies between longitude 72°25'02'' E to 74°19'25'' E and latitude 35°46'05'' N to 36°51'16'' N (Fig 1). The geographical watershed area is 13,552 sq.km and elevation varies between 1388 to 6722 m (Ali et al., 2017; 2019). The area altitude distribution and hypsography of the Gilgit watershed is shown in Figure 1. The glaciers are mainly distributed between 3500 to 5500 meters of elevation. The study area contains six major valleys including Gupis, Puniyal, Phandar, Gilgit, Ishkoman and Yasin. Moreover, three small rivers i.e., Phandar, Yasin and Ishkoman merge into Gilgit river (Ali et al., 2019; Mukhopadhyay and Khan, 2015). The hydro-climatological studies of the Gilgit region are sparsely found in the published articles and bibliography. The region is poorly gauged with only 5 meteorological stations in the region which include Gilgit, Gupis and WAPDA met stations at Shandure, Ushkore and Yasin (Adnan et al., 2017; Hasson et al., 2017). This station density is much lower than in technologically advanced countries as in Switzerland. There is one station per 475 square km for temperature and one per 100 square km for precipitation (Gubler et al., 2017). Due to remoteness of the region and larger variations in climatic conditions, northern region is scientifically under- explored. The glacier inventory of Pakistan (2017) developed by SUPARCO mentions that there are 979 Copyright © SEGMITE Open Access ISSN: 2223-957X Int. J. Econ. Environ. Geol. Vol. 11 (2) 19-24, 2020 Journal home page: www.econ-environ-geol.org