Change detection of glaciers and snow cover and temperature using remote sensing and GIS: A case study of the Upper Indus Basin, Pakistan

Glaciers and snow cover in the Himalayas, Karakoram, and Hindu-Kush (HKH) mountain ranges are expected to decrease, resulting in serious consequences in terms of water availability for downstream population. This study is an attempt to detect temporal trend of snow cover in the Upper Indus Basin (UIB), in northern Pakistan, with respect to temperature change, spatial variation in land surface temperature, and to evaluate the accuracy of Landsat imagery for detecting land surface temperature. Landsat images, acquired for the period 1993 to 2019 and the Normalized Difference Snow Index (NDSI), were used to map the snow cover. Maximum snow cover of about 20,675 km² was observed in April 2017 followed by 1996, and 1999, when it was about 18,800 km²; the minimum of about 14,500 km² was recorded in April 1993, 2011 and 2018. The results show that there has been a very slight increase in snow cover area with time. The maximum elevation of snow-covered area, extracted from the Digital Elevation Model of Shuttle Radar Topography Mission (SRTM DEM) in the study area, is 7889 m while the minimum elevation is 991 m. Freezing temperature occurs above 3000 m elevation, indicating that these areas are covered by snow and glaciers for much of the year. Temperatures, of −20 °C to −25 °C, were present only at a few places–at the very high elevation of above 6000 m. We found inconsistencies in the Landsat temperature data, which were corrected using in-situ daily temperature data. Validation of Landsat extracted temperatures before and after using the in-situ daily temperature data improved the accuracy and removed the inconsistencies. We recommend use of in-situ diurnal temperature data to correct Landsat extracted temperature data.