Spatial Distribution of Contaminants in Glacial Streams and River Tributaries in the Ecologically Sensitive Regions of Gilgit Baltistan, Pakistan

The China-Pakistan Economic Corridor (CPEC) between China and Pakistan passes through the environmentally fragile region of the Himalayas−Karakorum−Hindukush (HKH). Surging human influence in the form of transportation and tourism may pose a potential threat to the socio-environmental sustainability especially, the water resources of the region. Therefore, it is important to evaluate the status and hydrogeochemistry of freshwater in mountainous catchments. For this purpose, water samples were collected from the Hunza, Gilgit, and Indus River Basins from 2019 to 2020. The physicochemical and biological characteristics of surface water were investigated using the water quality index (WQI), multivariate statistics, Piper diagram, and Gibbs plots. The results revealed high seasonal variability in the hydrochemistry of water samples in all basins. Heavy metals (HM) i.e., arsenic (As), and lead (Pb) were detected in more than 50% of total water samples, whereas cadmium (Cd) and mercury (Hg) were detected in less than 15% of total water samples. 82% of water samples collected during summer and 48% in winter were contaminated with bacterial contamination (Escherichia coli (E. coli) and total coliform (T. coli)). Piper diagram and Gibbs plot suggested that rock weathering and dissolution of carbonate rocks are the dominating factors controlling the chemistry of glacial streams and river water. The results of this study have important implications for policymakers, regulators, and practitioners involved in water and environmental management across CPEC.