Mapping and Assessing Glacial Lakes in Pakistan: Risk Insights from NDWI

Abstract

Water is essential for life, but it also brings serious risks, especially through water-related disasters. Over the past two decades, about 74% of natural disasters have been water-related, affecting millions worldwide. Glaciers are vital sources of freshwater for drinking, farming, industry, and hydropower. However, melting glaciers accelerated by climate change are forming unstable glacial lakes that can burst and cause Glacier Lake Outburst Floods (GLOFs), posing serious threats to downstream communities. This study focuses on five major river catchments in northern Pakistan: Hunza, Gilgit, Shyok, Astore, and Chitral. These areas have extensive glaciation and important hydropower infrastructure, making them especially vulnerable to GLOFs. Using satellite images from 2015 to 2020, we applied the Normalized Difference Water Index (NDWI) a technique that highlights water bodies using satellite data to map and monitor glacial lakes. An automated method helped identify around 1,500 glacial lakes, covering a total area of 62.25 km². Out of these, 36 lakes were classified as potentially hazardous. Most lakes (82%) are small, under 0.05 km², and lie at elevations between 3,400 and 5,100 meters, with the highest concentration (43%) between 4,000 and 4,500 meters. The study did not include en-glacial or sub-glacial lakes, as they require ground-based tools/equipment to detect. This research offers valuable baseline data for understanding glacial lake hazards in Pakistan. It emphasizes the need to include GLOF risk in national and regional planning and supports future efforts in hazard modeling and disaster risk reduction strategies.