ROLE OF GLACIERS IN INDIA'S WATER SUPPLY: A Comprehensive Technical Review of Himalayan Cryosphere Hydrology, Regional Water Security, and Climate-Driven Challenges

Abstract

Glaciers of the Hindu Kush–Himalayan (HKH) region constitute one of the largest repositories of freshwater outside the polar ice caps and serve as the foundational water towers for approximately 1.3 billion people in the Indian subcontinent. This paper presents a comprehensive technical review of the hydrological role of Himalayan and Karakoram glaciers in sustaining India's major river systems — including the Ganga, Indus, Brahmaputra, Yamuna, Beas, Satluj, and Chenab — with particular emphasis on quantifying their contribution to seasonal water availability, agricultural irrigation, domestic water supply, and hydroelectric power generation. The review synthesises findings from four decades of glaciological research, remote sensing studies, hydrological modelling, and field-based mass balance measurements from the Indian Space Research Organisation (ISRO), Wadia Institute of Himalayan Geology (WIHG), Space Applications Centre (SAC), and international collaborators including the International Centre for Integrated Mountain Development (ICIMOD). Inventory data indicate that India's glacierised area spans approximately 75,000 km², comprising an estimated 9,575 individual glaciers primarily distributed across Jammu & Kashmir, Ladakh, Himachal Pradesh, Uttarakhand, and Sikkim. The paper quantifies the contribution of glacier meltwater to river flow, which ranges from 20% to 70% during the pre-monsoon and dry-season months across different river systems, demonstrating that glaciers function as a critical seasonal buffer, releasing stored water precisely when monsoon rainfall is absent. In the context of accelerating climate change, which has caused measurable and statistically significant glacier retreat across the HKH region at rates of 8–22 metres per year since the 1980s, the paper evaluates the long-term trajectories of glacier mass balance under IPCC RCP 4.5 and RCP 8.5 scenarios, and assesses the downstream consequences for water security, food production, and hydropower capacity. A suite of adaptation strategies — including high-altitude water storage, managed aquifer recharge, artificial glacier programmes, and demand-side agricultural water efficiency improvements — is reviewed and evaluated. The paper concludes that the intersection of demographic water demand growth, agricultural intensification, and accelerating cryosphere degradation represents a water security crisis of continental scale requiring immediate, coordinated policy and infrastructure responses.