The Ganga river basin, India’s largest, experienced a record low in snow persistence in 2024, as observed by data from the International Centre for Integrated Mountain Development (ICIMOD). The Brahmaputra and Indus basins also saw similar declines, threatening water supplies for millions

What is Snow Persistence?

Snow persistence refers to the fraction of time snow remains on the ground. The melting snow provides essential water to people and ecosystems, especially in the Hindu Kush Himalaya (HKH) river basins, where it accounts for 23% of the annual runoff. The HKH mountains span approximately 3,500 km across eight countries and are crucial water sources for 10 major river systems in Asia, impacting nearly a quarter of the world’s population.

Key Findings of the Report

Data Analysis (2003-2024)

• The report analyzed snow persistence data from 2003 to 2024, revealing significant fluctuations in snow cover between November and April each year.
• The Ganga river basin recorded its lowest snow persistence in 22 years, 17% below the long-term average, surpassing the previous record low in 2018.
• The Brahmaputra basin saw snow persistence 14.6% below normal, slightly better than the 15.5% below normal in 2021.
• The Indus basin’s snow persistence dropped 23.3% below normal, though this was partly offset by excesses in lower altitudes.

Impact on Other Regions

• The Amu Darya basin in Central Asia recorded its lowest snow persistence in 2024, 28.2% below normal.
• The Helmand river basin saw persistence almost 32% below normal, breaking the 2018 record.
• The Mekong river basin was only slightly below normal.

Causes of Lower Snow Persistence in 2024

• Weak Western Disturbances: A primary cause was weaker western disturbances due to changing climate and global warming.
• High Sea-Surface Temperatures: Persistently high temperatures in the Mediterranean, Caspian, and Black Seas weakened and delayed western disturbances, reducing winter precipitation and snowfall.

Factors for Higher Snow Persistence

• Yellow River Basin: Snow persistence exceeded normal by 20.2% due to cold, dry air from Siberia and Mongolia interacting with moist air from the Pacific Ocean, resulting in snowfall over higher altitudes.

Importance of Snow Persistence in India

• Snowmelt contributes significantly to water availability in the Ganga (10.3%), Brahmaputra (13.2%), and Indus (around 40%) basins, versus lesser contributions from glacier melts.
• Reduced snow in 2024 could affect water availability, particularly in the Indus basin, if early-season rainfall is also low.

Long-Term Solutions and Recommendations

• Reforestation: Planting native tree species to help retain more snow on the ground.
• Improved Weather Forecasting: Enhanced forecasting and early warning systems can help communities prepare for water stress.
• Water Infrastructure and Policies: Developing better infrastructure and protective policies for snowfall areas is crucial.
• Community Involvement and Regional Cooperation: Engaging communities in decision-making and promoting regional cooperation are vital for sustainability.