Why in news? As per the Hindu Kush Himalaya snow update of the International Centre for Integrated Mountain Development (ICIMOD) report, the Ganga River basin — India’s largest — reached a record low snow persistence in 2024.The Brahmaputra and the Indus basins have suffered similarly, threatening water supply to millions of people.

What’s in today’s article?

• Hindu Kush Himalaya
• International Centre for Integrated Mountain Development (ICIMOD)
• Snow persistence
• Key highlights of the report
• What explains the lower and higher snow persistence in 2024?
• Way forward

Hindu Kush Himalaya

• 
• About
  • The Hindu Kush Himalaya (HKH) region is a vast mountain area that stretches across eight countries: Afghanistan, Bangladesh, Bhutan, China, India, Myanmar, Nepal, and Pakistan.
  • This region is often called the "Third Pole" because it contains the largest amount of ice and snow outside of the polar regions.
• Source of 10 large Asian river systems
  • It is the source of ten large Asian river systems – the Amu Darya, Indus, Ganges, Brahmaputra, Irrawaddy, Salween, Mekong, Yangtse, Yellow River, and Tarim.
  • The basins of these rivers provide water to 1.9 billion people, a fourth of the world’s population.
• Snow covered area
  • A considerable volume of water resources is stored as snow and glacier ice in the HKH.
  • Cryosphere components including permafrost and glacial lakes provide various ecosystem services for mountain and downstream communities.
• Indian areas in HKH region
  • Entire territory of 11 mountain states/UTs (Jammu & Kashmir (Indian administered area), Uttarakhand, Himachal Pradesh, Assam, Manipur, Meghalaya, Mizoram, Nagaland, Sikkim, Tripura, Arunachal Pradesh), & Darjeeling district of West Bengal state lies in HKH region.

International Centre for Integrated Mountain Development (ICIMOD)

• ICIMOD is a regional intergovernmental learning and knowledge-sharing center.
• Established -It was established in 1983 with its headquarters in Kathmandu, Nepal.
• Member Countries - It serves eight member countries in HKH region: Afghanistan, Bangladesh, Bhutan, China, India, Myanmar, Nepal, and Pakistan.
• Focus Areas
  • Climate Change and Environmental Sustainability: Monitoring climate change impacts and promoting adaptive measures.
  • Livelihoods and Poverty Reduction: Supporting sustainable livelihoods and reducing poverty in mountain communities.
  • Ecosystem Management: Promoting the sustainable management of mountain ecosystems.
  • Water Resources: Ensuring sustainable management and use of water resources.
  • Disaster Risk Reduction: Enhancing resilience to natural disasters in the region.

Snow persistence

• About
  • Snow persistence refers to the duration of time that snow remains on the ground in a specific area.
  • It is a measure of how long snow cover is present during a given period, typically over a season or year.
  • Snow persistence is an important indicator in various fields, such as hydrology, climatology, and ecology, as it influences water availability, climate patterns, and ecosystem health.
• Factors Influencing Snow Persistence
  • Temperature: Warmer temperatures lead to faster melting of snow, reducing snow persistence.
  • Precipitation: The amount and type (snow vs. rain) of precipitation.
  • Elevation: Higher elevations typically have longer snow persistence due to cooler temperatures.
  • Vegetation: Dense vegetation can insulate snow, slowing its melt and increasing persistence.
  • Topography: The shape and slope of the land can influence how snow accumulates and melts.

Key highlights of the report

• The authors of the 2024 HKH snow update analysed data from 2003 to 2024.
• They found significant fluctuations in snow persistence between November and April every year, when snow accumulates above ground.
• Snow Persistence Trends in India (2024)
  • Ganga River Basin:
    • Lowest in 22 Years: 17% below long-term historical average
    • Previous Record (2018): 15.2% below normal
    • High (2015): 25.6% above normal
  • Brahmaputra River Basin:
    • 2024: 14.6% below normal
    • Worse(2021): 15.5% below normal
  • Indus River Basin:
    • 2024: 23.3% below normal
    • Offset: Excesses in lower altitudes
  • Implications
    • Crucial for rivers like Ganga
      • Snow persistence is crucial for the Ganga River basin as its melt contributes 10.3% of the water, compared to 3.1% from glacier melts.
      • In the Brahmaputra and Indus basins, snowmelt provides 13.2% and around 40% of the water, respectively, versus 1.8% and 5% from glaciers.
    • Regional Impact: Significant reductions in snow persistence are expected to have a lasting effect on water supply for millions of people.
    • Downstream Effects: These changes threaten water availability and agriculture in downstream regions.

What explains the lower and highersnow persistence in 2024?

• Lower snow persistence
  • Weak Western Disturbances: Identified as the main cause for lower snow persistence in 2024.
    • It originates in Mediterranean Sea and brings rain and snow to the HKH region in winter.
    • However, high sea-surface temperatures in the origin regions weakened and delayed these disturbances, reducing winter precipitation and snowfall.
  • Changing Climate and Global Warming: Increasing instability in weather patterns.
  • Exacerbation by La Niña–El Niño: Prolonged and intense phases significantly influence global weather patterns, including western disturbances.
• Higher snow persistence - Snow persistence in the Yellow River basin was 20.2% above normal in 2024.
  • East Asian Winter Monsoon: Brings cold, dry air from Siberia and Mongolia.
  • Interaction with Moist Air: Cold air interacts with moist air from the Pacific Ocean. As a result, there was snowfall over higher altitudes in the upper Yellow River basin and eastern Himalaya.

Way forward

• Experts suggest that reforestation with native tree species can help the ground retain more snow.
• Improved weather forecasting and early warning systems can help local communities prepare for water stress.
• Better water infrastructure and policies to protect snowfall areas are also essential.
• Involving communities in decision-making and promoting regional cooperation are vital for sustainability.
• Reducing emissions is crucial to mitigate increasing sea-surface and ground temperatures, which lower snow persistence.
• Emphasizing the need for political will, experts highlighted the importance of cutting fossil energy consumption and production, especially among G-20 countries, which account for 81% of all emissions.