Link to the report: https://lib.icimod.org/record/36512

Kathmandu, Friday 14 June 2024 – Snow persistence, the fraction of time snow remains on the ground, is significantly lower than normal in the Hindu Kush Himalaya this year, with serious implications for downstream communities’ water security.

Leading experts from the International Centre for Integrated Mountain Development (ICIMOD), which publishes the annual Snow Update Report, warn water management officials to initiate drought management strategies and pre-emptive emergency water supply.

Snowmelt is the source of approximately 23% of the total water flow of 12 major river basins that originate high in the HKH. But its contribution to water supply varies from river to river – representing 74% of river flow to the Amu Darya; 77% of the Helmand’s flow; and 40% of the Indus’ flow.

Monitoring shows snow levels almost a fifth below normal across the region this year, with figures falling dramatically in the west, where its contribution to water supply is highest.

Helmand river basin shows the most dramatic fall in persistence at 31.8% below normal. Its previous lowest level was in 2018, when it saw a 42% reduction. In addition, the Indus Basin has fallen to 23.3% below normal, marking the lowest level in the past 22 years. The previous lowest year for this Basin was 2018, with a 9.4% shortfall. The lowest variation from normal snow persistence this year was the Mekong basin where snow persistence was around 1% below normal.

“We’ve seen a pattern of decreasing amounts and persistence of snow across the Hindu Kush Himalaya, with 13 of the past 22 years registering lower than normal seasonal snow persistence,” said ICIMOD Cryosphere Specialist Sher Muhammad, author of the Snow Update Report 2024.

“This is a wake-up call for researchers, policymakers, and downstream communities: lower accumulation of snow and fluctuating levels of snow pose a very serious increased risk of water shortages, particularly this year.”

Miriam Jackson, ICIMOD’s Senior Cryosphere Specialist emphasized the need for proactive measures. “We encourage relevant agencies to take proactive measures to address possible drought situations, especially in the early summer, update plans to accommodate water stress, and to notify communities of the risks.

“Beyond that, it’s clear that governments and people in this region need urgent support to help them adapt to changes in snow patterns that carbon emissions have already locked in.

“And that G20 countries need to cut emissions faster than ever before to prevent even more changes that will prove disastrous to major population centres and industries that rely on snow-melt in the mountains.”

In the Amu Darya River basin, the percentage change in seasonal snow persistence previously reached its lowest point in the last twenty-two years in 2018, with a 17.7% reduction. Conversely, in 2008, the changes in snow persistence reached its highest level, peaking at 32.1%, suggesting a significant increase in snowfall during that period. The current year exhibits the lowest snow persistence, with 28.2% below normal. This assessment highlights the dynamic nature of seasonal snow in the region and emphasises the need for continued dissemination of snow information to better understand and manage the impacts of these long-term changes.

In the Brahmaputra River basin, the year 2021 experienced the lowest seasonal snow persistence, dropped well below average at 15.5%. The highest recorded snow persistence occurred in 2019, reaching 27.1%. This year, the current snow persistence is also notably below normal at 14.6%.

In the Ganges River Basin, there has been significant fluctuations in the past twenty-two years. Prior to 2024, the year 2018 had the lowest snow persistence at 15.2%, while the highest snow persistence of 25.6% was recorded in 2015. The current year has shown the lowest snow persistence, with a value of 17%, which sharply contrasts between the southern and northern sides.

The Helmand River basin experienced a remarkably low snow persistence during the 2018 season, significantly below the average by a margin of 41.9%. However, in stark contrast, the year 2020 showcased the highest snow persistence in the past twenty-two years, surpassing the average by a notable 44%. This year stands as the second lowest in terms of snow persistence, with a decrease of 31.8% below normal levels and some spatial variations on the western side.

In the Indus River basin, there was a notable decrease in seasonal snow persistence in 2018, with a deviation of 9.4% from the average. In contrast, the highest snow persistence above normal was recorded in 2020 with a value of 15.5%. However, this year, there has been a remarkable decrease in snow persistence, falling 23.3% below normal levels with some positive patterns on the southern sides mostly in the lower altitudes.

In the Irrawaddy River basin, the seasonal snow persistence fluctuates every year in the past twenty-two years. The changes remain below 15% except the year 2023 with above normal snow of 19.1%. In 2017, the snow persistence fell below the average by 12.5% which is the lowest in the past twenty-two years. This year’s snow persistence is slightly below normal with a value of 2.4% having significant spatial heterogeneity.

In the Mekong River basin, the variability in seasonal snow persistence has increased in the last few years. The most negative snow persistence was observed in 2021, falling below the average by 38.4%. The year 2019 and 2020 have witnessed a significant increase in snow persistence, surpassing the normal levels by 68.8% and 52.5% respectively. This year, the snow persistence is slightly below normal of 1.1%.

The Salween River basin has also experienced an increased heterogeneity in snow persistence over the past few years. Like the Mekong River Basin, the most notable decrease in snow persistence was observed in 2021, with a deviation of 28% from the normal levels. The year 2019 and 2020 have witnessed a significant increase in snow persistence, surpassing the normal levels by 30.6% and 35% respectively. Conversely, the current year has seen a slightly below normal snow persistence, average by 2.4%.

The Tarim River Basin witnessed a significant decrease in long-term snow persistence in the past twenty-two years. The trends in snow persistence over the past twenty-two years, with 2003 and 2006 displaying the most positive values, 26.6% and 28.5% respectively. Notably, this year, there is a significant decrease in snow persistence with a value of 27.8%, lowest in the past twenty-two years.

In the Tibetan Plateau, the year 2018 experienced the lowest seasonal snow persistency, reaching a value of 34.7%. Conversely, the highest snow persistence was observed in 2020, reaching 63.3%. This year, the snow persistence is below normal with a value of 14.8% and exhibits considerable spatial variability throughout the basin.

In the Yangtze River basin, the year 2017 experienced the lowest seasonal snow persistency, reaching a value of 27.9%. In contrast, the highest snow persistence was observed in 2008 with a remarkable increase of 50.6% above normal. The long-term trend in snow persistence is significantly negative with this year also showing 13.2% below normal.

In the Yellow River basin, the seasonal snow persistence reached its lowest point in 2015, remaining significantly below average with a deviation of 42.2%. Conversely, the highest snow persistence was observed in 2008, surpassing the normal levels by an impressive 74.5%. In 2024, the snow persistence remains above normal, exceeding the normal value by 20.2%.

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