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 per cent, while the highest snow persistence of 25.6 per cent was recorded in 2015.

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 per cent 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 per cent of river flow to the Amu Darya; 77 per cent of the Helmand’s flow; and 40 per cent 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 per cent below normal. Its previous lowest level was in 2018, when it saw a 42 per cent reduction. In addition, the Indus Basin has fallen to 23.3 per cent below normal, marking the lowest level in the past 22 years. The previous lowest year for this Basin was 2018, with a 9.4 per cent shortfall. The lowest variation from normal snow persistence this year was the Mekong basin where snow persistence was around 1 per cent below normal.

Wake-up call

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

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 per cent, while the highest snow persistence of 25.6 per cent was recorded in 2015. The current year has shown the lowest snow persistence, with a value of 17 per cent, which sharply contrasts between the southern and northern sides.

Notable decrease

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

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 per cent reduction. Conversely, in 2008, the changes in snow persistence reached its highest level, peaking at 32.1 per cent, suggesting a significant increase in snowfall during that period. The current year exhibits the lowest snow persistence, with 28.2 per cent 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.

The Helmand River basin experienced a remarkably low snow persistence during the 2018 season, significantly below the average by a margin of 41.9 per cent. 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 per cent. This year stands as the second lowest in terms of snow persistence, with a decrease of 31.8 per cent below normal levels and some spatial variations on the western side.