What are the findings of the 2024 Hindu Kush Himalayas snow update? | Explained

Record low snow persistence in Hindu Kush Himalaya threatens water supply, highlighting urgent need for climate action.

The story so far:

The Ganga river basin — India’s largest — reached a record low snow persistence in 2024, the Hindu Kush Himalaya snow update of the International Centre for Integrated Mountain Development (ICIMOD) has reported. The Brahmaputra and the Indus basins have suffered similarly, threatening water supply to millions of people. “Tragically this is yet another postcard from the frontlines of a climate crisis that is accelerating even beyond scientists’ projections and causing huge challenges in one of the most populated regions of the world,” Miriam Jackson, Cryosphere Lead at ICIMOD and a contributor to reports of the UN Intergovernmental Panel on Climate Change, told The Hindu.

Snow persistence is the fraction of time snow is on the ground. When this snow melts, it provides water to people and ecosystems. In the river basins of the Hindu Kush Himalaya (HKH), snowmelt is the biggest source of water in the streams. Overall, it contributes 23% of the runoff to the region’s 12 major river basins every year. The HKH mountains extend around 3,500 km over eight countries — Afghanistan, Bangladesh, Bhutan, China, India, Nepal, Myanmar, and Pakistan. These mountains are also called the “water towers of Asia” because they are the origins of 10 crucial river systems on the continent — Amu Darya, Indus, Ganga, Brahmaputra, Irrawaddy, Salween, Mekong, Yangtse, Yellow river, and Tarim. These river basins provide water to almost one-fourth of the world’s population and are a significant freshwater source for 240 million people in the HKH region.

The authors of the 2024 HKH snow update analysed data from 2003 to 2024 and found significant fluctuations in snow persistence between November and April every year, when snow accumulates above ground. Based on this, they made grim predictions of lasting impact on the people in the region as well as those downstream of the river basins.

In India, snow persistence in the Ganga, the Brahmaputra, and the Indus river basins dropped significantly in 2024. The Ganga river basin noted its lowest snow persistence in 22 years, 17% below the long-term historical average (also known as ‘normal’). The previous holder of this dubious distinction was 2018, when it was 15.2% below normal. In 2015, on the other hand, snow persistence was 25.6% above normal.

Similarly, snow persistence in the Brahmaputra basin was 14.6% below normal in 2024. It was worse in 2021, when the average persistence was 15.5% below normal. In the Indus river basin, snow persistence fell 23.3% below normal this year although this was offset by excesses in parts of the lower altitudes.

Outside India, the basin of the Amu Darya river — which flows through Central Asia — recorded its lowest snow persistence in 2024: 28.2% below normal. The figure for the Helmand river, an important source of drinking water for Iran and Afghanistan, was almost 32% below normal in 2024, beating a record set in 2018. Persistence in the part where the Mekong river originates in the Himalaya was only slightly below normal this time. (This river’s delta is Vietnam’s “rice bowl”.)