Snow is disappearing from the high Himalayas at a rate and in a pattern that is breaking centuries of established climate norms. A groundbreaking study by researchers from IIT-Jammu and IIT-Mandi, published in the journal Nature, confirms the grim reality long feared by local communities: snow droughts are becoming frequent, intense, and are systematically destabilising Asia's crucial water reservoir.
Alarming Data Points to a Worsening Crisis
The research, which analysed nearly two decades of high-resolution satellite data across the vast Hindu Kush Himalaya (HKH) region, found an alarming increase in snow drought events. These are winters marked by either drastically low snowfall or unusually rapid melting. The study recorded up to 25 such snow drought events in the upper Indus and Amu Darya basins between 1999 and 2016.
In critical river basins like the Ganga and Brahmaputra, traditionally snow-rich areas, researchers observed losses of up to 15 snow-covered days. Hemant Singh, a research scholar at IIT-Jammu, pointed out that the data clearly shows "moderate to severe snow droughts" in recent years like 2015 and 2016, with pronounced patterns in Afghanistan and northern India.
The team employed sophisticated new indices, including the Snow Water Equivalent Index (SWEI) and snow cover days (SCD), mapped at an unprecedented 500-metre resolution. This granular analysis provides the clearest picture yet of the accelerating snow depletion.
Lives and Livelihoods Already Feeling the Impact
The consequences are not abstract data points but are being lived daily by mountain communities. Tsering, a farmer from Ladakh, describes a new, unsettling pattern. "A new pattern has emerged," he said, recounting unseasonal snowfall in August damaging his barley crop, followed by bare peaks in winter. "There's less snow, and it doesn't stay," he added, a direct reflection of the shrinking snow cover duration found in the study.
Divyesh Varade, assistant professor at IIT-Jammu, explains the core problem: "Seasonal snow acts as a natural reservoir. When that shrinks, it affects everything from agriculture to hydropower and the timing of river flows." Spring meltwater, once a reliable source for irrigation, now arrives unpredictably, causing crops to ripen at the wrong time and leaving reservoirs underfilled.
A Fundamental Shift in Mountain Hydrology
The issue is deeper than just less snow. It represents a fundamental unwinding of the region's climatic logic. The HKH is warming faster than the global average—about 0.74°C higher—causing a critical shift at altitudes between 3,000 and 6,000 metres. Here, the balance is tipping from snowfall to rainfall.
Vivek Gupta of IIT-Mandi states bluntly, "Once this zone starts receiving more rain than snow, it fundamentally alters mountain hydrology." Rain runs off quickly, failing to provide the sustained, delayed melt that feeds rivers through the dry summer months. This dependency is stark in basins like the Indus and Helmand, where snowmelt contributes more to river runoff than glacial melt.
Sher Muhammad, a cryosphere specialist at ICIMOD, emphasised in the Nature article that focusing only on glaciers misses the more immediate threat: "Snowmelt is more significant in many places, and it's declining faster." His colleague, Qianggong Zhang, added that snow droughts can disrupt water availability far more abruptly than glacier melt, with even a week's delay in meltwater affecting crop yields in the western Himalayas.
The study identifies multiple hotspots, from the Amu Darya in the west to the Mekong in the east. Updated data confirms this is a current and worsening pattern. Despite the scale of the threat, the scientists note that seasonal snow loss remains glaringly absent from regional water policy frameworks. They urgently call for snow to be treated as a strategic water asset, with monitoring integrated into national strategies. As Gupta warns, "Every missing day of snow is a day less of stored water."
