The newly formed ‘Yarlung Zangbo-Brahmaputra River Basin Network’ seeks to strengthen transboundary cooperation to overcome significant challenges in the region and achieve sustainable development in the region.
Mountain peaks in the Hindu Kush Himalaya (HKH) region – usually capped in a white blanket of snow in the winter – remain noticeably bare this year, particularly in the western Himalayas. This winter has been very unusual, with little or no snowfall throughout the region. Farmers are understandably concerned, as low snowfall has a direct and severe impact on agriculture. This is particularly acute for the HKH region which is heavily dependent on agriculture.
Snow is an important source of livelihood in the mountain regions. Snow typically begins accumulating in October or November and continues through to March, particularly in the western HKH region. Snow cover usually acts as an insulating blanket, shielding dormant crops, allowing root growth, preventing frost penetration, and protecting soil from erosion. Reduced snowfall and erratic rains across the Himalayan region have the potential to cause adverse ecological impacts in the region, including on water and agroforestry.
2023/2024 – unusual winter
However, temperatures have been warmer than average this season – a likely reason for the below-normal snow cover.
Even if there is significant snowfall in February and March as temperatures start to rise, it will probably be too little, too late to make up for the existing deficit,” says Sher Muhammad, Cryosphere Expert at ICIMOD
The lack of sufficient snow accumulation means that when the snow melts later in the year, there will be less ‘runoff’ – excess water which flows across the surface of the land and into nearby water bodies. With fewer snowfall events, there will be less snow on the ground, with decreased snow depth, meaning that there will be less melted snow running into rivers and streams when the weather warms up. So less snowfall over time could substantially reduce water for agriculture when it's needed most.
Mounting concerns for farmers across the region
Mountain communities already face numerous challenges, including crop failure, livestock deaths, fodder shortages, loss of life and property due to disasters, and psychological distress. The extremely dry winter follows years of below-average snowpack accumulation and is expected to further strain water resources this spring and summer. With rivers fed by mountain runoff potentially running dangerously low, farmers may be unable to irrigate fields or sustain livestock. Food insecurity, economic losses, and migration could intensify without adequate adaptation measures. Examples from the region include:
Nepal: In Humla District, in north-western Nepal, the high-altitude Limi Valley saw a single unusual early snowfall event in late September but has since experienced a pronounced lack of precipitation.
We are very worried about the implications for agriculture and our mountain ecosystems. - Paljor, Ward Chairperson in Halji village.
Humla district, where the majority of people are farmers, falls within the western part of the Nepal Himalayas which depend on the ‘Western Disturbance’ for snow. Western Disturbance is an extra-tropical cyclone that develops in the Mediterranean, which brings sudden winter rain, sleet and snow to the HKH region, and maintains the flow of northern rivers.
Pakistan: The high-altitude region of Central Hunza in northern Pakistan would generally be metres deep in snow around this time of the year. However, the region has not seen a single snowflake this winter, which has been warmer than usual.
Winters are being pushed later into spring, meaning we may see snowfall in April or May, or even no snowfall at all some years. These changes could lead to drought, severely affecting agriculture and drinking water supplies in the region - Zarina Baig, Climate researcher, resident in Hunza.
Contributing factors to the low snowfall
Global heating, a major facet of the climate crisis, is influencing various weather phenomena on both regional and global scales. Although the precise physical mechanisms are not fully understood, it is believed to contribute to prolonged and more intense La Niña – El Niño conditions. These disruptions in normal weather patterns, in turn, impact the 'Western Disturbance,' a meteorological phenomenon with a significant influence on the hydrological regime of the Hindu Kush Himalaya. Consequently, this dynamic interplay affects the water security of the region's population.
An exceptionally dry winter could mean heavy snowfall in spring, which could bring catastrophes like avalanches and flash floods. We are moving headfirst into the reality of 1.5 degrees global temperature; what we are experiencing here is just a snippet of what is to unfold. Urgent action is required to build the resilience of Himalayan communities in the face of snow drought and its cascading impacts. Arun Shrestha, Senior climate change specialist, ICIMOD.
Observed past temperature trends shows a steady rise: 2023 recorded the hottest global temperatures. The average temperature worldwide was 1.5°C above pre-industrial levels according to climate data (ECMWF ERA5 datasets & JRA-3Q dataset). Every day in 2023 surpassed 1°C above temperatures from 1850 to 1900. June through August were also the hottest summer months ever recorded. From 2022 to 2023, global temperatures notably increased over both land and oceans.
This record warmth is attributed to the persistently high Sea Surface Temperature globally. After three years of La Niña conditions (2020–2022), April 2023 saw a switch to El Niño (WMO). Marine heatwaves impacted the Mediterranean, Gulf of Mexico, Indian Ocean, North Pacific, and North Atlantic.
The Western Disturbance forms over the Mediterranean Sea, Caspian Sea, and Black Sea and moves eastwards, crossing Iraq, Iran, Afghanistan, and Pakistan before reaching northern and northwestern India and western Nepal. The Western Disturbance system plays a critical role for sustaining water for agriculture in the HKH region during winter.
What we understand is that temperature anomalies in 2023 have weakened and delayed the Western Disturbance, affecting winter precipitation, crop production, and snowfall in the western Himalayan region.
The consequences of the temperature anomaly in 2023 were observed in many parts of the HKH region. What we are experiencing is the reality of what 1.5 degrees means for the HKH
Understanding what drives the Western Disturbance and how it is changing is key to predicting snowfall in the Himalayas. It has become even more crucial for the science and decision-making processes to move in parallel. Tracking these changes and using this information to forecast potential impacts on water availability in the highlands and downstream is significant for addressing associated risk. This points to the need for advancing the science of monitoring the influence of the Western Disturbance on snowfall in the region, as this is a topic that is not well understood particularly among decisionmakers.
Implications for glaciers in the HKH: The Western Disturbance serves as the main source of snowfall that nourishes the HKH glaciers, particularly glaciers in the western part of the region, while for eastern Himalayan glaciers, summer precipitation is the main source. These glaciers play a crucial role in feeding major rivers such as the Ganga, Indus, and Brahmaputra, as well as numerous mountain springs and rivulets.
The 2023 annual climate summary report, as presented in the monthly Climate Bulletin of the European Centre for Medium-Range Weather Forecasts (ECMWF) in January 2024, summarises how El Niño – La Niña and Western Disturbance contributed to below-normal precipitation in the northern parts of India, Afghanistan, and Pakistan.
On average, annual snowmelt contributes approximately 23% of the flow of the 12 major river basins that originate high in the HKH and flow downstream to farmlands and cities, with snowmelt runoff from individual basins varying from 5 to 77%. The combination of seasonal snowmelt and glacial melt plays a key role in river hydrology and in daily life downstream. In addition, snow helps to sustain glaciers, while snow cover helps regulate the temperature of the earth’s surface, and variations in snow cover can affect regional weather patterns. The cooling associated with moist spring soils and a heavy snowpack in Eurasia is believed to shift the arrival of the summer monsoon season and influence its strength and duration.
Changing monsoon and prepping for the future: The region overall has been experiencing extended monsoons in recent years, characterised by high and intense rainfall. The 2023 monsoon in eastern Himalaya (east Nepal, Sikkim in India, Bhutan) resulted in disastrous flooding, accompanied by numerous landslides. Further north, noticeable changes have been occurring, including a shift in precipitation phases. Areas that traditionally experienced snowfall are now seeing more frequent rain.
While the data gap is still a major concern for the region, it has become paramount to make the most of existing data, and expediate uptake of adaptive measures to mitigate future risks. Decisions on water management need to be swift in adjusting to manage flood risk as well as water needs. To reduce future water stress and risk, adaptive measures must focus on optimising food production and enhancing irrigation networks, while promoting regional Disaster Risk Reduction strategies and leverage the trade-off between water and food security needs.