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WATER POLITICS

Via ICIMOD, a new report on water, ice, society, and ecosystems in the Hindu Kush Himalaya:

The Hindu Kush Himalayan (HKH) region, covering more than 4.2 million km2 , encompasses the highest mountain ranges in the world and contains the largest volume of ice on Earth outside of the polar regions, as well as large expanses of snow. Spanning some 3,500 km in length from Afghanistan in the west to Myanmar in the east, and covering parts or all of Pakistan, India, China, Nepal, Bhutan, and Bangladesh, the HKH is home to unique cultures, highly diverse landscapes, and all of the world’s peaks above 7,000 meters. The region hosts all or parts of four global biodiversity hotspots supporting diverse flora and fauna – the Himalaya, the Indo-Burma, the Mountains of Central Asia, and the Mountains of Southwest China. The glacier- and snow-covered mountains of the HKH are an important source of water for 12 river basins, including 10 major (transboundary) rivers – the Amu Darya, Brahmaputra (Yarlung Tsangpo), Ganges, Indus, Irrawaddy, Mekong (Lancang), Salween (Nu), Tarim, Yangtse (Jinsha), and Yellow (Huang He) – that flow through 16 countries in Asia and provide freshwater services to 240 million people living in the HKH region and 1.65 billion downstream. …

Key findings

> Glaciers disappeared 65% faster in the 2010s than in the previous decade

> On current emissions pathways 80% of glaciers’ current volume will be gone by 2100

> Availability of water is expected to peak in mid-century and then decline

> Vulnerable mountain communities are already experiencing major adverse impacts: loss and damage to lives, property, heritage, infrastructure

> Floods and landslides are projected to increase

> Impacts on fragile mountain habitats are particularly acute

CRYOSPHERE

1. Major advances in HKH glacier monitoring and analysis made in recent years show a significant acceleration of glacier mass loss by 65% in the HKH (high confidence) and reversal from mass gain/ steady state to mass loss in the Karakoram (medium confidence). Glacier mass changes between the 1970s and 2019 in most areas of the HKH have now been quantified with increased accuracy. The rate of glacier mass loss increased by 65%, from an average of –0.17 metres water equivalent (m w.e.) per year for the period 2000–2009 to –0.28 m w.e. per year for 2010–2019 (high confidence). The most negative mass balances are observed in the eastern part of the HKH. The Karakoram region, previously known for stable regional mass balances, showed slight wastage of –0.09 ± 0.04 m w.e. per year during 2010–2019, indicating the end of the Karakoram Anomaly (medium confidence).

2. Snow cover extent has shown a clearly negative trend in the HKH region since the early twentyfirst century with a few exceptions including the Karakoram (high confidence). There has been a significant decrease in the seasonal snow cover during the summer and winter months, as well as a decline from mid-spring through mid-fall, indicating a seasonal shift (high confidence). Snow cover days generally declined at an average rate of five snow cover days per decade with most of the changes at lower elevation (high confidence). Snow cover is likely to experience an accelerated loss in the future under different global warming levels in the HKH (medium confidence).

3. Still very little is known about permafrost, but what is known points to a decrease in permafrost occurrence (medium confidence). There are few field observations of permafrost in the HKH, but existing measurements show changes in permafrost, and remote sensing confirms a decrease in permafrost cover in studied regions (medium confidence). Modelled results calculate a loss of about 8,340 km2 in permafrost area in the western Himalaya between 2002–2004 and 2018–2020; and a loss of about 965 km2 in the Uttarakhand Himalaya between 1970–2000 and 2001–2017. On the Tibetan Plateau, the area of permafrost degradation will increase, with most (about two-thirds) of the permafrost being degraded by 2071–2099 under high emissions scenarios.

WATER

1. With accelerated glacier melt, ‘peak water’ will be reached around mid-century in most HKH river basins, and overall water availability is expected to decrease by the end of the century (medium confidence). At higher elevations, an increase is expected (more melt or more rainfall). However, the variability from basin to basin is large, and due to the large uncertainty in future precipitation projections, our confidence in estimates of future discharge remains low. More confident projections of precipitation, snow water equivalent, as well as both evaporative and subsurface fluxes will be crucial to improving our ability to accurately determine future water availability in the HKH.

2. With a changing climate and heightened awareness of the increased exposure of livelihoods and infrastructure to hazards, the mountain hazard landscape has become increasingly multidimensional (high confidence). A number of different slow- (e.g. sedimentation and erosion) and fast-onset hazards (e.g. floods and glacial lake outburst floods [GLOFs]) are occurring in the same watersheds, frequently at the same time, and often also in a cascading manner, complicating our ability to implement early warning and adaptation measures. Future frequency and intensity estimates exist only for a limited number of hazards, with medium confidence in a likely increasing trend. Confidence in trends varies across hazards but is especially evident for slow-onset hazards related to glacier retreat as well as events associated with increasing heavy precipitation.

3. Water sources in the high mountains are important not only for livelihoods and other demands in the immediate vicinity but also for the distant downstream areas that are heavily reliant on meltwater originating from mountains for agricultural, domestic, and industrial uses (high confidence). Glacier and snowmelt provide a buffer for downstream irrigation demand in the spring season (high confidence), and it is very likely that the dependency on them will increase in future (medium confidence).

ECOSYSTEMS

1. The cryosphere of the HKH is an important source of water for maintaining ecosystem health, supporting biological diversity, and providing ecosystem services (very high confidence). This biodiversity-rich region – 40% of which is under protected area coverage – is characterised by interconnected and diverse ecosystems. Sixty percent of the region features seasonal cryosphere (snow, glacier, permafrost, and glacial lakes) – a major source of water and other ecosystem services (very high confidence).