Ladakh’s giant ‘rivers of ice’ are slowing as the mountains warm
New observations indicate that glaciers in Ladakh — often described as "rivers of ice" — are showing a slowdown in their flow as the surrounding mountains warm
Glacier slowdown has long-term implications for the Indus river basin, where glacial meltwater makes a significant contribution to river flows during summer
In the near term, increased melting can temporarily raise runoff, a phenomenon known as "peak water," but once glaciers lose a substantial share of their stored ice, meltwater contributions are projected to decline
The findings add to a wider body of research documenting accelerated glacier retreat across the Himalaya-Karakoram region
Peak Water — The Turning Point in Glacier-Fed River Flows
"Peak water" is the hydrological term for the point at which glacier meltwater runoff, having risen for years as a warming climate accelerates ice loss, reaches its maximum and then begins an irreversible decline as the glacier's ice reserves are depleted. Before peak water, more melting means more river flow; after it, shrinking glacier mass means less water is available for melt, even if temperatures keep rising.
Key Details
- Coined and used extensively in glaciology literature, including the IPCC's Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC, 2019)
- Peak water runoff can temporarily exceed a glacier's initial yearly runoff by 50% or more before decline sets in
- For the Upper Indus Basin, peak water has been projected to occur around 2045 (± 17 years) under a moderate-emissions (RCP 4.5) scenario in recent modelling studies
- Peak water is reached later in basins with larger glaciers and higher ice-cover fractions, meaning the Indus basin (heavily glacier-fed) reaches it later than smaller Himalayan sub-basins
A slowdown in Ladakh's glaciers is consistent with a basin approaching or past its peak water phase — a warning sign that the Indus basin's dependence on glacial melt for summer flows is entering a more precarious, declining-supply phase.
The Indus River System and the Indus Waters Treaty (1960)
The Indus basin is the most glacier-dependent of India's major Himalayan river systems, more so than the Ganga or Brahmaputra basins, because a larger share of its summer flow comes from snow and glacier melt rather than monsoon rainfall. This makes glacier health in Ladakh and the Karakoram directly relevant to water security debates governed under the Indus Waters Treaty.
Key Details
- The Indus Waters Treaty (1960), brokered by the World Bank, allocated the three Western Rivers — Indus, Jhelum, and Chenab — to Pakistan (with limited non-consumptive use permitted to India), and the three Eastern Rivers — Ravi, Beas, and Sutlej — to India
- The treaty created the Permanent Indus Commission, with a Commissioner from each country, to oversee implementation
- Glacier and snowmelt have greater hydrological importance for the Indus basin than for the Ganga or Brahmaputra basins, per glaciological assessments
Because glacial melt underpins a treaty-governed transboundary river system, long-term glacier decline in Ladakh has implications not just for local water availability but for the volumes of water flowing through the treaty framework.
National Mission for Sustaining the Himalayan Ecosystem (NMSHE)
NMSHE is one of the eight national missions under the National Action Plan on Climate Change (NAPCC), India's institutional response to monitoring and adapting to changes in the Himalayan ecosystem, including glacier dynamics.
Key Details
- NAPCC was launched in 2008 and comprises eight national missions, including NMSHE and the National Water Mission
- NMSHE is coordinated by the Department of Science and Technology (DST) and aims to build a knowledge base on Himalayan glaciers, biodiversity, and climate impacts, and to support Himalayan states with adaptation strategies
- The mission also promotes regional scientific cooperation among Himalayan countries on glacier and ecosystem monitoring
Long-term glacier monitoring of the kind that identifies a slowdown in Ladakh's glaciers falls within NMSHE's mandate to track and interpret changes in Himalayan cryosphere behaviour.
- The Parachik glacier in Ladakh has seen its retreat rate rise sharply — from an average of about 2 metres/year (1971–1999) to about 20 metres/year (2015–2021), per glaciological studies
- Upper Indus Basin peak water is projected around 2045 (± 17 years) under RCP 4.5
- Indus Waters Treaty (1960): Western Rivers (Indus, Jhelum, Chenab) to Pakistan; Eastern Rivers (Ravi, Beas, Sutlej) to India
- NAPCC (2008) comprises 8 national missions; NMSHE is coordinated by the Department of Science and Technology
- The Himalaya-Karakoram region is often termed the "Third Pole" for its concentration of glacial ice outside the polar regions