Research provides new insight on mountain glacier–derived water resource systems, impacting up to 1.9 billion people globally.

Scientists from around the world have assessed the planet’s 78 mountain glacier-based water systems and, for the first time, ranked them in order of their importance to adjacent lowland communities, as well as their vulnerability to future environmental and socioeconomic changes. These systems, known as mountain water towers, store and transport water via glaciers, snow packs, lakes, and streams, thereby supplying invaluable water resources to 1.9 billion people globally—roughly a quarter of the world’s population.

The research, published in the prestigious scientific journal Nature, provides evidence that global water towers are at risk, in many cases critically, due to the threats of climate change, growing populations, mismanagement of water resources, and other geopolitical factors. Further, the authors conclude that it is essential to develop international, mountain-specific conservation and climate change adaptation policies and strategies to safeguard both ecosystems and people downstream.

Most vulnerable water tower

According to the research, the most relied-upon mountain system globally is the Indus water tower in Asia. The Indus water tower—made up of vast areas of the Himalayan mountain range and covering portions of Afghanistan, China, India, and Pakistan—is also one of the most vulnerable. High-ranking water tower systems on other continents are the southern Andes, the Rocky Mountains, and the European Alps.

The research is presented at a press conference that took place on 9 December 2019 during the American Geophysical Union (AGU) Fall Meeting 2019 in San Francisco, USA.

Reliance and vulnerability

To determine the importance of these 78 water towers, researchers analyzed the various factors that determine how reliant downstream communities are upon the supplies of water from these systems. They also assessed each water tower to determine the vulnerability of the water resources, as well as the people and ecosystems that depend on them, based on predictions of future climate and socioeconomic changes.

Of the 78 global water towers identified, the following are the five most relied-upon systems by continent:

  • Asia: Indus, Tarim, Amu Darya, Syr Darya, Ganges-Brahmaputra
  • Europe: Rhône, Po, Rhine, Black Sea North Coast, Caspian Sea Coast
  • North America: Fraser, Columbia and Northwest United States, Pacific and Arctic Coast, Saskatchewan-Nelson, North America-Colorado
  • South America: South Chile, South Argentina, Negro, La Puna region, North Chile

Unique research

The study, which was authored by 32 scientists from around the world, was led by Prof. Walter Immerzeel and Dr. Arthur Lutz of Utrecht University, longtime researchers of water and climate change in high mountain Asia.

“What is unique about our study is that we have assessed the water towers’ importance, not only by looking at how much water they store and provide, but also how much mountain water is needed downstream and how vulnerable these systems and communities are to a number of likely changes in the next few decades,” said Immerzeel.

“By assessing all glacial water towers on Earth, we identified the key basins that should be on top of regional and global political agendas,” Lutz added.


This press release was first published by Utrecht University.

Read more: Immerzeel, W. W. et al. 'Importance and vulnerability of the world’s water towers.' Nature (2019): https://doi.org/10.1038/s41586-019-1822-y.


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