View over countryside from historic medieval town of Trujillo, Caceres province, Extremadura, Spain.

The countryside near Trujillo, Spain. People in dry lowland areas are likely to draw increasing amounts of water from nearby mountains. Credit: Geography Photos/UIG via Getty

Hydrology

Human thirst set to draw down mountains’ water banks

One-quarter of the global lowland population could depend on water from higher elevations by mid-century.

More than one billion people could depend on water flowing from mountain areas by the middle of the twenty-first century — a looming challenge to sustainable development and water management.

Global water consumption has almost quadrupled over the past 100 years, thanks to soaring population growth and food demand. As a result, people living in lowland areas have become increasingly dependent on runoff from hills and mountains to meet their freshwater needs.

Daniel Viviroli at the University of Zurich in Switzerland and his colleagues used a global hydrology and water resources model to project regional freshwater demand and availability under different socio-economic conditions. In a ‘middle of the road’ scenario, around 1.5 billion people — about one-quarter of the world’s lowland population — could depend on water flowing from mountain areas by mid-century. This is an increase from 200 million in the 1960s.

Densely populated lowlands in South and East Asia, particularly the Ganges–Brahmaputra–Meghna, Indus and Yangtze river catchments, are among regions most at risk of heavy reliance on mountain water, the authors found.