Mountains of the world, water towers for humanity: Typology, mapping, and global significance

Abstract

[1] Mountains are important sources of freshwater for the adjacent lowlands. In view of increasingly scarce freshwater resources, this contribution should be clarified. While earlier studies focused on selected river systems in different climate zones, we attempt here a first spatially explicit, global typology of the so-called ''water towers'' at the 0.5°Â 0.5°resolution in order to identify critical regions where disproportionality of mountain runoff as compared to lowlands is maximum. Then, an Earth systems perspective is considered with incorporation of lowland climates, distinguishing four different types of water towers. We show that more than 50% of mountain areas have an essential or supportive role for downstream regions. Finally, the potential significance of water resources in mountains is illustrated by including the actual population in the adjacent lowlands and its water needs: 7% of global mountain area provides essential water resources, while another 37% delivers important supportive supply, especially in arid and semiarid regions where vulnerability for seasonal and regional water shortage is high.

A Participatory Approach for Assessing Alternative Climate Change Adaptation Responses to Cope with Flooding Risk in the Upper Brahmaputra and Danube River Basins

“…Climate change will also decrease water availability in lowlands that are influenced by discharge from contiguous mountain (Messerli et al 2004). Relatively high mountain run-off can be found in semi arid and arid regions, such as the Himalayas, but also in some humid regions, such as the European Alps (Viviroli et al 2007). We can thus say that mountains are important for the hydrology of the lowlands, especially when lowlands are arid, as is the case with the Himalayas (Viviroli and Weingartner 2004;Messerli et al 2004).…”

Ecosystem Services: The Opportunities of Rewilding in Europe

“…Mountain ecosystems cover approximately 41 % of Europe's territory, providing various services due to their multifunctionality. Mountains are "water towers" as they provide water for multiple uses, including irrigation, human consumption, and hydropower (Viviroli et al 2007). Mountain systems supply cultural services, holding spiritual value to local inhabitants, and are recreation and ecotourism attractions (Price et al 1997).…”

The hydrological significance of mountains: a regional case study, the Ebro River basin, northeast Iberian Peninsula

“…In humid climates with a tropical influence, the average value of the coefficient even fell below 1.0. In a worldwide study, Viviroli et al (2007) found that the hydrological and ecological significance of the world's mountain regions could be classified as being of essential (23% of the world's mountain area), supportive (30%), occasional (28%) or limited (19%) importance.…”

“…is equal to, or greater than, 1000 m. In a global-scale study by Viviroli et al (2007), all areas over 1000 m a.m.s.l. were included as mountain regions, as were those between 200 and 1000 m whose relief roughness exceeded 20‰.…”