By Fred Pearce
Dams are supposed to collect water from rivers and redistribute it to alleviate water shortages, right? Not so fast. It turns out that in most cases they actually create water scarcity, especially for people living downstream.
Almost a quarter of the global population experiences significant decreases in water availability through human interventions on rivers, says Ted Veldkamp at Vrije University in Amsterdam, the Netherlands. Those interventions primarily involve dams that take water for irrigation or cities, or to generate hydroelectricity.
Winners and losers
To investigate the impact of dams on communities, Veldkamp and her colleagues created a detailed modelling study that divided the world into 50-kilometre squares. They used this to assess water scarcity between 1971 and 2010, so they could identify the hydrological winners and losers from dam interventions.
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