Researchers found that 19 of 29 large cities depend on evaporation from surrounding lands for more than one-third of their water supplies.
Urbanization has taken billions of people from the rural countryside to urban centers, adding pressure to existing water resources. Many cities rely on renewable freshwater regularly refilled by precipitation, rather than groundwater or desalinated water.
A study led by Colorado State University found that 19 of the 29 largest cities in the world depend on evaporation from surrounding lands for more than one-third of their water supplies. Researchers also found that the dependence on this water supply is higher in dry years. The findings have implications for land managers and policymakers who oversee urban water security.
CSU research scientist Pat Keys is part of a team that had previously coined the term “precipitationsheds,” a watershed of the sky that identifies the origin of precipitation falling in a given region. The new study, “Megacity precipitationsheds reveal tele-connected water security challenges,” is published in PLOS One.
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Image via Patrick W. Keys, Colorado State University