Urbanization is a global process that has taken billions of people from the rural countryside to concentrated urban centers, adding pressure to existing water resources. Many cities are specifically reliant on renewable freshwater regularly refilled by precipitation, rather than fossil groundwater or desalination. A precipitationshed can be considered the “watershed of the sky” and identifies the origin of precipitation falling in a given region. In this paper, we use this concept to determine the sources of precipitation that supply renewable water in the watersheds of the largest cities of the world. We quantify the sources of precipitation for 29 megacities and analyze their differences between dry and wet years. Our results reveal that 19 of 29 megacities depend for more than a third of their water supply on evaporation from land. We also show that for many of the megacities, the terrestrial dependence is higher in dry years. This high dependence on terrestrial evaporation for their precipitation exposes these cities to potential land-use change that could reduce the evaporation that generates precipitation. Combining indicators of water stress, moisture recycling exposure, economic capacity, vegetation-regulated evaporation, land-use change, and dry-season moisture recycling sensitivity reveals four highly vulnerable megacities (Karachi, Shanghai, Wuhan, and Chongqing). A further six megacities were found to have medium vulnerability with regard to their water supply. We conclude that understanding how upwind landscapes affect downwind municipal water resources could be a key component for understanding the complexity of urban water security.
General news | 2018-03-19
In 2017, we surpassed one thousand published articles in peer-reviewed journals and we hosted the fourth international conference on resilience and sustainability science. Another year to be proud of, we think
Research news | 2018-03-14
Amid an increase in megacities, changes in ecosystems far away can affect local access to freshwater
Research news | 2018-03-12
Ten essentials for guiding action-oriented research on energy transformation and climate change
Research news | 2018-03-09
To celebrate International Women’s Day, we have been highlighting some of our women researchers at the centre. In our final profile this week, we showcase associate professor Beatrice Crona, whose work spans from small-scale fisheries governance to global drivers of change.
Research news | 2018-03-08
To celebrate International Women’s Day, we are highlighting some of our women researchers. We would now like to showcase Jennifer Hinton, a PhD candidate studying the social dynamics of a sustainable biophysical resource economy
Research news | 2018-03-08
New method to map livelihood benefits of ecosystem services for guiding future land use decisions in the Sahel