Wondmagegn Yigzaw & Faisal Hossain

It’s no surprise that as cities grow larger, their water supplies experience more demand. But how exactly to translate this knowledge into action steps has, until now, escaped many research studies. A new study, which analyzed river basins in 42 major cities throughout the United States, has determined not only which ones may experience water shortages in the future, but also includes policy recommendations.

Led by associate professor Faisal Hossain, the study was conducted by Wondmagegn Yigzaw, an alumnus of Tennessee Tech University where Hossain taught prior to joining UW. The paper was published in the American Geophysical Union Journal Earth’s Future in December 2016.

"We tried to answer the question ‘so what?’ and bridge the gap between researchers, policy makers and the general public,” Yigzaw said. “We were able to identify potential solutions to cities where future and present water availability is in question.”

Unlike some water sustainability studies, the researchers took a bottom-up approach by considering additional factors in each city that impact water demand and availability, such as population growth, migration, water use efficiency and local water availability patterns related to landscape.

Total population of selected cities (a) and population growth rate between 2010 and 2013 (b).

“This study makes the future assessment more robust as it is not relying on just climate change scenarios, but also local factors that dictate local conditions in a more pronounced manner,” Hossain said.

While the research findings do include some good news, primarily that many growing cities have reduced their water consumption, the researchers nevertheless found that a decrease in surface water run-off will likely impact the available water supply. Making the situation more concerning is that the growing metropolitan areas tend to be located in warm climate zones that receive little rain.

In particular, the study recommends considering desalination for West Coast Cities such as Los Angeles, Calif. and San Diego, Calif. as the Colorado River’s water supply has been drastically reduced in recent years. The Colorado River, which is one of the primary rivers in the Southwestern United States, provides water for seven states. Desalination, although more expensive than existing freshwater treatment processes, has the potential to transform sea water into drinking water for populations living near the coast. The study also found that most cities within the Mississippi River basin are unlikely to face water shortages given relatively resilient water availability to future climate change. This has led the researchers to recommend transferring water from Mississippi to cities such as Phoenix, Ariz., Tucson, Ariz., and the Central Valley, Calif., where desalination is not feasible.

The study was based on terra-byte scale datasets from satellite remote sensing and climate models spanning several decades and was funded by a NASA Earth and Space Science Fellowship awarded to Yigzaw.