Researchers map all US interbasin water transfers

A comprehensive map of all interbasin transfers (IBT) in the US has been created by researchers from the department of Civil and Environmental Engineering at Carnegie Mellon University (CMU).

IBTs are man-made transfers of water between naturally occurring watershed basins that are used to distributed water resources based on supply and demand, according to a statement from the CMU College of Engineering.

This network of pipelines and waterways connects watershed basins across the US, meaning cities can get an adequate water supply. New York City imports roughly 90% of its water from the Catskill and Delaware basins through IBTs, for example.

With more than 15% of the US population deemed to be “at risk” of water scarcity, these IBTs are becoming increasingly crucial for coping with evolving water demand. However, the network has never been mapped with the latest techniques.

CMU PHD student Kerim Dickson and Civil and Environmental Engineering department head David Dzombak set out to address this problem, and expand knowledge of the IBT network.

“This is the first inventory of IBTs occurring across the US that’s been done since 1985,” explained Dzombak. “And that one was done by mail survey. But we now have access to water resource databases, such as the US Geological Survey’s National Hydrography Dataset, that we have been able to use to compile a much more comprehensive survey than has ever been done before.”

According to the CMU statement, Dzombak and Dickson’s map reveals there is a lot more water being moved around the US than ‘many would expect.’ The study, which has been published in the Journal of the American Water Resources Association, shows that Florida, Southeast Texas, California and Arizona have the largest number of transfers across watershed basins.

Although climate change and population density can provide some explanation for the distribution of IBTs, the researchers argue that more research is needed to determine exactly why some regions are so reliant on water imported from elsewhere.

“Without IBTs, cities wouldn’t be sustainable in large sections of the country, such as the southwest,” Dzombak said. “Los Angeles, Phoenix—much of their water is brought in from the Colorado River. That’s a critical lifeline for the city of Phoenix. These two locations, along with much of the Southwestern US, are under pressure from climate change that is only going to get worse.

“This survey helps us understand where the IBTs are,” Dzombak continued, “which then gives us some ability to look ahead and gain insight. With this understanding, we can start to pose questions like: If the populations in Denver or Phoenix or Houston increase by X, how will that affect the city’s ability to acquire enough water? How will that change pressure for bringing water in from elsewhere? You can ask questions about what changes in population, agriculture, and economy will put on different parts of the country for IBT. The work we’re doing helps make these kinds of assessments possible.”