For anyone who has ever flown into Las Vegas or Phoenix and taken note of the dusty landscape that surrounds these cities-in-the desert, it comes as little surprise to hear that they face major long-term water stress. But when an unprecedented drought brought normally lush, wet Atlanta to the brink of water catastrophe a few years ago, it was a different story.
Now a new report by the Columbia Water Center, produced in conjunction with Veolia Water and Growing Blue, could help expose the real nature of water risk in urban and rural areas throughout the country–even in places that most people think of as having plenty of water.
According to Water Center Director Upmanu Lall, most water stress tools developed to date base their analyses on average water supply and demand, usually within a given river basin. Typically, these analyses use estimates of groundwater recharge and river flow as measures of supply, forgetting, says Lall, “that the local river flow is coming from somewhere else.”
By contrast, the new Columbia Water Center analysis looks at average county-by-county precipitation to provide what Lall calls “a much more direct measure” of local renewable water supply and demand.
For many parts of the country, the study’s results are alarming, although perhaps not surprising. As seen in a Veolia Water infographic drawn from the report, huge swaths of the Midwest and much of California are in the “highest risk” category for water shortages. The most water stressed regions in the country, says Lall, are “dominated by deficits due to agriculture.”
Both nationally and globally, a large majority of water consumed is used for irrigation, and in the United States the vast majority of food crops are produced in those same water-stressed regions. These regions rely heavily on non-renewable groundwater to meet meet water needs.
But there are also surprises. The Washington, D.C., and New York metropolitan regions came out as having the highest “Normalized Deficit Cumulated (NDC)” for major cities, according to the study. The NDC was computed by taking 60 years of historical climate data and determining the largest deficit between renewable water supply and demand over a multi-year drought.
By using county data and restricting the definition of available supply to precipitation in the unit area measured, the study “effectively exposes” the degree to which places like New York and Washington must rely on huge water transfers from other locations to function, says Lall. These transfers set the stage for potential future conflicts over resources.
In Atlanta, the city’s dependence on far-flung water resources has already led to inter-state and sector disputes, with Atlanta attempting to secure enough water to continue its rapid urban growth, while Alabama and Florida fight to keep water flowing to sustain the environment, fishing industries and power generation.
In New York, the metro area’s enormous reliance on upstate water resources essentially puts an upper limit on regional agricultural and other development. In suburban Rockland County, for example, the local water utility is now proposing to build a controversial desalination plant to supply the county’s growing thirst. While desalination works, it is a highly energy-intensive and ecologically risky approach that’s typically associated with extremely dry countries like Israel and Saudi Arabia–places, in other words, that have few alternatives.
“Most people think the Eastern U.S. doesn’t have a problem,” says Lall. “But if you look at New York county, there’s no way it could meet its own water needs. Essentially, it has outsourced its water supply.” That may work fine during times of normal precipitation. But then a drought happens. “It’s only at these times that people realize they’re living on borrowed water.”