By mid-century, according to Tim Bardsley from the University of Colorado at Boulder, some of the streams that feed the city will dry up several weeks earlier each summer and autumn. Climate scientists have predicted that the American Southwest could become steadily more arid as the planet warms through a build-up of carbon dioxide in the atmosphere. But city planners need more than general warnings: they need a clear idea of what might happen in this or that environment.
“Because our research team included hydrologists, climate scientists and water utility experts, we could dig into the issues that mattered most to the operators responsible for making sure clean water flows through taps and sprinklers without interruption,” said Bardsley.
The researchers confirmed that every increase of 1°F meant, on average, a 3.8% decrease in annual water flow from the city’s watersheds. The lower the altitude of a stream, the more sensitive it was to increasing temperatures, which means that planners have to store more water, or rely on streams from higher altitudes.