Guess what? The past is no longer a reliable base on which to plan the future of water management. So says a prominent group of hydrologists and climatologists writing in Science. The group calls for fundamental changes to the science behind water planning and policy.
Managers currently operate on the premise that historical patterns can be counted on to continue. But human-induced changes to Earth’s climate are shifting the averages and extremes for rainfall, snowfall, evaporation, and stream flows. These are crucial factors in planning for floods or droughts, in choosing the size of water reservoirs, and in deciding how much water to allocate for residential, industrial and agricultural uses. Even with an aggressive reduction in greenhouse gas emissions, warming will persist and global water patterns will continue to show never-before-seen behavior.
“Our best current estimates are that water availability will increase substantially in northern Eurasia, Alaska, Canada and some tropical regions, and decrease substantially in southern Europe, the Middle East, southern Africa and southwestern North America,” said lead author Christopher Milly, a research hydrologist with the U.S. Geological Survey. Drying regions will likely also experience more frequent droughts.
“For agencies like the Army Corps of Engineers and the Bureau of Reclamation, this would mean fundamental changes in the way they do business. If you look at plans by those agencies for management of the Columbia River, essentially they’ve ignored climate change. For instance, until quite recently, the National Marine Fisheries Service didn’t even mention what climate change might mean for rehabilitation of fish runs.”
The authors propose a planning framework like the Harvard Water Program from the late 1950s and early 1960s, when scientists and engineers hammered out the basis for current water-management policies. A renewed effort in the spirit of the earlier program needs to incorporate shifting averages and variability.