water is The city planner’s nemesis. Since the built environment is very impermeable, thanks to all the asphalt, concrete, and bricks, liquids accumulate instead of seeping into the ground. That’s what caused weeks of extreme flooding in California, which has so far killed 19 people and caused an estimated $30 billion in damage.
Engineers have traditionally viewed stormwater as a nuisance, building complex infrastructure like gutters and canals to funnel floodwater into rivers or oceans before they have a chance to form puddles. But in California and elsewhere, climate change is forcing a shift in that strategy. As the world warms, more water evaporates from the land into the atmosphere, and the atmosphere itself can hold more water as temperatures rise. Storms in the Golden State come less often, but when they do come they dump more water faster. The storm drain system cannot remove the water fast enough.
To prepare for this soggy future, engineers are turning to more natural flood protection plans that force water to seep into natural aquifers underground. Such a plan would simultaneously mitigate flooding and help the western U.S. store more water despite a runaway climate. “We need to think more creatively: How do we best use these giant subterranean sponges that can be used to supply drinking water?” says Katherine Kao Cushing, who studies sustainable water resource management at San Jose State University.
California’s water system is built for the squirrel-like Mediterranean climate. Fall and winter rainfall fills the reservoir system, supplying the state with water throughout the dry summer months. But the system can become strained during droughts like the one now ravaging the state: The past three years have been the driest since 1896. (Droughts can actually exacerbate flooding, since dry land won’t absorb water either.) Before this series of storms hit, some reservoirs in California were nearly dry. The storage capacity of reservoirs across the state is now close to the historical average. Such is the epic of this rain.
Snow cover is also important. It grows at high altitudes all winter, then melts and feeds reservoirs as temperatures rise. But climate models predict that most of the state’s snowpack will be gone by 2100, said Andrew Fisher, director of the University of California Santa Cruz Recharge Program, which studies groundwater resources. “Some models say it all,” Fisher added. “Let it sink in for a second. That’s more water than is behind all the dams in the state. It’s very sobering because we can’t possibly double the number of dams.”
To keep water for its people and its agriculture, California is ramping up water conservation efforts like installing more low flow toilets in homes and paying people to tear down their lawns for all sorts of stupid reasons other than thirst . It recycles wastewater from homes and businesses into ultrapure water that you can actually drink. But most importantly, it seeks to retain sporadic rainwater rather than drain it, building infrastructure to create “sponge cities”. These are popping up around the world; the concept has been widely used in China, and city planners in places like Berlin, Germany, and Auckland, New Zealand, are using it to deal with heavy rainfall.
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