Earlier this month, the future fell upon Los Angeles. A long band of moisture in the sky, known as an atmospheric river, dumped 9 inches of rain on the city over three days. That's more than half of the amount the city typically receives in a year. This is the type of extreme rainfall that will become more extreme as the planet warms.
But the city's water managers were ready and waiting. Like other urban areas around the world, Los Angeles has been transforming into a “sponge city” in recent years, replacing impermeable surfaces like concrete with permeable surfaces like soil and plants. “Diffusion fields” were also constructed where water could accumulate and seep into the ground.
Between February 4 and 7, the metropolis secured 8.6 billion gallons of rainwater, thanks to traditional dams and all new spongy infrastructure. This is enough to supply water to 106,000 households for one year. In total during the rainy season, LA accumulated her 14.7 billion gallons.
Los Angeles, which has long relied on snowmelt and river water piped in from far away, aims to produce as much water as possible locally. “We're going to see a lot more rain, a lot less snow, and that's going to change the way we pump snowmelt and tap water,” said Art Castro, watershed management manager for the Los Angeles Department of Water and Power. “Dams and expansions are workhorses that harvest regional rainwater for flood prevention or water supply.”
Centuries of urban planning dogma calls for draining rainwater from large cities as quickly as possible using gutters, sewers, and other infrastructure to prevent flooding. But that clearly doesn't work anymore, given the increasingly catastrophic urban flooding that occurs around the world, so planners are now trying to capture rainwater and turn it into a debt rather than a liability. I'm trying to find smart ways to treat it as an asset. “Urban hydrology problems are caused by thousands of tiny ditches,” says Michael Kipersky, director of the Wheeler Water Institute at the University of California, Berkeley. “A driveway or a roof on its own doesn't cause a huge change in the water cycle. But when you combine millions of them into one area, it does. Maybe 1,000 Band-Aids can do that. The problem can be solved.”
Or in this case, a sponge. The secret to increasing a city's absorption capacity is by creating more gardens and other green spaces that allow water to percolate into underlying aquifers (porous underground materials that can hold water), so that cities can use that water when needed. It is to pump from. Engineers are also greening medians and roadside areas to absorb water that would normally flow from roads into sewers and eventually into the ocean.
As the American West and other regions grow increasingly dry, they are finding ways to produce more water themselves rather than importing it via aqueducts. (Incidentally, this strategy involves recycling toilet water into potable water so that cities use less water in the first place.) At the same time, counterintuitively, climate change is making storms more It's intensifying. For every degree Celsius of warming, the atmosphere can hold 6 to 7 percent more water, which means storms often have more water available to release as rain. In fact, research shows that atmospheric rivers on the West Coast, like the one that just hit LA, are getting wetter.
