Solving L.A.’s Water Problems By Turning It Into A Giant Sponge

As California’s drought problems continue, every drop of water that hits the ground needs saving.


When rain falls in Los Angeles, most of it flows away–despite how desperately the city needs water. As the drought continues, and as climate change threatens future water supplies, some experts think the city needs to be fully redesigned to soak up stormwater block by block.


Right now, the city is set up to get water from formerly snow-filled mountains that are warming up.

“We’re not designed for rain in the west,” says Hadley Arnold, co-founder of the Arid Lands Institute, a nonprofit and research at Woodbury University that is working on tools to help redesign the area’s approach to water. “We capture snow, and dispose of rain. So in a changing hydrologic cycle where there’s less snow, rain has more value, and we need to figure out how we’re going to grab it.”

Scott Jezzard, Angelito Villanueva, Bianca Bouwer/Perkins+Will

Capturing more rain would solve another problem–the huge amounts of energy that are currently used to pump water to L.A. “We’re using a lot of gas and coal to deliver our water to Los Angeles–and places like San Diego, Phoenix, Denver, and Las Vegas–which only exacerbates the problem,” Arnold says. “We warm the atmosphere further by trying to get these diminished snow resources. So how do you uncouple water from energy? That’s a design question.”

Right now, stormwater flows down roofs, roads, and parking lots and into drains leading to the ocean or the concrete-covered L.A. River. The Arid Lands Institute envisions turning the city into a giant sponge instead, where each building and yard can collect rain in a decentralized network.

They’ve created a new tool to help designers figure out how to optimize every house, apartment building, and street for rain. “It takes data from a lot of other disciplines that architects wouldn’t have access to or necessarily an interest in, and gives us a kind of martial plan for the city,” Arnold says.

David Bradshaw, Laura Arreola/Perkins+Will

The tool maps out the city into zones. Some areas can collect water; others can store it above-ground, because of pollution issues; and a third zone is only suited to send water somewhere else. Even within a neighborhood, zones can change, and the tool can tell an architect or homeowner exactly what they should do.


“Your lot might have a particular function, and your next door neighbor might have a different system,” Arnold says. “You would know the design approaches for your particular building would be, and designers can innovate within them, so that every individual project is working for the greater good.”

The nonprofit is partnering with architects to create examples of how future L.A. buildings and infrastructure might grab, store, recycle, and treat water. In a competition last fall, architects competed to design the “House of Retention,” a hypothetical 40,000-square-foot building near the L.A. River that would capture every drop of water that landed on the site.

Designers experimented with strategies like water towers, natural filtration systems, and hydroponic gardens built into facade walls. In future work, the nonprofit plans to explore new approaches to roofs, foundations, and walls that can store water instead of keeping it out. Sidewalks could be lined with bioswales to soak up more rainwater, and sidewalks and roads could be permeable, so water flows into the ground instead of into drains.

By some estimates, around 82% of the water used by City of L.A. could be supplied through conservation, recycling, and capturing stormwater, instead of pumping water hundreds of miles from somewhere else. In the L.A. River alone, rough estimates suggest that the stormwater that currently washes away could meet the needs of 2.5 million Angelenos.

Arnold is optimistic that the city will change–and as the historic drought continues, it may have to make that change soon. “It’s a perfect storm of progressive leadership and the school of hard knocks,” says Arnold. “I think we’re going to figure it out here, and then I think we can start to be a trading partner with other people in water stressed regions around the world.”

About the author

Adele Peters is a staff writer at Fast Company who focuses on solutions to some of the world's largest problems, from climate change to homelessness. Previously, she worked with GOOD, BioLite, and the Sustainable Products and Solutions program at UC Berkeley, and contributed to the second edition of the bestselling book "Worldchanging: A User's Guide for the 21st Century."