Los Angeles rethinks how to capture and store rainwater

As climate change brings stronger storms and longer dry spells, Los Angeles is rethinking how it handles water, working to slow it down, soak it in, and store it for the future.  

The city is using a so-called "sponge city" strategy that turns the rain into a local resource.

"Essentially a sponge is something that absorbs water, right, and then slowly releases it," said LADWP Project Manager Johanna Chang.

Flooding is becoming more challenging, even during short storms, because the weather is growing more intense and unpredictable. Chang points to the recent occurrence of atmospheric rivers.

"We work together with the LA County Flood Control District to optimize stormwater capture and recharge to not only help alleviate the flooding but also increase our local water supply," Chang said.

The Tujunga Spreading Grounds is one of the key components of LA's sponge city strategy. Instead of sending stormwater out to the ocean, basins slow its flow, allowing it to soak into the ground and recharge local groundwater.

Looking to the future, city officials are expanding these systems wherever they can.

"We are continuing to look at developing and expanding our portfolio of stormwater capture projects to prepare for climate change," Change said.

One problem LA faces is limited space, so the city is getting creative with its solutions.

"We've partnered with our City of LA Recreation and Parks and have developed stormwater capture projects at local city parks, building infiltration galleries for additional capture and recharge," Chang said.

Permeable pavement also plays a role, which works differently from traditional concrete. Chang says the newer concrete absorbs the water, allowing it to trickle down through the ground into the local aquifer. And the payoff can be significant.

"The last wet year, we were able to capture about 27,000 acre feet of water, which exceeds its design capacity," Chang said.

Beyond flood protection, sponge infrastructure improves water quality and strengthens communities hit hardest by flooding.

"We like to implement our projects in areas that have flooding issues, not only for recharging our groundwater basin but also helping with the local flooding issues," Chang said.

From spreading grounds to permeable streets, Los Angeles' sponge city vision is about preparing for a wetter—and drier—future, turning storms into protection, supply, and resilience.