Recent storms are filling up LA area reservoirs, but not just with water

By Nihar Patel

Pyramid Lake is a reservoir near Castaic, in Los Padres National Forest, California. Photo by Shutterstock.

After the recent storms, LA reservoirs in the San Gabriel Mountains are filling up, but not just with water — millions of cubic feet of mud and wilderness debris, too. The roughly century-old water infrastructure system was designed to handle a large influx of stormwater and other unwanted additions, but climate change is forcing LA County to adapt.

“We have seen an accelerated deposition of sediment and debris into a number of these reservoirs,” says Mark Pestrella, director of LA County’s Department of Public Works. “We've seen the need to clean these reservoirs up at a more frequent pace.”

As global temperatures increase, and droughts, fires, and heavy storms become more frequent and intense, Public Works has had to change its models for how the system is supposed to work. More frequent clean-ups, which prevent clogging of the valves regulating the water flow, mean more resources are needed.

“What that means is more money, more often contracting to do it,” says Pestrella. “The good news is the advanced planning has been done … and we believe we can continue to maintain it.”

The risks of not cleaning up the reservoirs are immense, especially to those living directly down the mountain in cities like Arcadia, Sierra Madre, Pacoima, Sunland, and Sun Valley. Pestrella says there is no current risk to those communities.

“We don't expect any of the dams … to break or to overflow due to any predictable or … future … rainfall,” Pestrella asserts. 

Pestrella credits the robustness of the system to investments funded by utility charges. He hopes increased spending will assist with the other vital function of the reservoir system: capturing and controlling water for millions of LA County residents to use. He recently helped lead Vice President Kamala Harris on a tour of a stormwater capture facility in Tujunga, one of more than two dozen in the County. 

“I was really surprised, really delighted to see that the [Biden] administration understood the importance of these reservoirs, and actually … committed to helping us out with designating them … as a very important part of the system that protects people from the effects of climate.”

Pestrella is encouraged by the amount of water captured after the recent storms. He says it’s enough to supply more than a million people for one year. But with more hot, dry years looming, even Pestrella acknowledges it’s just a drop in the bucket for what may be needed.

“It's just a down payment on that drought that we've been experiencing… we got to keep investing in this system.”