As the drought grinds on, water managers in Southern California are trying to make the region less dependent on water piped in from elsewhere: They’re focusing on local sources, especially those underground. But ongoing challenges make exploiting groundwater more difficult than just digging a well.
Among the challenges:
- The intrusion of salt water into underground aquifers
- Pollution from industrial sources and underground gasoline tanks
- Tapping aquifers that don't naturally replenish themselves
Southern California has drawn on water supplies contained in the ground for a century.
You can see evidence of this in Seal Beach’s Leisure World, an unlikely place to find a geologist. Past the manicured lawns and sidewalks full of retirees on scooters, U.S. Geological Survey hydrogeologist Michael Land stands over a well in a parking lot. The well is a window into seven layers of aquifer below.
“One of the reasons why we drill these holes in the ground is to figure out you know, OK, what the heck is going on here through geological time,” he says.
Land is here to pull water quality samples. He studies the central and west L.A. basin – the geology that holds water in place 50 to hundreds and even thousands of feet below the surface. These are aquifers. To understand them, Land says to picture a bathtub.
“And the bathtub is filled with all sorts of materials. Sands, gravels, silts and clays. In this basin it tends to be a lot of silt and sands.”
Working with the Water Replenishment District of Southern California, the USGS has mapped the L.A. basin bathtub pretty well. In fact, in the coastal region, and in the California desert, there are scores of these underground water deposits that can yield, by some estimates, enough water a day for 3 million households. But even where those supplies are known, plenty of obstacles make that water hard to reach.
In low-lying areas like Seal Beach, the challenge is salt water intrusion. In the first half of the Twentieth Century, too much pumping in the L.A. basin pulled salt water into the aquifers. It’s a potential problem to this day.
“We were pumping before we knew what we were doing, and that was precisely why in the '20s and '30s the ocean came rolling in,” Land says.
Over the years since, the water replenishment district has injected water into almost 300 buffer wells to form a barrier between the ocean and the aquifers from which Southern California takes water.
Salt water’s not the only problem. In the San Gabriel and San Fernando valleys, industrial chemicals like volatile organic compounds have fouled groundwater. Some aquifers are designated Superfund cleanup sites where the rocket industry once boomed.
Marty Adams is the director of water operations for the Los Angeles Department of Water and Power. He says some pollution’s just from old tanks under gas stations.
“So we’re dealing with pollution from the past,” Adams says. “And it’s taken decades for that pollution to get forced down through hundreds of feet of soil into where it’s in the groundwater aquifer.”
Contamination has forced the DWP to take more than half of its groundwater wells out of service. Now L.A. is wrapping up a multiyear groundwater status report with the goal of creating an inventory for pollution and contaminants that compromise San Fernando Valley groundwater.
The goal is to know what’s there, so DWP can figure out how to remove it. Adams estimates it’ll cost $600 million to $900 million to build a state of the art treatment plant.
“That’s one of the reasons we’re looking for any assistance from the state in terms of a water bond, assistance from the federal government, certainly assistance from the folks who polluted. It’s a really big ticket item,” Adams says. “We have to reclaim our local water source, and this is the only way to do it.”
Water managers are making these choices as disruptions to longstanding climate patterns are changing precipitation — and the speed at which aquifers recharge.
The desert town of Joshua Tree has been pumping water from the ground for 50 years. When pumping started, the Joshua Basin Water District had inaccurate information that soon became outdated.
“In essence, we are mining our basin," says Susan Greer, the water district's assistant general manager. "We are taking out water that cannot and will not be naturally replaced.”
In 1990, high desert communities including Joshua Tree voted in a special tax to build a pipeline to the California Aqueduct 70 miles away in Hesperia. Greer says the tax shows up in higher water rates and property assessments.
The pipeline will bring water from the California Aqueduct into ponding areas where it’s meant to fill aquifers.
A straw is only good if there’s water to suck through it. This year, because of the drought, the managers of the State Water Project have promised water contractors about 5 percent of what they’ve requested.
Greer hopes it’s an aberration. She points out on average the state has delivered about 65 percent of allocation requests.
“I think that’s a pretty good indicator of what’s going to happen in the future. And there may be a blip, but we are confident that we are going to overcome that and be back in business again receiving water from the state,” Greer says. “Too much of the state relies on that supply. The state won’t let us down.”
Given the predictions climate scientists make about more and more frequent droughts, the state likely will have to work hard to keep that water flowing.