Here’s how high-tech flights can help combat the dangers of seawater on the coast

CAPITOLA, Calif. (KGO) — Thousands of visitors throng the beaches of the Capitola-Santa Cruz area, unaware that they are on the front lines of an ongoing battle fueled by California’s drought. the enemy? Seawater is pumped into the same wells that provide clean drinking water to the surrounding communities.

“And the physics of it is, basically, if we’re pulling in seawater, how do we put a little bit of, or a barrier, a hydraulic resistance circuit to push back,” said Ron Duncan, general manager of Soquel Creek Water.

He explains that when the water table is low enough, wells near the coast can begin to draw in salty seawater. To combat that, the agency is expanding the practice of injecting treated wastewater into the ground. The goal is to recharge the groundwater and bring back the seawater.

We have seven miles of beach to roam. And what we’re going to do is extract water from our exploration, some of it to create a hydraulic barrier, but some of it as a water source,” Duncan explains.

But to achieve that delicate balance, the agency had to map out where the saltwater would come from. That requires looking deep beneath the waves and shore, with technology we’ve shown you here at ABC7. It’s known as an airborne electromagnetic survey, and it looks like something like a spaceship suspended from a helicopter. Grains penetrate the ground, drawing the geological map below.

Video: A spacecraft-sized inspection system could help determine where CA’s future water supply will be stored

Earlier this year, we profiled teams from Stanford and the California Department of Water Resources as they mapped geology in California. Future groundwater recharge programs are identifying areas where water flows easily into the aquifer. But Duncan said using AEM to find salt water on the coast was a different challenge. To do this, Sokel has partnered with a Danish company that has a version of the technology.

“And they flew the helicopter all day. Then they came back and landed, downloaded the data. And within 30 minutes we were able to see it 600 feet down to the ocean beach,” he says.

Combining data from the flights with other sources allowed the team to map the extent of saltwater encroachment along the coast and prioritize groundwater recharge programs.

It’s a strategy that could soon go up and down the coast.

“Yes, I think so. I think we’re just getting started on how to use the data,” said Kathryn Dulubak, Ph.D., who manages the electromagnetic survey program for the California Department of Water Resources.

Video: How CA’s Ancient Subterranean Waterways Are Key to Replenishing Depleted Groundwater

His team completed a new coastal survey last month, generating data that will be shared with water agencies.

“To answer the questions we think we’re going to be. So, where are good charging points, where can we get into the seawater?” She explains.

Drawing largely invisible battle lines, which help ensure already strained water supplies, drought and climate change pressures continue to build on our coasts.

“It doesn’t take a rocket scientist to see what could happen if we don’t act now,” said Duncan of the Soquel Creek Water District.

While coastal seawater intrusion is a widespread issue along the coast, rising sea levels are also creating new problems for inland watersheds in the Bay Area, experts say.

If you are on the ABC7 News app, click here to watch live