Displacement of the salt line

Salt in drinking water supplies will become more common in cities, especially on coasts, said Allison Lassiter, assistant professor of urban planning at the University of Pennsylvania.

“Most cities that were historically in places that weren’t going to experience salt water, that’s starting to change,” Lassiter said. “The salt line is already moving inland.”

Imagine the ocean shore, but underground there is a line where fresh water and sea water meet, called the salt line.

This line of salt moves with the tides. But rising sea levels and more people living near the shore drawing on fresh water underground can also draw more salt water from the ocean to land.

She said places across the United States and around the world are now beginning to study this issue. It’s such a big deal in Jakarta, Indonesia that it’s part of an ongoing conversation to move the entire capital.

“No” to desalination

Cape May has solved its problem with desalination. Could the rest of the world follow suit?

Former Cape May Mayor Ed Mahaney thinks there’s a lot of potential.

“[In] 1995, desalination would have been the last alternative because of its lack of notoriety among the general public and government authorities, and also because of its cost. Today, I think he has a huge upside.

The same goes for Joaquin Esquivel, chairman of the Water Resources Control Board in California.

“Removing these salts…is a very important strategy that California has used and will need to use more to…make every drop count here in a state that is increasingly obviously stressed by climate change and the aridification.”

California is going through drought conditions. Aridification refers to the climate becoming drier over the long term, not just in cycles of seasonal drought.

California recently considered a desalination plant in Huntington Beach, southeast of Los Angeles. The plant would have supplied 50 million gallons of fresh water from seawater. The governor weighed in to support the plant. But after a nine-hour meeting, the California Coastal Commission unanimously voted “no.”

So why would California deny a drought-tolerant water supply?

This brings us to some of the desalination issues.

The Huntington Beach plant proposal is not quite the same as the Cape May one.

First, the Huntington Beach plant would use seawater and not groundwater that is a little too salty. There is a lot more salt to filter out and the remaining water that needs to be dumped is much saltier than seawater. It would also come out so fast it would kill aquatic life, to which the California commissioners were are opposed.

Second, any type of desalination is expensive. It takes a lot of energy to run those big pumps to push the water through the filters. A widely cited 2019 report by researchers at the University of California, Los Angeles found that this Huntington Beach plant would make water much more expensive, something the commissioners couldn’t accept. The energy needed for desalination creates an additional problem if much of it comes from burning fossil fuels, which makes climate change worse.

Moreover, no local municipality had agreed to buy this water. Lassiter, the researcher who studies saltwater intrusion, said it might have been a problem later. She cited the case of Brockton, Massachusetts, which pushed in 2008 to build a desalination plant after a drought.

“After the contract was signed, they ran a conservation campaign and people were able to reduce their water use so much that they no longer needed the desalination plant and yet they were locked into a contract. costly afterwards,” she said. . “Desalination is usually the most expensive option compared to all other options, so it’s best to exhaust all other types of options.”

The future of desalination

One important alternative that Allison and various other researchers have said cities should try first is wastewater recycling — making better use of the water we currently discharge into sewers. Southern California is already a leader in this type of technology.

That’s not to say desalination isn’t part of the future.

Meagan Mauter, an associate professor of civil and environmental engineering at Stanford University, leads a research group that focuses on desalination. She points out that two other smaller desalination plants in California have not met the kind of resistance that the failing Huntington Beach plant has encountered, so voting against that plant is not a vote against desalination in his outfit.

“What I expect to see is a combination of things: I think we’re going to use desalination technologies that were originally designed for seawater desalination to desalinate a whole range of waters non-traditional.”

An example of non-traditional water desalination would be to treat groundwater that is too salty, as Cape May has done.

The technology behind desalination could also improve. Mauter said research is now focused on downsizing plants, pairing them with renewable energy, and finding better ways to get rid of the extra salt water that’s left behind.

Joaquin Esquivel, chairman of the Water Resources Control Board in California, said that with climate change, his state faces an unprecedented challenge when it comes to access to water.

At the same time, the potential for better technology makes him optimistic about the future. He recently attended the opening of a small desalination plant in Menifee, California, not far from Los Angeles.

“It’s exciting to see, because the needs…drought pressures, climate change are driving the innovation that’s going to fuel this next generation of projects in the state.”