Could the ocean slake California’s thirst?

“Water, water, every where, And all the boards did shrink; Water, water, every where, Nor any drop to drink.”

Poet Samuel Taylor Coleridge penned those words in his 1798 poem, “The Rime of the Ancient Mariner,” to describe the plight of becalmed sailors who could die of thirst while surrounded by limitless expanses of undrinkable seawater.

In a way, it also describes California’s plight. Despite its 3,427 miles of Pacific Ocean coastline, including bays, inlets and tidal marshes, the state has an ever-widening gap between its demand for water and its supply.

Naturally, there has been a decades-long debate over whether the state should tap into that endless supply of seawater to bridge the gap, emulating other arid and semi-arid societies, particularly in Australia and the Mideast.

From a technical standpoint, it’s a no-brainer. Desalination plants, including a few already operating in California, do exactly what they are supposed to do — strip the salt from seawater, converting it into freshwater suitable for drinking or any other purpose. The barriers to building dozens of desalination plants along the coast are economic, environmental and political.

Such plants require oodles of electrical power to pump in the seawater, push it through filters that remove the salt and then return the uber-salty brine waste either to the sea or into another process.

A massive desal program would place a new burden on a power grid that already struggles to keep up with demand on very hot days as it evolves from natural gas-fired power plants to renewable sources such as wind and solar. Desal’s power demand also contributes heavily to the bottom line costs of producing water, making it more expensive, at least so far, than water from other sources.

Finallly, environmental groups have generally opposed desal projects on assertions that pumping seawater into the plants and returning brine to the sea run the risk of damaging delicate marine ecosystems. But the groups have another, unspoken reason for opposition. Restricted water supplies have been used as a tool to oppose new residential development and increasing water supply undercuts that political tool.

In combination, all of those points were cited in the California Coastal Commission’s rejection of a much-debated desal project at Huntington Beach in Orange County earlier this year. The plant would have been a near-clone of a desal facility in Carlsbad, further south along the coast.

At the time, it appeared to be a death knell for the expansion of desalination in California — something that Gov. Gavin Newsom’s administration envisions in its overall plan for closing the demand/supply gap as climate change and semi-perpetual drought diminish traditional supplies from winter rains and snowfall.

However, last month the Coastal Commission approved another Orange County desal project, one that would use somewhat different technology to pump in seawater and dilute the leftover brine before returning it to the sea.

Environmental groups gave their blessing to the Dana Point project, which made a big difference in the Coastal Commission’s attitude, as is the fact that it’s only one-tenth the size of the Huntington Beach project and would serve purely local customers of the South Coast Water District.

The approval was an indication that desalination could, as the state’s water plan envisions, play a significant role in California’s water future, which will be much different than its abundant past.

That said, desal probably wouldn’t be the silver bullet of limitless supply that some have hoped it would be. It would be more of a reliability factor, something that Californians could depend on working when traditional supplies fall short.