Desalination could help California -- but only if it’s done right
Californians used to call it earthquake weather, the unseasonably warm, dry, blue-sky days that pushed deep into this year’s rainy season. Now we just call it drought. Unfortunately, the state’s water resources are at critically low levels (12% of normal Sierra Nevada snowpack for this time of year) and the crisis is unlikely to go away soon or for long.
A report by the U.S. Geological Survey predicts that with changing patterns of rain and snow we will see more frequent and intense droughts and flash flooding in California’s future. “As global warming proceeds, we’re going to experience combinations of environmental conditions unlike any we’ve seen in the past,” warns USGS scientist James Cloern, the study’s lead author.
According to the state’s Climate Change Center, even with moderate warming projections we could lose 70% to 80% of the Sierra snowpack (which represents one-third of the state’s water supply) by the end of the century. It is doubtful if water conservation, storage and reuse will be enough to meet the requirements of future generations, even if they might just meet the needs of today’s 38 million Californians.
As a result, large-scale desalination of seawater and brackish groundwater, which has long been debated, promoted and litigated up and down the coast, may soon emerge as an important part of our water supply portfolio. But this should only happen if it’s done right, so as not to harm the ocean’s health, which is as much a key to the state’s economy and way of life as its freshwater resources.
The licensing of desalination plants in California has been a haphazard process, led by local water districts and developers and engendering a lot of dead-end battles. Santa Cruz invested $15 million in “desal,” then put its plans on hold in the face of popular opposition that included genuine environmental concerns and generalized NOBO (Not on My Bay or Ocean) attitudes.
California has a few small desalination plants and proposals for more than a dozen large ones. The Boston-based Poseidon company is promoting two $900-million, 50-million-gallon-a-day projects for Huntington Beach and Carlsbad. But the company has also claimed that environmental safeguards called for by the state Coastal Commission are “a poison pill” that could kill the Huntington Beach project. Perhaps Poseidon would be more comfortable taking its business to Saudi Arabia or Texas, where desalination operates with little or no regulation.
Taking the salt out of seawater is nothing new. President Kennedy opened the first U.S. desalination plant in Texas in 1961. There are two basic models: vacuum distillation, which converts saltwater to water vapor and leaves the salt behind, and reverse osmosis, which filters seawater through a semipermeable membrane to achieve the same result.
Desalination is more costly than other water sources. But improvements in the technology, combined with drought, general water scarcity and growing water demand, are beginning to make it commercially competitive. Aside from cost, obstacles to desalination include high energy use and the risks associated with what’s pulled into the intake pipes and what’s pumped back out.
Both desalination processes are energy intensive , although reverse osmosis is more energy efficient. Critics argue that unless desalination is powered by clean, non-carbon energy sources, it will contribute mightily to the very process of global warming that is generating water loss and scarcity.
Desal plants also require intake pipes, which can result in large-scale trapping of millions of marine organisms. The plants can (and some do) bury intake pipes under sand or gravel, below the seafloor, to avoid the entrapment problem. This was the Coastal Commission’s recommendation for Huntington Beach that Poseidon rejected as a “poison pill.” That project is now on hold as the company regroups to “study” the problem.
Another desalination issue is the outflow. The process requires the discharge of salt brine concentrate, sometimes contaminated with anti-corrosion cleaning agents from the pipes. The salt brine, which is heavier than seawater, can sink to the ocean bottom and harm ocean life and habitat. Its negative effects can be diluted by mixing it with wastewater or using a series of shower-head-like bottom diffusers to disperse it. The State Water Resources Control Board is formalizing a set of rules to address these issues.
These problems may be mitigated simply by moving desal off the beach. The technology’s most practical application may be to convert brackish inland groundwater, where sea level rise and past groundwater pumping is leading to salt intrusion in the water table and aquifers. It could also be the key to reclaiming agricultural and other contaminated water, because the technology can separate out clean water from impurities other than sea salt. Of course, waste disposal will remain a challenge wherever the technology is applied, but clean, potable water is increasingly going to be worth the effort.
Can desal help save California from its water crisis? A lot depends on the ability of the state to arrive at a solid set of environmental standards for the use, siting and scaling of the technology in the next few years, as it says it will. The state water board plans to adopt technical use standards by the end of this year. State action will also bring clarity to the local licensing process.
At that point, desalination could become a sustainable addition to the innovative water use solutions California will have to develop if it’s to address the challenges represented by today’s drought and our rapidly changing climate.
David Helvarg is executive director of Blue Frontier, an ocean conservation group. His latest book is “The Golden Shore: California’s Love Affair With the Sea.”
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