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  • California's current drought has highlighted the need for improved freshwater management and has elevated seawater desalination in discussion of water supply alternatives.
  • Seawater desalination is energy-intensive and very expensive, and can have significant impacts on the marine environment through the intake of large volumes of seawater containing marine life, as well as from the discharge of brine.
  • In the vast majority of locations, water conservation, water use efficiency, stormwater capture, rainwater harvesting, and wastewater recycling measures are less expensive, have fewer negative environmental impacts, and have multiple economic and environmental benefits over seawater desalination.

For California, 2013 was the driest calendar year ever recorded across virtually the entire state. On January 17, 2014, Governor Jerry Brown proclaimed the drought to be a State of Emergency, directed state officials to take all necessary actions to assist the hardest hit communities, and called for all Californians to pitch in to reduce water use by 20 percent. In short order, lawmakers and the governor enacted a relief package that provides $687 million in drought relief to fund projects to improve conservation, clean up contaminated groundwater, make irrigation more efficient, and help those hurt most by the drought.

This bi-partisan, emergency action provides critical support for drought relief alternatives that are the most cost effective, readily available, and beneficial to the environment and communities' quality of life. While the agencies and experts have clearly identified those actions best suited to provide relief, some observers wonder whether the long-term answer to California's drought lies in the ocean through the promotion of seawater desalination.

What is Seawater Desalination?

Desalination entails removing salt and other minerals from seawater, brackish water, wastewater, or contaminated groundwater to create pure water for drinking and other purposes. With 3,427 miles of tidal shoreline and 74 percent of the California population living in coastal counties, it is reasonable to consider that seawater desalination might play a role in the state's water supply portfolio. There are a range of different desalination technologies, though most modern plants use either distillation or reverse osmosis in which high volumes of saline water pass through membranes to remove salts from water.

This issue brief -- prepared by the Natural Resources Defense Council, California Coastkeeper Alliance, Surfrider Foundation, Heal the Bay, Orange County Coastkeeper, and California Coastal Protection Network, Residents for Responsible Desalination, Southern California Watershed Alliance, and the Desal Response Group -- offers an overview of the science and policy related to seawater desalination and demonstrates why this option is generally the least promising option for drought relief. Other water supply options should be prioritized over seawater desalination because:

  • Seawater desalination is very expensive, costing on average four to eight times more than other options;
  • Seawater desalination is typically the most energy-intensive water supply option, resulting in significant greenhouse gas (GHG) emissions;
  • Multiple large seawater desalination projects are likely to have significant negative impacts to the valuable marine resources that California has invested millions of dollars to protect; and
  • Experience demonstrates that large, expensive desalination facilities and associated infrastructure can take many years to build and bring online, yet the water demand and price may be insufficient to justify continued operation of the desalination plant when less expensive water supply and demand management alternatives are available: this creates significant financial risk for ratepayers and taxpayers.


In preparing this paper, the signatory organizations have comprehensively reviewed California's water supply options and have determined that seawater desalination should only be pursued with caution and only after conservation, stormwater capture through the use of "green infrastructure," water use efficiency, and wastewater recycling have all been fully implemented. These preferred alternatives are not only less expensive, they prevent pollution, contribute to habitat restoration, and reduce energy usage.

If and when seawater desalination is appropriate, projects should be carefully scaled to meet demonstrated water supply needs. Then, projects should be designed and sited and the best technology available should be used to:

  • minimize the intake and mortality of marine life;
  • minimize adverse impacts to the marine environment from the facility's waste discharge;
  • and avoid conflict with ecosystem-based management activities, especially ongoing implementation of the Marine Life Protection Act, and climate change and disaster preparedness.

last revised 5/21/2014

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