Moreover, capital cost projections for desalination plants often greatly understate these facilities’ true cost. For example, the final cost ($1 billion) to build the ocean desalination plant in Carlsbad, California, which opened in late 2015, was four times higher than the original projection.

Our center has also explored whether piping in desalinated ocean water is a viable option for small, typically rural areas with public water systems or private wells that have run dry or are close to giving out. In diverse parts of California where this has happened, such as Porterville in the Central Valley and Montecito along the coast, the state is paying over $1 per gallon to truck in small supplies of bottled and vended water. That’s much higher than even the most expensive desalinated seawater.

In these cases, we have found that the relative economics and even the environmental impact may pencil out, but the politics and management of new pipelines do not. This is because water supply is typically governed locally, and many local areas beyond those benefiting would need to agree to a new pipeline from the coast.

More broadly, we find that proponents of these projects do not proactively pursue strategies that would make water access more equitable, such as designing utility rate structures that shield low-income households from higher costs, providing financial aid to small communities or consolidating water systems.

In most places, several other supply options can and should be pursued in tandem before ocean desalination. All of these steps will provide more water at a lower cost.

The first and relatively cheapest way to address water shortages is by using less. Finding ways to get people to use less water could reduce existing demand by 30%-50% in many urban areas that have already begun conservation efforts.

Second, recycling or reusing treated wastewater is often less expensive than desalination. Technology and regulations in this area are advancing, and this is already making large investments in recycling possible in many arid regions.

Third, storage capacity for enhanced capture of stormwater – even in areas where it rains infrequently – can be doubled or quadrupled in regions like Los Angeles and parts of Australia, at one-third to one-half of the cost per unit of desalinated water.

Even cleaning up polluted local groundwater supplies and purchasing water from nearby agricultural users, although these are costly and politically difficult strategies, may be prudent to consider before ocean desalination.

The feasibility of desalination as a local supply option will hopefully change by midcentury as water scarcity problems mount because of climate change. For the medium term, however, ocean desalination is still likely to play a small role if it figures at all in holistic water strategies for coastal urban areas.

This article is republished from The Conversation, an independent nonprofit news site dedicated to sharing ideas from academic experts. It was written by: Gregory Pierce, University of California, Los Angeles. The Conversation has a variety of fascinating free newsletters.

Read more:
California’s water supplies are in trouble as climate change worsens natural dry spells, especially in the Sierra Nevada

As Colorado River Basin states confront water shortages, it’s time to focus on reducing demand

Gregory Pierce received funding from the Resources Legacy Fund for one of the reports cited in this piece.