Ocean Water Desalination Emerges as an ‘Option' for California's Water Agencies to Consider

What are the key issues raised by the use of desalinated water in California?

The technology for ocean and brackish-water desalination works. In fact, there are a number of different technologies in use around the world. So the question is not about technology. In California the principal technology being considered for desalination is reverse-osmosis (RO) in which water is driven through a membrane at high pressure to separate the salts from the potable water.

All of the different desalination technologies are expensive relative to water supplies that we are used to-surface diversions and groundwater extraction. But some of the existing so-called "conventional" systems are not without significant costs as well. Ocean desal, and certainly brackish-water desal, are becoming more competitive in the marketplace. The overarching point is that all water supplies have economic and environmental costs and tradeoffs. We're at a stage now of giving more serious consideration to these costs, both environmental and economic, for all water supplies. In my view, that's a helpful and healthy dialogue.

MWD General Manager Jeff Kightlinger told MIR several months ago, "California's water agencies need diversified toolboxes to meet the state's water needs . . . . desalination should play a small but significant part." What role should desal play in the state's toolbox?

I generally agree, and I would use the term "portfolio," which has a more specific meaning than toolbox in that there are attributes and value of different water supply options that range from reliability, to cost, to environmental impact. Desal would clearly be on the high end of cost, but as long as one can get the energy, the reliability is quite high.

I think MWD is pursuing the right path by keeping the door open to all water supply options and looking carefully at all the pros and cons. They have incentives for desal, and some have argued that efficiency, recharge, and wastewater reuse should receive at least comparable incentives.

I think that argument has merit. Those other sources shouldn't be disadvantaged, but that doesn't mean we shouldn't also look at ocean desal. MWD and some of its own member agencies, as well as water managers around other parts of California, are looking seriously at ocean desal for the same reason, adding it to their portfolio if indeed it pencils out and makes sense.

What role does energy use and energy cost play in considering desal plants in Southern California?

A lot of discussion has focused on energy because desalination processes are energy-intensive. On the order of 4,000 and 5,000 kilowatt-hours per acre-foot are required to desalinate and deliver ocean water. The figure is dropping a bit with improved membrane technology and improved pressure recovery in the systems. I've seen lower numbers from engineering analyses that look encouraging, but I've been using 4,400 kilowatt-hours per acre-foot as a placeholder figure for energy intensity.

By comparison, delivering water to the end of the east branch of the State Water Project in San Bernardino requires a little over 3,200 kilowatt-hours per acre-foot, which is pretty energy-intensive water. Some of the users on the state system at higher elevations actually receive water that exceeds the 4,400 kilowatt-hours per acre-foot figure. So some existing sources are roughly in the same range as ocean desal in terms of energy intensity. Other existing water supply sources are very low energy-intensity, and some are net positive as energy is generated from the water as it drops in elevation.

You're implying that the strongest argument for desal is that it ought to be part of a water portfolio, but not relied upon. Is that a fair statement?

I'd adjust it just slightly. I think that looking carefully at all water options makes good sense. Whether or not we should proceed with specific projects is another question. We need to analyze and understand every option-from building new dams to using water more efficiently to recharging groundwater to desalting brackish water to ocean desal. And we need to be honest about the economics and environmental impacts of all of these options and be able to compare them apples-to-apples.

The current dialogue around ocean desal has been very helpful in improving the level of analysis of all of these options. At the end of the day we have to choose a portfolio that involves a combination of costs and impacts. It'll be a political process, and it needs to be informed by solid science and rigorous economic analysis.

Let's turn to your academic work at UCSB. What projects and issues are you and your students engaged regarding water policy in Southern California?

The Water Policy Program at the Donald Bren Graduate School of Environmental Science and Management at UCSB is working on a wide range of exciting water policy and management issues. Projects range from water management strategies in the context of climate change, to analysis of the energy-intensity of water systems, to scenario analysis and much more.

One of our recent projects looked at different scenarios for water supplies for Southern California based on the 2005 State Water Plan and the 2005 Urban Water Management Plans. We chose the top three water supply sources for the next quarter century from the state water plan: urban water use efficiency, groundwater management, and reuse. The project was a collaborative with David Groves at the RAND Corporation, and we used the same model David developed for the State Water Plan, applying a scenario analysis in an approach along the lines that many businesses use-exploring a series of plausible futures. For example, what if we did more storm water capture in certain areas, or gained additional cost-effective efficiency improvements, or reclaim more waste water? What would that future look like? We compared these scenarios to some of the urban water management plans.

Of course, there's no one right answer, but doing this kind of analysis helps inform discussions about options. It looks like the state plan might be a bit conservative in terms of the potential for local water supply development from these three sources, and that's based on what many of the member agencies in MWD are already doing. Many agencies have aggressive strategies that go well beyond the overall forecast. Water managers are moving ahead in ways that may exceed the state plan to the advantage of both the economy and the environment.

We're working on a number of other projects, such as an analytical tool to support a more comprehensive cost-benefit analysis of desalination options so that one can calibrate investments in different water-supply options by factoring in externalities and come up with a portfolio that reflects both economic and environmental values.

I should note that the Water Policy Program often collaborates with partners on projects. The partners range from local, state, and federal agencies, to the California Urban Water Conservation Council, the RAND Corporation, Malcolm Pirnie, Stratus Consulting, NRDC, and Western Resource Advocates. These collaborations allow us to bring our outstanding graduate students together with experts and practitioners from government, business, and NGOs.

Santa Barbara chose decades ago not to connect to the State Water Project with the intent of controlling growth by controlling water. Did that work?

It seems that it did for a while. Actually, the community ultimately voted about a decade and a half ago to connect to the State Water Project. During the drought the community voted both for an ocean desal plant, which we built but then promptly disassembled, and to connect to the State Water Project. In hindsight, it's not clear that we needed to do either of those things. They provide a measure of "insurance" at a significant cost.

How did connecting to the State Water Project affect growth and water supply in Santa Barbara?

There has been some growth based on the availability of additional water. But we don't tap the state water system unless we really need it. It takes a great deal of energy (and therefore cost) to pump water from the Delta, down the Central Valley, over the Coastal Range, and down to Santa Barbara. We take it as kind of a last resort. And we've had ample supplies locally. There are still questions as to exactly what one could expect from different systems in a long-term statewide drought or major system disruptions, so I'm not sure whether in the long run this move really improved reliability that much.

Lastly, if investment in transportation infrastructure was the focus of 2006, will the next couple of years likely be more focused on water supply and reliability?

There are significant infrastructure needs in California related in part to population growth and changes in the economy. The voters have once again supported bond funding to provide some of the support to meet these needs.

The real debate is what infrastructure is needed. If we consider, for example, improvement in groundwater recharge systems and in the capacity to treat and deliver recycled water and improve water use efficiency in the same analysis as additional storage and interbasin transfers, it's interesting to look at the range of options for infrastructure investments and where the state would get the best bang for the buck.

Yes, there are infrastructure needs and there are a number of ways to meet water needs, and I welcome the debate in terms of the pros and cons and what's best for California.