Dams and desalination

California needs both

By Edward Ring
June 14, 2021

When Californians can take showers, without flow restrictors, for as long as they want, and when Californians can have lawns again instead of rocks and cacti in their front yards, water infrastructure in California will once again be adequate.

When California’s farmers can get enough water to grow food, instead of watching their suddenly useless holdings of dead orchards and parched furrows get sold for next to nothing to corporate speculators and subsidized solar farm developers, water infrastructure in California will once again be adequate.

One of the difficulties in forming a coalition powerful enough to stand up to the corporate environmentalist lobby in California is the perception, widely shared among the more activist farming lobby, that desalination is more expensive than dams.

That’s not true. It depends on the desalination, and even more so, it depends on the dam.

As a baseline, consider the cost of desalination in California’s lone large scale operating plant in Carlsbad north of San Diego. The total project costs for this plant, including the related pipes to convey the desalinated water to storage reservoirs, was just over $1.0 billion. At a capacity to produce 56,000 acre feet per year, the construction cost per acre foot of annual capacity comes in just over $17,000.

When it comes to the price of desalinated water, payments on the bond that financed the construction costs form the overwhelming share of the cost per acre foot.

For example, California’s second major desalination project, the proposed plant in Huntington Beach, will have a total project cost of $1.3 billion. Similar to Carlsbad, this plant will produce 50 million gallons of fresh water per day. A 20 year bond paying 7 percent will require annual payments of $122 million. That payment, applied to the hundred cubic foot increments, or CCF, that typically appear on a consumer’s water bill to measure their consumption, comes up to $5.03. By contrast, the cost per CCF for the desalination plant’s operating expenses is only $0.41, and the price per CCF for a desalination plant’s electricity consumption (at $0.10 per kilowatt-hour) is only $1.08. Initial construction costs, comprising 77 percent of the price of desalinated water, are the only reason desalination is considered expensive.

Compare this to the price of water from reservoirs, keeping in mind that paying off the construction costs for the dams are also the biggest variable in determining how much consumers have to pay for that water. With dams, unlike desalination plants, two factors come into play: the storage capacity, and the annual yield. With desalination plants the yield is up to the managers. Run the plant, out comes fresh water. With dams, how much water is released from the reservoir to downstream consumers in any given year depends on rainfall.

For this reason, the average annual yield of the reservoir is the most accurate way to measure its cost effectiveness. And this amount can vary widely. One of California’s biggest proposed new projects is the Sites Reservoir. It would be situated in a valley west of the Sacramento River, north of the Delta. As an off-stream reservoir, it would have water pumped into it when storm runoff is causing flooding. A twin to the already existing San Luis Reservoir, located west of the California Aqueduct south of the Delta, the Sites would have a capacity to store 2.0 million acre feet. But its yield is estimated at 500,000 acre feet per year.

In the case of the Sites Reservoir, this compares favorably to desalination. The Sites project is estimated to cost $5.0 billion, so the construction cost per acre foot of annual capacity comes in at $10,000, better than desalination at $17,000.

On the other hand, the case of the proposed Temperance Flat Reservoir is not so clear. The estimated cost for this dam is $2.6 billion and the planned storage capacity is 1.3 million acre feet. So far so good. But while estimates vary, the most optimistic projected average annual yield is around 100,000 acre feet per year. This equates to a construction cost of $26,000 per acre foot of annual capacity, considerably worse than desalination.

Does the fact that desalination yields a better return on construction costs than Temperance Flat mean that the Temperance Flat Reservoir project should be abandoned? Not necessarily. Back in 2017, during record rains, the San Joaquin River flooded, and that water – desperately needed by San Joaquin Valley farmers – could have still been in that reservoir and available for use today. The advantage of big surface storage reservoirs is not their return on capital investment, it’s that they can prevent flooding in wet years, and hold massive quantities of water in reserve for dry years.

Similarly, foes of desalination point to the more cost-effective Sites Reservoir proposal as evidence that desalination is too expensive. But the productivity of desalination is impervious to droughts; the water just keeps coming, year after year, no matter what. And the electricity required to run desalination, while significant, is no greater than the electricity currently used by a series of massive pumping stations necessary to transport water from north to south, over the mountains, and into the Los Angeles Basin – over 2.5 million acre feet per year.

Infrastructure development in California has been paralyzed by litigation and legislation. The result is a self-imposed scarcity of water that can be solved by an all-of-the-above strategy to develop new dams and desalination plants. Civilization requires a footprint, a plain fact that wasn’t lost on previous generations. We’ve learned how to mitigate the worst impact of new infrastructure, but cannot let the ideals of ecological perfection be an excuse to impoverish ourselves.

General obligation bonds to defray the cost to farmers and residents are something the people of California might accept. Then if the rains don’t come for years on end, Californians will still be able to purchase food grown in-state, and enjoy more of the normal amenities of life – a long hot shower. A healthy lawn.

This article originally appeared in the California Globe.

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