California drought: Are rain barrels really a good idea?

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As California embarks on its likely fourth year of drought, communities up and down the Golden State are pledging to do more with local water sources — including whatever rain might fall from the sky.

On the macro level, cities like Los Angeles are looking to re-plumb their storm drains to direct more rainfall to underground aquifers. On the mirco level, residents are encouraged to adopt a similar strategy with the poster boy of all drought-busters: the rain barrel.

But are rain barrels worth the cost?

Maybe not, according to UC Davis engineering professor Jay Lund, in a new post on his California WaterBlog, “The Romance of Rain Barrels.” 

With the word romance, Lund admits that the general public's love of rain barrels is growing. They’ve gotten more popular around California since 2014, the drought’s beginning.

In Los Angeles, their rise goes back to at least 2009, when the Department of Water and Power and the Department of Sanitation co-sponsored the first test run of the concept, in Mar Vista and Hollywood.

These days, city dwellers are swooning for storm water. A thousand rain barrels offered by the city in November disappeared in a blink. Mayor Eric Garcetti announced that the rebate for more would bump up from $75 to $100, and residents claimed 400 more, quickly

But Lund seems to suspect that Californians' ardor for rainwater capture is throwing off their judgment – and he offers “back of the envelope” calculations to prove it. Given that rain barrels cost $100 and store only around 50 gallons at a time, by the traditional water measurement of acre-feet (an acre-foot is the amount of water it would take to cover one acre of land with one foot of water, enough for about 2-3 households), he argues, rain barrels are expensive relative to other options.

He places the cost of an acre-foot of rain barrel water at $652,000, compared with only $2,000 an acre-foot as an estimated cost for expanding storage capacity at large upstream dams. Lund continues:

For a typical home in coastal California, the annual pattern of storms might allow filling and emptying a 50-gallon cistern one to three times (with considerable overflow possible each time), yielding 50 to 150 gallons a year – less than 0.1 percent of a household’s annual water use in California. For inland homes, the actual water produced would be much less because the rain barrel is capturing runoff that likely would have been used by others downstream anyway.

His verdict on the economics of rain barrel water? “Unattractive.”

Versions of that analysis have cropped up among rainwater skeptics since the drought started, including some who’ve written in to comment on our stories. So I asked TreePeople’s policy director, Deborah Weinstein-Bloom, if she thought loving rain barrels was wrong.

Weinstein-Bloom counters that Lund is underestimating the collateral benefits to storm water capture, including pollution reduction and flood control. “If we capture the first 3/4 inch, the "first flush," which is generally the most contaminated precipitation that heads out to our rivers and ocean, capturing this “first flush" can also help prevent flooding,” she says.

And she offers prices far lower than Lund’s. She finds support in numbers from the Los Angeles Department of Water and Power’s Stormwater Capture Master Plan. The DWP’s consultants calculate the cost of local rainwater harvest between $1,000 per acre-foot for direct use in some conditions, and $14,000 in less favorable scenarios – still lower than Lund’s view, but sometimes higher than even the expensive stuff – water sourced from desalination plants.

Weinstein-Bloom argues that L.A. is already bearing costs that are “beyond reconciliation” for importing 89 percent of our water – not just the price of bringing the water here itself, but also the greenhouse gas emissions and the economic loss inherent in outsourcing water supply work to other regions.  

“What TreePeople would like to see, as in Australia after its 12-year drought, is for captured rainwater to be used for indoor, non-potable purposes such as in toilets, laundry and even for hot water heaters,” she says.

That idea remains a long way off from practicality. And Los Angeles’ rain barrels aren’t exactly the same as Australia’s; the average home water tank there is more often 5,000 gallons than 50, which makes comparisons about the economic efficiency of these systems a little apples-to-watermelons.

But both Weinstein-Bloom and Lund seem to agree that even if rain barrels are not large volumetrically, they're meaningful emotionally. And so, with Valentine’s Day around the corner, maybe they’re not that different. Maybe they’d agree that there’s nothing wrong with a little romance after all.   

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