Environmental Economics

Facing a long-term water crisis, officials concerned with preserving a reservoir in Los Angeles hatched a plan: They would combat four years of drought with 96 million plastic balls.

On Monday, Mayor Eric Garcetti of Los Angeles arrived at the 175-acre Los Angeles Reservoir to release the final installment of the project: 20,000 small black orbs that would float atop the water.

The scene resembled something found at a playground — “You turned the reservoir into the world’s largest ball pit? #bestmayorever,” wrote one supporter on the mayor’s Facebook page — but the initiative has serious implications for the city’s water supply.

Mr. Garcetti said that the dark balls would help block sunlight and UV rays that promote algae growth, which would help keep the city’s drinking water safe. Officials also said the balls would help slow the rate of evaporation, which drains the water supply of about 300 million gallons a year. The balls cost $0.36 each and are part of a $34.5 million initiative to protect the water supply.

In a video posted on Monday to Facebook, an official is heard saying, “2, 1 … Shade balls away!” A moment later, the remaining balls skitter down a slope, heading for the reservoir.

via www.nytimes.com

Hmmmm…that's creative.  But is it worth it? Let's do some fuzzy blog-math (which I am sure is wrong):

At $0.36 per ping pong ball, the 96 million balls cost $34.5 million.  According to my in-depth blog-qualified research (a Google search on Los Angeles evaporation rates), LA swimming pools lose water at about 5.46 feet per year due to evaporation.  According to the article above, the LA reservoir is about 175 acres, or 7,623,000 square feet. 

Using these as blog-park figures, without balls the LA reservoir would lose about 41,621,580 cubic feet of water per year due to evaporation (that's 311,351,040 gallons per year). I am going to assume that once LA exposes their balls to the water, no water evaporates.

The article doesn't give any information on how long the balls last, so to be conservative I am going to assume they only last a year (my guess is they last longer, but I don't want to assume anything…stop laughing).  So a top end estimate is that the LA water ball project costs about  $0.11 per gallon per year.   Obviously, (insert condescending duh! here) if the balls last more than one year, the per gallon cost decreases.

Now we just need a benefit (willingness to pay?) per gallon for comparison.  I am tempted to use the price of water in LA as a benchmark, but California water pricing is so screwy that I doubt prices have any correlation whatsoever with benefits (water prices in CA are ridiculously low). Maybe I could use the price of bottled water (but they are ridiculously high).  Rather than guess, I will just leave the conclusion to our trusted readers and hope David Zetland decides to weigh in…if the value of water is greater than $0.11 per gallon then it looks like the putting balls in the water is beneficial.

*Sometimes my headlines write themselves