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California Fights Drought With 96 Million "Shade Balls"
HughPickens.com writes: Katie Rogers writes in the NY Times that the city of Los Angeles is releasing 96 million plastic "shade balls" into the 175-acre Los Angeles Reservoir to help block sunlight and UV rays that promote algae growth, which would help keep the city's drinking water safe. Officials also say the balls will 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. Shade balls are the brainchild of Brian White, a biologist with the utility who based the idea on "bird balls" that he observed in waterways near airport runways to prevent airfield bird strikes. The Los Angeles Reservoir, which holds 3.3 billion gallons, or enough water to supply the city for up to three weeks, joins three other reservoirs already covered in the shade balls. "In the midst of California's historic drought, it takes bold ingenuity to maximize my goals for water conservation," says Mayor Eric Garcetti who was at the Los Angeles Reservoir to mark the addition of 20,000 of the small balls to the lake. "This effort by LADWP is emblematic of the kind of the creative thinking we need to meet those challenges."
To the extent the point was to keep heat away from the water, I wonder why they didn't go for something with a high albedo instead of black.
My thought as well. I suspect it has to do with black plastic being more resistant to UV degradation.
They reportedly considered a floating shade cloth, but found this to be a cheaper solution when all costs were factored in.
Why is it cheaper? Don't ask me. But it reportedly is.
IMHO, the "ideal" solution would probably be to use the area over the water for productive purposes, such as floating sealed algae farm or floating solar farm, so that you're both stopping evaporation and getting a secondary benefit with the same system. But the overhead times and costs would obviously be much higher for that.
I'll never forget the last thing grandma said to me before she died: "What are you doing in here with that knife?!?"
Why limit ourselves to only one color? Make a bicolored ball, slightly heavier on the black side. There you go, efficient at blocking heat during the day but also efficient at allowing the water to radiate it away at night.
:)
I think, though, the first response to this thread nailed it - They chose black for the same reason power, phone, cable, and virtually every other type of exterior grade wiring comes primarily in black - UV resistance. Probably not a good idea to put 96 million rapidly deteriorating sources of pollution into a reservoir.
For the 1989 Movie The Abyss James Cameron shot the underwater sequences for the film were shot at an unfinished Cherokee Nuclear Power Plant, situated outside Gaffney, South Carolina, which had been abandoned by Duke Power. Two specially constructed tanks were used. The first one held 7.5 million US gallons (28,000 m3) of water, was 55 feet (18 m) deep and 209 feet (70 m) across. At the time, it was the largest fresh-water filtered tank in the world. Additional scenes were shot in the second tank, which held 2.5 million US gallons (9,500 m3) of water. The filmmakers had to figure out how to keep the water clear enough to shoot and dark enough to look realistic at 2,000 feet (700 m), which was achieved by floating a thick layer of plastic beads in the water and covering the top of the tank with an enormous tarpaulin.
Today's vices may be tomorrow's virtues.
They are creating an environment for an algae bloom that are starting to cause problems everywhere.
And yet, they've been using shade balls since 2008 without incident. (See Ivanhoe reservoir.) You'd think that would be an easy problem to spot.