Slashdot Mirror
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.
"... to help block sunlight and UV rays that promote algae growth,"
I browse on +1 so AC's need not respond, I won't see it.
It looks like these balls were first mass produced to block light, not to minimize evaporation, in order to reduce the formation of a carcinogenic byproduct of water chlorination of bromine-rich waters. So perhaps the color isn't ideal for its current role - but sufficient.
I'll never forget the last thing grandma said to me before she died: "What are you doing in here with that knife?!?"
Comment removed based on user account deletion
My guess would be that these are easy to transport and deploy. Pulling a cloth over means getting a boat and keeping it lined up. Also needs to be transported in one piece. Balls can be loaded into a dump truck, driven to any point around the reservoir, and just dumped in. They'll spread out by themselves.
And plastic balls are very cheap. These don't even need to be particularly good quality. Stamp them in a mould, glue two halves together, you're done.
It is a concrete reservoir used to hold TREATED water. There is nothing in it.
Why is it cheaper? Don't ask me. But it reportedly is.
The balls require no maintenance, aside from replacing lost or stolen balls. Nothing is really going to be damaging them out there besides the elements, which will work on them only slowly due to their nature. A cloth would just be an algae-growing substrate mat.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
Water is already a near-ideal absorber of sunlight, so the black balls shouldn't change much in that respect, except to keep much more of the heat on the surface. They are also quite likely much better heat radiators, which should be even more helpful since the heat will be more concentrated (hotter) and thus radiate far more rapidly.
I also don't know that wind would be a problem - it sounds like they're trying to pack these pretty tightly, so it's not like they're going to be able to freely roll around the surface and lift a film of fast-evaporating water. It'll take a heck of a wind to rotate them against each other, especially considering they're almost completely shielded from the force by their upwind fellows. So most of the time I would suspect they would remain relatively stationary, with their top surfaces getting very hot, and their plastic construction largely failing to conduct that heat down to the water's surface.
I do agree that white balls (preferably a beyond-visual solar white) would seem to be a considerably better solution at first glance, but I can think of several possible confounding factors:
- Longevity: As a rule plastic breaks down rapidly in direct sunlight. These are probably carbon-black, which I suspect is is about as good as it gets for both cost, UV protection, and non-toxicity. Alternate UV-protective dyes are likely to be more expensive, less effective, and more toxic. Plus the faster degradation would increase clean-up and replacement costs as the balls degrade.
- Costs: these balls are already mass-produced for other reservoir-related purposes: a new design would add at least some design and retooling costs
- Testing (money and time): these balls have already been used in reservoirs and thus (hopefully) the health and safety issues have received at least some study. Reformulate the balls and you'll need to do those studies again.
--- Most topics have many sides worth arguing, allow me to take one opposite you.
Rich people watering lawns is not the problem. Residential water use, ALL residential water use in California, accounts for about 4% of our annual use. It is unrestricted use by big agricultural concerns that use OVER 80% of our water. They still flood fields for christ's sake!!! Their is no incentive for them to use modern water wise farming practices since they have "senior rights" going back centuries. We can't even pass a law restricting them so now we grow rice in flooded fields. Just stupid.
This is a poorly-researched idea.
What is it with people here? Fucking armchair quarterbacks. No, you're not smarter than them. This isn't even the first time those balls have been used. You probably don't know that the main goal is reducing bromate production, because you haven't fucking clue. Oh and the water is chlorinated. If you'd done your own fucking research instead of just shooting your mouth of you'd know that. Sorry for all the swearing, but seriously, WTF is wrong with you?