Los Angeles has dumped something like 90 million black balls in a reservoir to reduce evaporation.
Why would they use black which absorbs light and gets warm, and not white which does less so?
White plastic breaks down very quickly in sunlight. UV-resistant additives are available, but they’re usually black - hence the black plastic balls.
More information in XT’s IMHO thread here.
My guess is that black balls won’t show the algae and mold that is bound to grow on them. And the extra evaporation due to the darker color is probably minimal compared to the savings due to the balls.
I want to know if the color blue was even considered.
They’re simply purchasing an off the shelf item. You can have any color you want as long as it’s black.
From the manufacturer’s website:
“Another use for our floating covers is to prevent the growth of algae. AWTT covers are opaque to sunlight. This inhibits the growth of algae and other water plants. Using an evaporation control cover will not only retain precious water volumes but will also help prevent the contamination of water through the growth of plants and algae.”
The black color is opaque. That’s the point.
How long until the first body is dumped under the balls?
I’m not sure that color matters greatly in reducing water loss by evaporation. The floating balls simply reduce the exposed water surface area. They probably shelter the surface from wind-aided evaporation as well.
I’ve seen them used to cover ponds near airport flight paths to discourage waterfowl from interfering with aircraft, so we called them bird balls. I hope LA has plans to install a fence downwind to corral the balls that the wind will blow away.
Sorry, but the thread title ‘Black Balls: Los Angeles Reservoir’ sounds so much like an entry in a 70s Blaxploitation / Porno series*!* :eek:
OP Here.
I could understand that if you put a sheet of plastic over the reservoir, then water couldn’t evaporate. Or would it ‘steam’ and evaporate around the edges anyhow? But the black balls won’t form a complete cover. I would think the added solar heating of the balls, transferred to the top layer of the water, would result in increased evaporation. Perhaps the actual ‘open’ area is so small that on balance its an improvement.
I wonder why they didn’t use HexProtect, available from the same manufacturer. The hex one is supposed to cover even more of the surface.
I would think the added solar heating of the balls,
You’re assuming that black plastic balls absorb more heat than open water and I seriously doubt that. Water is especially good at absorbing red and infrared wavelengths. I suspect the net effect of the balls is to cool the water.
I agree, the dead air in the balls is a good insulator. Even if the sun-facing side warms up, air is a poor medium to transfer that heat to the water on the bottom of the balls.
A sheet would be slightly more effective, but the balls are like one tenth the cost.
This thread isn’t complete without the video. One might ask, “how did they get 90 million balls into the lake…”
It’s a rather simple and more elegant method than I was expecting…
Now we need to know how they got them into the trailer loose like that. Unless they stood that trailer straight up and poured them in.
There could have been an opening at the top of the shipping container as well. But I think your idea is correct - you can elevate a trailer all the way to straight up with the right equipment, right?
Perhaps it might have been harder to pour to them into the reservoir. The balls did do a good job of rolling down inclines and then spreading themselves out in the water.
Also, the balls automatically adjust up and down as the water level changes (unlike a sheet), that the balls adjust automatically to irregular shorelines (very difficult with a sheet), that you don’t need to support the balls in the middle of the reservoir, and possibly the balls allow a little bit of air exchange and so are cleaner, or the balls self-clean a bit as they rotate different sides up toward the sun.