Talks to Watch

Why Are 96,000,000 Black Balls on This Reservoir?

112.9M views · May 10, 2019 · 12:07 · 2 HN recommenders · 6 mentions · discussed 2019–2025

Veritasium rides a boat across the Los Angeles reservoir covered in 96 million black plastic balls. He explains why they were really introduced, which was not primarily to reduce evaporation.

Why Hacker News points people here: Referenced as the explanation of shade balls and used in discussions of evaporation and floating covers.

“I thought the engineering at play here was pretty interesting.”HN comment, 2019

What Hacker News said 6

Recommendsel_benhameenMay 2019

“I thought the engineering at play here was pretty interesting.”

Shade balls on LA reservoir.

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In a sort of related/inverse vein, I thought the engineering at play here was pretty interesting. 96 million shade balls on a public water supply reservoir: this video

in “A Norwegian town built a giant mirror to deflect the sun (2017)” · view on HN
RecommendsTyrannosaurNov 2022

“Veritasium video about Los Angeles' reservoir black spheres project.”

Explains why LA's shade balls are black.

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this video Veritasium video about Los Angeles' reservoir black spheres project. They used black because - The goal was light-blocking more than anything else; black worked best - The black pigment held up to the environment (especially UV degradation) better than anything else they tried I expect the second point was the most important thing. Black plastic is very stable.

in “Floating solar panels that track the Sun” · view on HN
Cites itguerrillaNov 2021

“Or float those plastic balls [1] on it”

Floating balls reduce reservoir evaporation.

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Or float those plastic balls [1] on it, like they do for some reservoirs to stop evaporation. It'd take a lot of them, but that'd work and could be both cheaper and more permanent. 1. this video

in “A man who shoots at birds to keep them off a toxic pit [video]” · view on HN
Cites itwolfram74Jun 2022

“reducing solar driven evaporation in the same vein as this[0]”

Shade balls reduce solar-driven evaporation.

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The article describes artificial reservoirs as the water body of choice, which are less complex (partly because they already destroyed the ecosystem that was there) than naturally forming lakes, and has the added benefit of reducing solar driven evaporation in the same vein as this[0] [0] this video

in “US Army deploys its first floating solar array” · view on HN
Cites itthamerDec 2023

“Their use in Los Angeles was covered in a Veritasium video that was all over YouTube for a while (97M views)”

Covers LA shade balls used to prevent evaporation.

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Shading is used in California to prevent evaporation, see for example the well-documented use of "shade balls": link Their use in Los Angeles was covered in a Veritasium video that was all over YouTube for a while (97M views): this video The estimate given when they were added in 2015 – in the middle of a record drought – was that they would prevent the loss of 300 million gallons of water each year.

in “Largest Floating Solar Power Plant Taking Shape on Hydropower Plant” · view on HN
Cites itvanderZwanNov 2025

“Shade balls[0] could work”

Shade balls as a cooling idea.

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I think that's the wrong way round: climate change causes longer summers and shorter winters, so the problem is one of cooling, not heating. Shade balls[0] could work, but then they'd have to cover part of the lake with that. EDIT: And of course, that also comes with a reduction in total light reaching the lake, which may have different side effects beyond temperature alone. [0] this video

in “Mixing Is the Heartbeat of Deep Lakes. At Crater Lake, It's Slowing Down” · view on HN