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

Veritasium · 112.9M views · 2019-05-10 · 12:07

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Overview

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.

On Hacker News

Referenced as the explanation of shade balls and used in discussions of evaporation and floating covers.

Recommended by 2 HN people across 2 months · HN mentions 2019–2025

Topics

Environment, agriculture & food systemsCivil engineering & construction
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shade ballslos angeleswater engineeringevaporationveritasium

What people said

Tyrannosaur · 2022-11 · Recommendation

[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.

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el_benhameen · 2019-05 · Recommendation

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: [VIDEO]

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vanderZwan · 2025-11 · Reference

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] [VIDEO]

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Sources

Video by Veritasium, played through YouTube.

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