Here's an odd story: the city of Los Angeles has intentionally dumped thousands of black plastic balls in a local reservoir in order to protect the water supply.

The Los Angeles Department of Water and Power dumped 400,000 hollow-4-inch "Shade Balls" to cover the surface of the Ivanhoe Reservoir.

David Nahai, CEO and general manager of the utility, said in a news release: "These balls will shade the water's surface, helping to prevent a sunlight-triggered chemical reaction with the treated water, thereby ensuring its safety. Nothing tops water quality on our priority list. We are on the record with this priority and we will stop at nothing to ensure our water is safe."

The Shade Balls will stay on the reservoir for about five years, when a new underground water storage project is complete.

The balls help to minimize the risk of bromate-forming chemical reactions.

An Associated Press story describes the Shade Ball-covered reservoir as resembling "a giant tub of bowling balls or a piece of large-scale conceptual art."

For some cool photos of the Shade Balls being dumped into the reservoir, check out this Los Angeles Times local news blog.