Why Los Angeles dropped 96 million black balls into drinking water
What are the black balls dropped into Los Angeles' drinking water? Reducing evaporation during California's drought Preventing the formation of bromate Keeping algae, birds and
What are the black balls dropped into Los Angeles' drinking water? Reducing evaporation during California's drought Preventing the formation of bromate Keeping algae, birds and debris under control Why not simply build a roof? How were the shade balls installed? Did the plastic contaminate the drinking water? What happened to the shade balls? A simple idea that attracted worldwide attention Millions of black plastic balls floating on a drinking water reservoir might sound like an environmental disaster, but for Los Angeles, they became an ingenious solution to several major challenges. The unusual sight attracted worldwide attention and left many wondering why a city would deliberately cover its water supply with 96 million plastic spheres. Far from being a publicity stunt, the floating "shade balls" were introduced by the Los Angeles Department of Water and Power (LADWP) to conserve water during California's severe drought, protect drinking water quality and meet strict environmental regulations. The project went on to become one of the world's most innovative and cost-effective examples of modern water management.The black balls are hollow plastic spheres known as shade balls, each measuring about 10 centimetres (4 inches) in diameter. Made from high-density polyethylene (HDPE), a durable plastic commonly used in water pipes and milk bottles, each ball contains a small amount of water to keep it stable and prevent it from being blown away by strong winds.The Los Angeles Department of Water and Power (LADWP) released all 96 million shade balls into the Los Angeles Reservoir in August 2015, completing what was then the world's largest shade ball project.
The carbon black coating protects the plastic from ultraviolet (UV) radiation, giving the balls an expected lifespan of around 10 years.The Los Angeles Reservoir covers approximately 175 acres (71 hectares). Engineers calculated that around 96 million shade balls were needed to cover most of the water's surface. Rather than forming a rigid layer, the balls float freely and automatically adjust as water levels rise and fall. Together, they create a protective blanket that blocks sunlight while allowing the reservoir to continue operating normally.One of the project's primary objectives was to conserve water. Southern California frequently experiences prolonged droughts, and large open reservoirs lose significant amounts of water through evaporation under intense sunlight. By shading the surface, the balls reduce the amount of solar energy reaching the water, helping to minimise evaporation. LADWP estimated that the project could save approximately 300 million gallons (around 1.1 billion litres) of water each year, enough to supply thousands of households annually.While saving water was important, protecting drinking water quality was an even greater priority. The reservoir contained naturally occurring bromide, which can react during the water treatment process. After water is disinfected using ozone, exposure to sunlight can convert bromide into bromate, a chemical classified as a possible human carcinogen by the International Agency for Research on Cancer (IARC). Because California has strict limits on bromate levels in drinking water, blocking sunlight significantly reduced the likelihood of this reaction occurring.The shade balls provided several additional benefits.
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