Shade balls are small, buoyant spheres deployed on the surface of water reservoirs to safeguard water resources. These floating covers protect water supplies, particularly in regions where environmental factors can compromise water quality and quantity. They create a protective layer over open water bodies.
Addressing Water Loss and Quality
Shade balls address water loss due to evaporation and help maintain water quality. In large, open reservoirs, especially in arid climates, direct sunlight and wind can lead to substantial water evaporation. Shade balls create a physical barrier that significantly reduces this process, with estimates suggesting an 85 to 90 percent reduction in water lost to evaporation. This conservation effort is particularly important for regions facing water scarcity.
Beyond evaporation control, these spheres preserve water quality. By blocking sunlight, they prevent algae photosynthesis, which thrives in sunlit water. Algae blooms can degrade water quality, produce toxins, and increase the need for chemical treatments.
Shade balls reduce the formation of harmful chemical byproducts, such as bromate, a suspected carcinogen. Bromate can form when naturally occurring bromide in water reacts with chlorine, used for disinfection, in the presence of sunlight. By shielding the water from ultraviolet (UV) radiation, shade balls help prevent this chemical reaction, contributing to safer drinking water.
How They Work
Shade balls are effective due to their physical properties and deployment. Typically made from high-density polyethylene (HDPE), these spheres are about 4 inches (10 cm) in diameter and are often partially filled with water to ensure stability against wind. Their black color absorbs sunlight, preventing UV radiation from penetrating the water surface. This blockage of solar energy directly reduces the water’s temperature, slowing the rate of evaporation.
The continuous layer formed by millions of balls acts as a physical barrier, limiting direct contact between the water surface and the air. This reduces air exposure, minimizing the wind’s ability to carry away moist air and further decreasing evaporation. The opaque black HDPE material prevents sunlight from reaching deeper into the water column, inhibiting algae growth. The material is chosen for its durability and resistance to UV radiation, ensuring the balls can withstand prolonged outdoor exposure.
Broader Implications and Practicality
The widespread deployment of shade balls involves practical and environmental considerations. The spheres are made from high-density polyethylene (HDPE), a plastic commonly used for food and beverage containers, certified food-grade and safe for drinking water contact. However, manufacturing millions of these plastic balls requires significant resources, including oil, natural gas, and electricity, consuming substantial water. Some analyses suggest the water used in manufacturing the balls could exceed the water saved from evaporation over certain periods.
Environmental concerns include potential microplastic shedding and disposal or recycling of the balls after their estimated 10-year lifespan. While HDPE is recyclable, the sheer volume of balls deployed presents a logistical challenge for retrieval and processing. Critics question the aesthetic impact of covering large reservoirs with black plastic spheres and the possibility of chemical leaching, despite safety assurances. Deployment costs, though often presented as more economical than alternative reservoir covers, still represent a multi-million dollar investment.
Significant Use Cases and Legacy
The Los Angeles Department of Water and Power (LADWP) prominently deployed shade balls in its reservoirs. The concept originated from “bird balls” used to deter birds from landing on ponds near airfield runways. In 2008, LADWP placed approximately 400,000 shade balls into the Ivanhoe Reservoir to prevent bromate formation, a carcinogen that forms when sunlight interacts with bromide and chlorine.
The most significant deployment involved 96 million shade balls onto the Los Angeles Reservoir in 2015, aiming to improve water quality and reduce evaporation. This initiative reportedly saved around 300 million gallons of water annually and offered a cost-effective solution compared to other reservoir covering methods. While some reservoirs later replaced shade balls with floating covers, the Los Angeles Reservoir continues to use them for water quality compliance and evaporation control. Their use by LADWP highlights an innovative approach to water management, though their practicality and environmental footprint remain subjects of ongoing discussion.