Shade balls represent a unique engineering solution designed to address various challenges in water management. These floating spheres have gained attention for their application in large water bodies, offering a method to protect and conserve water resources.
What Shade Balls Are
Shade balls are small, hollow plastic spheres that float on the surface of water. They typically measure about four inches (approximately 10 cm) in diameter. These balls are primarily made from high-density polyethylene (HDPE), a durable plastic also used in food and beverage containers.
The balls are usually black due to the addition of carbon black, which serves as a UV-stabilizing agent. This black color is crucial for their function and contributes to their longevity. When deployed, millions of these balls can cover extensive water surfaces, forming a continuous layer.
Why Shade Balls Are Used
Shade balls are primarily deployed to address specific problems in open water reservoirs. One significant purpose is to reduce water evaporation. By covering the water’s surface, they significantly decrease exposure to direct sunlight and wind, which are major contributors to water loss. Studies indicate that shade balls can reduce evaporation by a substantial margin, often cited as 80% to 90%.
Another application involves preventing harmful algal blooms. Algae require sunlight for photosynthesis and growth. By blocking light penetration into the water, shade balls inhibit the proliferation of algae. This not only maintains water quality but also reduces the need for chemical treatments that might otherwise be used to control algal growth.
Additionally, shade balls limit certain chemical reactions within treated water. In drinking water reservoirs, they reduce the formation of bromate, a byproduct that can occur when bromide and chlorine react under sunlight. By blocking ultraviolet (UV) exposure, shade balls help mitigate the creation of this compound, thereby contributing to public health protection.
How Shade Balls Work
Their dense coverage and black color are instrumental in blocking sunlight from reaching the water below. This prevents solar radiation from heating the water, which is a primary driver of evaporation. The reduction in light also directly inhibits the photosynthetic processes necessary for algal growth.
The layer of balls also acts as a physical barrier. This barrier significantly reduces the water’s surface area directly exposed to wind. Wind can accelerate evaporation by continuously removing the layer of moist air above the water, so minimizing this contact helps conserve water.
Moreover, blocking sunlight helps moderate the water temperature. Even though the black balls absorb heat on their surface, the air trapped inside them acts as an insulating layer. This insulation means less heat is transferred to the water, helping to maintain a cooler, more stable water temperature. A cooler water body naturally experiences less evaporation and can be less conducive to certain microbial growths.
Environmental Aspects of Shade Balls
Shade balls are manufactured from high-density polyethylene (HDPE), which is a food-grade plastic. This material is selected for its durability and resistance to UV degradation, ensuring the balls can withstand prolonged exposure to sunlight and harsh environmental conditions. Their expected lifespan is typically around 10 years or more.
At the end of their operational life, shade balls are designed to be recyclable. This allows for the material to be processed and potentially reused, contributing to a more circular economy.
However, the production of shade balls involves an energy and water footprint. The manufacturing process for HDPE requires resources like oil, natural gas, and electricity, which are water-intensive. While shade balls save water during their deployment, some analyses suggest it can take a period of one to two and a half years, or longer depending on conditions, for the water saved to equal the water consumed in their production. Concerns have also been raised regarding the potential for microplastic shedding or the leaching of chemicals over time, although the HDPE material used is generally considered inert and safe for drinking water contact.