Why Shade Balls Are Critical for LA Reservoir's Water Quality and Supply | Veritasium Info

Discover the Science Behind Shade Balls in LA Reservoir and Their Impact on Water Evaporation, Algae, and Bromate Formation

Explore the role of shade balls at LA Reservoir. Learn how these black plastic balls reduce evaporation, prevent algae growth, and combat the formation of carcinogenic bromate in Los Angeles' water supply.


Veritasium Info: Understanding the Role of Shade Balls in Water Conservation and Safety

In Los Angeles, a unique solution has been implemented to address water conservation and safety issues at the LA Reservoir. These black plastic spheres, known as shade balls, are floating on the water’s surface in vast numbers. But contrary to popular belief, their primary purpose is not to reduce evaporation. In this article, we explore the true function of these shade balls, their effectiveness, and their impact on water quality.


What are Shade Balls?

Shade balls are large black plastic balls that are deployed in water reservoirs. They are made from a material called high-density polyethylene (HDPE), the same type of plastic used in milk jugs. These balls are designed to float on the surface of water bodies like the LA Reservoir, covering large areas and providing shade to the water beneath.

Initially, shade balls were used in other applications, such as preventing birds from landing on ponds containing mine tailings and on water bodies near airports to protect wildlife and prevent interference with aircraft. However, when the LA Reservoir faced a water quality issue involving bromate formation, shade balls were found to be an effective solution.


The Purpose Behind Shade Balls in LA Reservoir

The LA Reservoir serves as a crucial water source for the city, providing a significant portion of Los Angeles' water supply. However, the water contains a naturally occurring substance called bromide, which, when exposed to chlorine and sunlight, forms a potentially carcinogenic compound known as bromate. To prevent the formation of bromate, which could endanger public health, a solution was needed to block sunlight from reaching the water.

The solution came in the form of shade balls. When scientists at the LADWP (Los Angeles Department of Water and Power) tested various methods to block sunlight from the reservoir, they found that shade balls were the most effective and affordable option. These black plastic balls absorb sunlight, preventing it from reaching the water and triggering the harmful chemical reaction that forms bromate.


How Shade Ball Work

Shade balls are designed to cover the water surface and block sunlight from reaching the water. Their black color is key to their functionality, as it helps absorb the sunlight, preventing the water from reacting with chlorine and bromide to form bromate. The material used to make the shade balls is safe for contact with drinking water and is stable enough to withstand exposure to sunlight for years.

Interestingly, despite their dark color, shade balls have a cooling effect on the water. While the balls absorb heat, the air inside the balls acts as an insulator, preventing the heat from transferring to the water beneath. This results in a slight reduction in water temperature, further reducing evaporation rates.


The Impact on Water Quality

One of the primary concerns with open water reservoirs is the growth of algae. In the past, algae outbreaks would cause discoloration in the water, making it appear slightly green. However, since the deployment of shade balls, the algae problem has been significantly reduced. The lack of sunlight has effectively stopped algae from growing, which has led to improvements in water quality.

Additionally, the shade balls help reduce the need for chlorine. In the past, high levels of chlorine were added to the water to control algae growth, but with the shade balls in place, the water has remained clear with minimal chlorine usage. This not only improves the taste and quality of the water but also reduces chemical costs for the city.


Evaporation Reduction and Water Conservation

One of the most widely discussed benefits of shade balls is their ability to reduce evaporation. In a city like Los Angeles, where water is scarce, minimizing water loss through evaporation is crucial. The shade balls cover approximately 80-90% of the reservoir’s surface, which significantly reduces the amount of water that evaporates into the air.

Although the shade balls themselves absorb heat, they do not increase the rate of evaporation. In fact, the balls’ insulating properties help maintain a cooler temperature in the water below, further reducing evaporation. The use of shade balls in the LA Reservoir has proven to be an effective method of conserving water in a region where every drop counts.


Addressing Public Concerns

Despite the benefits of shade balls, some concerns have been raised regarding their use. People have questioned whether the plastic balls are safe for drinking water and whether they might leach harmful chemicals into the water over time. However, the shade balls are made from food-grade plastic and are thoroughly tested to ensure that they do not pose a risk to public health. The material used in the balls is inert, meaning it does not react with the water, and it has been proven to be safe for long-term exposure to sunlight.

Another concern is the visual impact of the shade balls, which cover the surface of the reservoir in a seemingly chaotic pattern. Some people have compared the sight to a giant ball pit or wondered if the balls might interfere with boat navigation. However, as one of the reservoir workers explained, the balls are designed to stay in place even during high winds, and their shape ensures that they do not interfere with the reservoir’s operations.


Conclusion: The Science Behind Shade Balls

The shade balls in the LA Reservoir provide a fascinating example of how science and innovation can be used to solve real-world problems. By preventing the formation of bromate, reducing evaporation, and improving water quality, these black plastic balls have proven to be an effective solution to several water-related challenges in Los Angeles. While they may appear simple, the science behind shade balls demonstrates the power of physics and environmental engineering in addressing complex issues such as water conservation and safety.

With over 96 million shade balls in the LA Reservoir, this project has not only helped to improve water quality but also contributed to the city’s overall water conservation efforts. As more cities face similar challenges related to water supply and quality, the success of shade balls in Los Angeles may serve as a model for other regions looking for innovative solutions to preserve and protect their water resources.


Frequently Asked Questions (FAQs)


Q1: What exactly are these "shade balls" I've heard about? 

A1: Shade balls are large, black plastic spheres made from high-density polyethylene (HDPE), the same durable plastic used in milk jugs. They are designed to float en masse on the surface of water reservoirs.

Q2: What was the primary reason for deploying shade balls in the LA Reservoir? 

A2: The main goal was to prevent the formation of bromate, a potentially carcinogenic compound. Bromate forms when naturally occurring bromide in the water reacts with chlorine and sunlight.

Q3: How do the shade balls stop bromate from forming? 

A3: Their black color is key; it allows them to absorb sunlight, effectively blocking it from reaching the water. This prevents the chemical reaction between bromide and chlorine that leads to bromate.

Q4: Do the black shade balls actually make the water cooler, or do they heat it up?

A4: Surprisingly, they have a cooling effect. While the balls absorb heat, the air inside them acts as an insulator, preventing that heat from transferring to the water below. This actually helps reduce the water's temperature slightly.

Q5: Besides preventing bromate, how else do these shade balls improve water quality?

A5: They significantly reduce the growth of algae by blocking the sunlight that algae need to thrive. This leads to clearer water and reduces the need for large amounts of chlorine, improving the overall taste and quality.

Q6: Are shade balls effective in conserving water? 

A6: Absolutely. By covering approximately 80-90% of the reservoir's surface, they significantly reduce the amount of water that evaporates into the atmosphere, which is crucial for water-scarce regions like Los Angeles.

Q7: Is it safe to have plastic balls in drinking water? Could they leach harmful chemicals? 

A7: Yes, they are considered safe. The shade balls are made from food-grade plastic and undergo thorough testing to ensure they are inert, meaning they don't react with or leach harmful chemicals into the water.

Q8: Were these shade balls developed specifically for the LA Reservoir? 

A8: Not entirely. While they were a perfect solution for the LA Reservoir's specific issue, shade balls had prior applications, such as preventing birds from landing on industrial ponds and near airport runways.

Q9: Just how many shade balls are in the LA Reservoir? 

A9: There are over 96 million shade balls floating on the surface of the LA Reservoir.

Q10: Do the shade balls move around, or interfere with reservoir operations, especially in windy conditions? A10: 

No, they are designed to stay in place even during strong winds. Their shape and collective mass ensure they do not interfere with the reservoir's operational functions.

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