Do Shade Balls conserve/save water?

Question

In recent headlines here, here, here, it appears that Los Angeles reservoir now has 96 million "Shade Balls" to slow evaporation.

I'm skeptical on a number of fronts:

• How much water went in to creating 96 million of these things?
• Do these things continue to be effective as the reservoir level rises/lowers?
• They're black, so they absorb heat and maybe transfer it to the water?
• They're round, so maybe the wind will "roll" them on the water, thus exposing thousandths of an inch of water to evaporation over the ball's surface area?

Answer 1

According to the company who makes these, XavierC LLC, they are basically the same idea as a pool cover.

1) How much water went in to creating 96 million of these things?

The manufacturing facility is in Colton CA though, so whatever water was used did come from a particularly drought-y part of the state.

Given the amount of water they're projected to save and the generally accepted effectivness of pool covers though, it's safe to assume they are overall saving water.

2) Do these things continue to be effective as the reservoir level rises/lowers?

That's the whole idea! From XavierC site:

By their nature, the conservation balls re-arrange themselves to fit any size and shape reservoir. As water levels drop the balls again accommodate the situation by stacking on themselves. When water levels rise the balls return to single layer on the surface.

Unlike a pool cover, a mass of balls will rearrange itself to cover whatever shape the surface area of the reservoir takes.

3) They're black, so they absorb heat and maybe transfer it to the water?

They are black, and they will absorb heat. Heat is not the issue.

Surface area, wind, and humidity all factor directly into evaporation rate, while temperature is an indirect factor (evaporation temp depends on wind, humidity, and surface area). Cutting off the water from air and wind has a far greater effect of evaporation.

4) They're round, so maybe the wind will "roll" them on the water, thus exposing thousandths of an inch of water to evaporation over the ball's surface area?

This is a stretch. Given the direct effect the wind has on evaporation rate, the few drops exposed by a ball rolling over would have less effect than lowering the requirements for evaporation.

Answer 2

The primary source of this claim is the LA City Council’s Energy and Environment Committee. The official website of LA Mayor's Office writes:

Holding a total of 3.3 billion gallons, enough to supply the entire city of Los Angeles for up to three weeks, the L.A. Reservoir is located in LADWP’s Van Norman Complex in Sylmar. At Monday’s event, Mayor Garcetti was joined byCouncilmember Mitchell Englander, LADWP General Manager Marcie Edwards and Marty Adams, LADWP Senior Assistant General Manager of the Water System.

“In the midst of California’s historic drought, it takes bold ingenuity to maximize my goals for water conservation,” said Mayor Eric Garcetti. “This effort by LADWP is emblematic of the kind of the creative thinking we need to meet those challenges. Together, we’ve led the charge to cut our city’s water usage by 13%, and today we complete an infrastructure investment that saves our ratepayers millions and protects a vital source of drinking water for years to come."

At $0.36 each, the shade balls require no construction, parts, labor or maintenance aside from occasional rotation. A second, $100 million ultraviolet treatment facility is due to break ground next -- allowing LADWP to meet regulatorytimelines, save more than $250 million in capital improvement costs and further reduce water losses.

“As the drought continues, it has never been more important to focus on innovative ways to maintain the highest quality drinking water for our 4 million residents, said Councilmember Mitchell Englander. “In addition to cutting back on the need to chemically treat our water to prevent natural occurrences like algae, these shade balls are a cost-effective way to reduce evaporation each year by nearly 300 million gallons, enough to provide drinking water for 8,100 people for a full year.”

Said Councilmember Felipe Fuentes, chair of the LA City Council’s Energy and Environment Committee: “LADWP’s innovative use of shade balls will protect our water supply and ensure that residents have access to clean, safe, and ready-to-drink water. As we work to ensure a more sustainable and resilient future for L.A., I look forward to more creative, trailblazing and cost-effective solutions.”

Mayor Eric Garcetti announces completion of innovative 'Shade Ball' cover project.

The claim was reblogged by many reputable sources. The Guardian reports:

The idea was conceived in 2007 in an effort to prevent the reservoir becoming contaminated with bromate, a substance formed when chemicals in the water react with sunlight. The balls are a relatively low-cost solution, at $34.5m, and are expected to save about $250m over 10 years, and prevent 300m gallons of water evaporating

96m water-saving shade balls released into LA reservoir

National Geographic News reports:

The balls cost 36 cents each, for a total of $34.5 million. The utility has been testing the concept since 2008, reporting that shade balls reduce evaporation by 85 to 90 percent. That should equate to saving nearly 300 million gallons a year, enough to provide drinking water for 8,100 people, said Los Angeles City Councilmember Mitchell Englander.

Why Did L.A. Drop 96 Million ‘Shade Balls’ Into Its Water?

The LA mayors site offers the following evidence for the claim:

Dr. Brian White, a now-retired LADWP biologist, was the first person to think of using shade balls for water quality. The idea came to him when he learned about the application of “bird balls” in ponds along airfield runways. The innovative, in-house solution has been used in LADWP’s open-air reservoirs since 2008 to block sunlight, prevent chemical reactions and curtail algae blooms. Currently in place at Upper Stone, Elysian and Ivanhoe reservoirs, the shade balls come with the added benefit of reducing evaporation off the reservoir surfaces by 85 to 90 percent.

In December 2015, Richard Harasick, LADWP’s director of water operations said in a statement:

“we are experiencing cost savings in the reduced use of chlorine because the shade balls have reduced the amount of algae growth requiring treatment.”

-- Source

This means that they are getting positive results since they implemented these into the reservoir system. So, the claim is most likely true.

They're round, so maybe the wind will "roll" them on the water, thus exposing thousandths of an inch of water to evaporation over the ball's surface area?

They are filled with water so that they don't blow away.

They're black, so they absorb heat and maybe transfer it to the water?

Yes, they do. But a special coating reduces this effect.

Made of black polyethylene, shade balls are filled with water so they don’t blow away. A coating resists ultraviolet light and degradation. -- Source

Do these things continue to be effective as the reservoir level rises/lowers?

Yes, if the reservoir level lowers. But if the reservoir level rises, the effectiveness decreases unless more balls are added.

How much water went in to creating 96 million of these things?

That's either classified or unknown. The manufacturers generally don't provide such information unless the customer asks for it.

Further reading:

L.A. Says Goodbye to ‘Shade Balls’

Shade Balls Are a Really Stupid Way to Conserve Water

Answer 3

The primary purpose of deploying shade balls on the surface of LA reservoirs is to protect water quality by preventing sunlight-triggered chemical reactions such as formation of bromate and disinfection by-products. The shade balls are also projected to prevent the annual loss to evaporation of about 300 million gallons of water from the reservoir's storage.

1. How much water went in to creating 96 million of these things?-Not yet accurately known since polyethylene is manufactured utilizing fracking which involves the uses of thousands of gallons of water. Also the balls used on the Los Angeles Reservoir weigh 40 grams and are filled with 200 grams of drinking water to give them weight.

300 million gallons of water saved. But how much water did it take to make those balls? How many other resources? The balls are four inches in diameter, and made from polyethylene plastic by XavierC. I could not find out how much they weigh, but Bloomberg Business says 96 million of them are being dumped into the reservoir. When you look at how polyethylene is made, it is essentially a solid fossil fuel, transformed using electricity and natural gas, which these days is made by fracking, using thousands of gallons of water. 1000 lbs of polyethylene = 188 lbs of oil and 827 lbs of natural gas and 159 kWh of electricity. Source: Do the "shade balls" actually save water? Maybe we need a life cycle analysis

2. Do these things continue to be effective as the reservoir level rises/lowers? Mostly effective according to an August 2016 check by Emily Guerin.

Emily Guerin of Southern California Public Radio recently checked in on everyone's favorite environmentally-friendly balls. She reports that although many of them have since been replaced by tarps, those that started last summer's craze—the 96 million bumping around in the LA Reservoir—are still going strong. "It has worked exactly as we planned it to work," Richard Harasick, director of water operations at LA Department of Water and Power, told Guerin. Source: LA's Shade Balls Are Still (Mostly) Going Strong

3. They're black, so they absorb heat and maybe transfer it to the water? No, the air in the shade balls prevents any heat transfer to the water according to the Los Angeles Department of Water and Power (LADWP).

We have found no significant or abnormal heat effects on the water. It is our observation that although the top surface of the shade balls absorb heat, the heat is not well conducted (plastic is a poor conductor) down to the water surface and the air. Rather, the shade balls act as a 4-inch insulation blanket since the 98 million balls cover the surface of the Los Angeles Reservoir. The reservoir itself, since it is such a deep pool of relatively cool water, helps to keep itself thermally stable at the surface.

As for the issue of thermal heating and bacteria, LADWP’s daily water quality monitoring and maintenance operations have found neither abnormal thermal effects nor bacterial breeding in the reservoirs as a result of the use of shade balls. The "Carbon Black" is a UV stabilizing agent which allows the balls at least 10 years of useful life. The black balls have been approved for contact with drinking water. According to the National Sanitation Foundation which has tested and certified the balls for contact with drinking water, the carbon black does indeed make the plastic more thermally, structurally, and chemically stable and resistant to UV degradation. Though the top surface of the shade balls absorb heat, the air in the shade balls act as a four-inch insulation blanket, thereby preventing any heat transfer to the water. Furthermore, the reservoir’s size and depth and flow-thru operations are able to keep the water cool. In fact, our staff has verified that the temperature of the water flowing out of LA Reservoir is half a degree cooler than the water that goes into it after filtration and UV disinfection. Source: LADWP news Factcheck

4. They're round, so maybe the wind will "roll" them on the water, thus exposing thousandths of an inch of water to evaporation over the ball's surface area? The shade balls are projected to contribute to saving 90 percent of water in the LA reservoir from evaporation . The rolling effects on the partially water filled shade balls are minimized by the weighing down which helps to counteract the wind force that tends to push the shade balls and expose the surface to sunlight.

The balls used on the Los Angeles Reservoir weigh 40 grams and are filled with 200 grams of drinking water to give them weight so they are not blown away by wind gusts, as the reservoir is located in a high gust area. Shade balls in place at other LA reservoirs - Elysian, Ivanhoe and Upper Stone Canyon - are hollow and not filled with water. Shade balls contribute to reducing the effects of evaporation by reducing the water surface area exposed to the sun, and by reducing the flow of wind above the water surface. It is estimated that up to 90 percent of water that would be lost due to evaporation could be saved when the reservoir is fully covered with shade balls. Shade balls at the Los Angeles Reservoir are partially water-filled to weigh them down to counteract the force of the winds that tends to push aside the shade balls and expose the surface to sunlight. Source: Shade Balls Frequently Asked Questions