After thermocol, TN may move to plastic balls to save water, but at what cost?

Tamil Nadu’s officials, it appears, will not be bogged down by its disastrous thermocol experiment. With the state reeling from its worst drought in 140 years, officials have conceived another plan to conserve water following Friday’s failed attempt to float thermocol sheets to contain evaporation in Madurai’s Vaigai dam. Instead of thermocol sheets, the district administration may look at plastic ‘shade balls’ to save water.

In an interview to The Hindu, Madurai Collector K Veera Raghava Rao suggested that the district administration was considering releasing shade balls into the Vaigai dam to prevent evaporation loss, a method adopted by Los Angeles in the United States.

What are shade balls?

Measuring four-inches, these black plastic balls were first released into the Los Angeles Reservoir by the Los Angeles Department of Water and Power in 2008. Over a span of seven years, 96 million shade balls were released into the 175-acre reservoir at a cost of 34.5 million dollars.

LA’s Mayor in 2015 stated that the move would reduce evaporation besides protecting the water quality by preventing “sunlight-triggered chemical reactions” and curtail the formation of algae. The black plastic balls work by blocking the sun’s rays.  

Officials had proudly declared that the “cost-effective” measure that required minimum maintenance apart from the occasional rotation of the shade balls, would reduce evaporation by 85 to 90% or roughly nearly 300 million gallons every year.  

Unlike the thermocol experiment in Tamil Nadu, which failed owing to the strong winds, shade balls are made of black polyethylene and are filled with water preventing them from getting blown away, reported National Geographic.

Success or hype?

Although the video of the plastic balls being released into the reservoir went viral in 2015, many have questioned the success of the experiment. While Daily Mail quoted hydrologists to argue that the shade balls could increase bacteria in the water, there have also been accusations that the black spheres could release dangerous chemicals into the water.   

However, in hindsight, officials in LA admit shade balls were not a permanent solution. They have since been removed in most reservoirs in Los Angeles, replaced by floating covers, which offer more protection from sunlight and airborne contaminants, reports Governing. Owing to its size – measuring 175 acres – LA Reservoir remains the only site where shade balls continue to be used, with floating covers proving to be too costly.

In the case of Vaigai reservoir, which reportedly measures 12 hectares or about 30 acres, floating covers may be a more viable alternative. However, the question is does the state government have millions of dollars to spend on an idea that requires more research. And if Friday’s failed thermocol experiment is anything to go by, it’s the execution of the idea and not the idea itself that remains vital to its success.