The rather unsuccessful experiment by Minister for Cooperation Sellur K. Raju and officials using thermocol to prevent water evaporation from the Vaigai Dam has been ridiculed and panned by critics but studies show the concept has worked but only on a smaller area.
At least two papers on the topic show that thermocol is seen as a good agent to prevent evaporation, although it can be done only on a small scale, for example in a pond.
A paper on “Evaporation Control in Reservoirs” compiled by the Central Water Commission (CWC) Basin Planning and Management Organisation in 2006, looked at various means to reduce evaporation.
Quoting experiments done by the Department of Soil and Water Conservation Engineering, College of Technology and Agriculture Engineering, Rajasthan Agriculture University, the report said that thermocol was found to be the second best “evaporetardant” after mustard oil. The experiments were carried out using vegetable oils, wax, wheat husk, paddy husk, wooden blocks, saw dust and thermocol boards.
A conference paper by Neha Chaudhari and N.D. Chaudhari in 2015 on “Use of thermocol sheet as floating cover to reduce evaporation loss in farm pond,” said it was found that an average of 32% water could be saved using thermocol in a pond and used for irrigation.
Cost-effective
They experimented with the use of thermocol in a small pond in Devargaon Village in Nashik district. The cost of spreading thermocol over 75% area of the pond was ₹22,500, including the cost of transportation. The remaining area was left open to allow entry of air into the pond.
The paper says during the period of study, there was a thunderstorm that led to breakage of the thermocol sheets, but it was still effective later in reducing evaporation.
The report by the CWC too found thermocol to be effective in reducing evaporation, but its use in a large area could not be ascertained. “Thermocol board has been found to be more effective than straw, dust and wooden blocks. However, mass scale use of these materials is not recommended till results providing their economic and utility are available,” the report said quoting the various experiments.
