Suppressing evaporation from surface water reservoirs: A review

The availability of water for agriculture is declining due to competing demands from other sectors, mainly industry and human need. Water conservation and harvesting is the only solution to overcome the vagaries of monsoon in the Indian sub-continent. The precious blue water needs to be converted into green water without loosing through seepage and evaporation. Seepage is beneficial as it recharges groundwater. Evaporation although improves micro-climate, needs to be controlled. The review highlights various physical, chemical, biological or the combination of methods undertaken to control the evaporation in India. Monolayer like cetyl and stearyl alcohol alone, or in combination of both, reported to control evaporation up to 30 % and 57 %, respectively. Biological measures using agricultural waste are cost-effective and reported to reduce evaporation up to 60 % with palm fronds. Mechanical measures like foating type solar panels, though expensive, are useful with multiple benefits. Mechanical shields like suspended shade cloth, thermocol, styrofoam and foating wax studied by various researchers reportedly control evaporation ranging between 25 % and 70 per cent. Bubble plume technique indicated varied reduction in evaporation with depth of water storage structure from 15- 25 per cent. From the extensive review, it could be concluded that foating/fixed type solar panels, depending on the type of water body, are the most effective and may be subsidised to increase it’ adoption.