Evaluation of Evapo-Retardants and their Interrelationship with respect to Temperature and Wind Velocity

Farm ponds are constructed on massive scale in the state of Maharashtra for rain water harvesting at individual farm level. However it has been observed that most of the storage water is lost through evaporation from the ponds. Hence, there is an urgent need to focus on reduction of evaporation losses from the farm pond. About 20% area of the country falls under rain scarcity and drought area wherein there is an urgent need to control evaporation losses from water bodies like farm pond, village ponds, and lakes. A study was conducted with different evaporation retardants for reducing the loss of water through evaporation from small water bodies and their inter-relationship with temperature and wind velocity. Among all the treatments, the treatment T₆i.e. application of cetyl alcohol @ 15 mg/sq. m. at an interval of 5 days is found to be significantly superior over all other treatments and at par with treatment T₅i.e. application of cetyl alcohol @ 10 mg/sq. m. after every 5 days. In application of neem and vegetable oils, the evaporation rate was reduced up to the tune of 20–27%. However application of cetyl alcohol with various rate and duration were found to be effective in reducing evaporation rate in the tune of 54 to 66%. Considering the water availability for entire four months period after monsoon in the farm pond, the cost of application of cetyl alcohol is very less as compared to neem and vegetable oils. The co-relation of average weekly maximum temperature and average weekly wind velocity Vs. average weekly evaporation rate showed linear relationship. During monsoon and winter season there was no significant effect of increase in maximum temperature (up to 35°C) and wind velocity (up to 5 km/hr) with increase in evaporation rate. However during the period of summer, there was a significant impact of increase in maximum temperature (above 35°C) or wind velocity (above 6 km/hr) on increase in evaporation rate.