Evaporation Reduction: Summary of Long‐term Tank Studies

A review of evaporation reduction studies indicated that shades suspended above a water surface and floating covers on a water surface gave best results. Of the two, floating covers were most practical. Field tests using floating covers of foamed wax blocks, continuous wax, and foamed rubber reduced evaporation losses 36%–84% over an 8 yr period. Based on the amount of the water saved and the cost of materials used, the continuous wax covers provided the lowest cost water at $0.08 to $0.13/1,000 L/yr, followed by foamed rubber and foamed wax blocks at $0.17 and $0.18 per 1,000 L/yr, respectively. However, evaporation reduction efficiency of the continuous wax covers began to decrease after a few years of exposure, while the foamed rubber and foamed wax blocks showed no signs of deterioration. Long‐term durability, efficiency, and climatic range of usability should be considered along with costs when determining the most practical cover to use.