Reducing Pond Evaporation with Perlite Ore

Floating solid and granular materials appear to provide a practical means of reducing evaporation losses from open water surfaces. The increased efficiency of these materials over monomolecular films is due to their ability to reflect a greater portion of the incoming radiation. Perlite ore reduced pond evaporation 19%, over a 9-month period, for $0.36/1,000 l, which compares with previous studies conducted on small tanks. Temperatures were reduced 1D C to 3D C at the surface and 3D to 5D at the 91-cm depth. Wind caused the perlite to compact and windrow; however, the perlite redistributed when the wind receded. A complete perlite cover did not affect fish growth significantly during the cool months, but was detrimental during the hot summer season. Oxygen content of the covered pond was also reduced during the hot season.