Introduction

Evaporation of water is a major factor in hydrologic systems. In general, an understanding of hydrologic systems requires an understanding of evaporation. The most economical means of providing additional usable water supplies is the conservation of water contained in existing storage facilities. One approach to attempting to conserve water stored in reservoirs has been the application of a monolayer to the water surface to reduce evaporation. Evaporation from soils is an important factor in managing both irrigated and dryland farming operations. The evaporation of water from vegetated surfaces is one of the less understood aspects of the hydrologic cycle. Measurement of evapotranspiration is necessary to obtain engineering data on the time pattern of water use by crops and for irrigation criteria. Retardation of water fog evaporation could be used in diverse applications including blanketing of frost-threatened crops with a radiative barrier and military optical screening.