The combined use of shade-cloth covers and monolayers to prevent evaporation in irrigation reservoirs

Abstract

One of the most efficient techniques to prevent evaporation is suspended shade covers, reported to reduce evaporation up to 85%, although at considerable cost. Another option is the application of a chemical monolayer which creates a film over the water surface that can reduce evaporation, but performance of these is limited by environmental exposure. In this study, a detailed trial was conducted in southern Queensland (Australia) to assess the benefits of the combined use of monolayers and shade-cloth covers. Three experimental tanks were monitored to measure evaporation, water temperature profile and the meteorological factors driving evaporative demand. Tanks 1 and 2 were covered with a black polyethylene mesh; a monolayer was added to Tank 2; and Tank 3 was uncovered and used as a control. The comparison of Tanks 1 and 2 with Tank 3 provided the evaporation reduction factors. The differences between the reduction factors of Tanks 2 and 3 allowed assessment of the performance of the combination of the two evaporation-suppression methods.