A combined water and energy balance study at Katherine, Northern Territory

A study is made of the "typical" monthly evaporation of a growing crop at Katherine, Northern Territory, based on a combined water and energy balance approach. The values obtained differ significantly during the "dry" season and the early part of the "wet" season from an earlier estimate based on tank evaporation, when solar radiation data were not available. The consistent nature of the analysis together with the numerous cross-checks available from the combined approach, suggests that satisfactory estimates of wafer usage can be made from physical arguments alone, thus relegating the detail of plant behaviour to a secondary role. This follows mainly from the sharp division into two major seasons. The validity of this and similar studies would be considerably advanced if measurements of net radiation were made directly, rather than relying on estimated values of radiation components not recorded by a solarimeter.