Use of Bellani plate evaporimeters for estimation of pet

Abstract

There is a need to understand better water budgets in hilly terrain and the potential evapotranspiration (PET) component as related to topography. Black and white Bellani plate evaporimeters were evaluated for suitability as a tool for obtaining weekly estimates of PET in remote areas with steep slopes. Polypropylene check valves were substituted for the Livingstone-Thone check valves and were superior for restricting water uptake during periods of extended rainfall. Assemblies were mounted in 500-ml Erlenmeyer flasks with screw-top closures which provided an adequate reservoir for weekly measurement and could be capped for transport to the laboratory for weighing. Black plate evaporation was more highly correlated with climate parameters than white plate evaporation, or USWB class A pan evaporation. Bellani plate evaporation was most highly correlated with an advective term calculated by multiplying the average vapor pressure deficit at 15.00 h by daily wind. Solar radiation was slightly less correlated to evaporation than the advection term. The two terms together gave a very good prediction of weekly evaporation. Black plate evaporimeters appear to be useful tools for estimating PET as a function of topography where rough terrain prohibits the use of USWB class A pans or lysimeters.