Evaporation rates from different pans under humid tropical conditions

Abstract

Under humid tropical conditions, the relative evaporation .rates from Class A open pan, G.G.I. 3000 and Colorado sunken pans were studied.. The recorded evaporation values were compared with evaporation estimated with a modified Penman equation. The Inter relationship between evaporation values and the influence of weather parameters on evaporation were also studied using statistical correlations.

About 88-93 per cent of insolation was absorbed from the pan surfaces for evaporation. The seasonal variation of evaporation was between 4 and 10. mm/day and the variation In evaporation due to type of pan used was up to 3 mm/day. The estimated evaporation values were within +-2.0 mm/day from the measured values. The evaporation values from the sunken pans were higher than from Class A by 1-3 mm/day and they were also closely correlated. The aerodynamic parameters were closely correlated with evaporation from Class A than from the sunken pans. The high soil thermal regime the area during October to May has increased the evaporation from the sunken pans.