Factors Affecting the Use of Evaporation Pan Data in East Africa

Abstract

The Most Extensive Set Of Data On Evaporation In East Africa Is from Evaporation Pans And It Is Necessary Therefore To Consider How Best To Use this Information. In Addition There Are Some Supplementary Estimates of Evaporation from Meteorogical Observations, By the Penman Method, Which Can He Used In interpreting The Pan Data. A Casual Glance at the Pan Data Shows That It Would Certainly Be Unwise To Use the Evaporation Figures Directly and Unmodified. It Is Unfortunate That The Interpretation Of Pan Data Into Meaningful terms Is Not At All Straightforward, And It Must Be Appreciated That The Data Available For A Specific Pan Give The Amounts Of Water Lost By That Particular Pan Lin That Particular Environment. The Results Are Influenced By Pan Colour, Size, Shape And Exposure And The State Of The Environment Over Large Distances Compared With The Size Of A Meteorological Enclosure. The Pan Data Reviewed By Mcculloch (1961) Showed A Wide Variety Of Effects Of Exposure And Environment But These Were Not Discussed In Detail And It, Is Useful To Consider The Basic Processes Involved Before Examining The Performance Of Specific Types Of Evaporation Pan.