ABSTRACT
A lysimeter is a soil-filled container placed in a field on which vegetation can be grown. Evaporation or evapotranspiration can be directly determined, using a weighing lysimeter, as the loss in weight of the lysimeter with time. Lysimetry is the only method in which each of the quantities in the water balance is completely known. Over approximate time periods, there is a high correlation of pan evaporation to potential evapotranspiration even though the pan is a poor analog of a vegetation surface. The siting of the pan affects the measured pan evaporation greatly, therefore, calibration of an evaporation pan to a given locale is mandatory. There are, as in all measurement systems, limitations on the accuracy with which lysimeters measure water loss from the soil volume. Minimizable factors that affect the accuracy of lysimeters are wind and the ratio of the surface area to the depth of the lysimeter.
