Measurement of Evapotranspiration Using Lysimeter

Abstract

Measurement Of Evapotranspiration Using Lysimeter The term lysimeter means differential measuring instrument and may be taken, in general, to apply to all instruments which measure weight changes, especially weight reduction due to evapotranspiration in a particular vo’lume of soil with or without accompanying vegetation. There are two main types of lysimeter in use: the drainage and the weighing types. In the first case, potential evaporation is obtained as the difference between added and drained water quantity. In the second case, changes in the total weight of the soil sample are measured, whereby the real evapotranspiration during as short a time as ten minutes can be estimated. There are two types i.e. the mechanical and the hydraulic weighing lysimeter.

Conclusion

A new dynamic weighing lysimeter is described. In principle, the dynamic lysimeter consists of a balance arm with a movable counterweight that continuously seeks a point of equilibrium by small movements. The times taken by these movements are read off as pulses and fed automatically into a data logger. The sensitivity of the lysimeter was varied between 0.04 g per pulse to 0.56 g per pulse depending on the mass of the movable counterweight. Contemporary meteorological measurements and lysimeter measurements are described. These were made at the Ecological Forest Research Station at Vindeln, with lichens and heather dominant in the ground vegetation.