Water Cycles - Hydrogeology: Objectives, Methods, Applications - page 29

f) Experimental methods
AET can be experimentally determined with the help of a lysimeter, a
container holding soil, with or without vegetation cover, for which the
amount of runoff and infi ltration are measured and compared to the amount
of infl ow due to precipitation. These measurements can be made by weight
or by collecting the infi ltrated water.
Figure 10 Actual evapotranspiration measured on plots in the Netherlands (from Lambert,
1996).
g) Direct measurements
Remote sensing allows the creation, based on thermal infrared satellite
images, of surface temperature and actual evapotranspiration maps (Vidal,
1991).
At Europe scale, one considers that 60% of rainfall water returns back
to the atmosphere due to evapotranspiration (Figure 11).