refilled each time a measurement is made, with a calibrated
graduation.
For continous recording, mechanical water level recorders can
be connected to the evaporation pan, or water level gauges
with an electrical output can be used with appropriate
recording devices.
For special applications, recording evaporation balances
(evaporation surface 250 cm ), or other devices using porous
ceramic discs or spheres have been designed (Evaporimeter
"Bellani","Livingstone").
2.6.23 Instruments to measure potential or actual evapotranspiration.
Lysimeters are field tanks of varying types and dimensions
containing natural soil and vegetation. Provisions are made
which allow a detailed assessment of the water budget inside
the tank (by measurements of the precipitation and drainage,
weighing the entire tank, soil moisture measurements inside
the tank.
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