1) Measuring instrument 
A lysimeter is a measuring device which can be used to measure the amount of actual evapotranspiration which is released by plants, usually crops or trees. By recording the amount of precipitation that an area receives and the amount lost through the soil, the amount of water lost to evapotranspiration can be calculated. Lysimeters are of two type...
instrument for measuring percolation of water through soil
Laboratory column of selected representative soil or a protected monolith of undisturbed field soil with which it is possible to sample and monitor the movement of water and substances.
• (n.) An instrument for measuring the water that percolates through a certain depth of soil.
(from the article `hydrologic sciences`) The only reliable way of measuring actual evapotranspiration is to use large containers (sometimes on the order of several metres across) called ...
Laboratory column of selected representative soil or a protected monolith of undisturbed field soil with facilities for sampling and monitoring the movement of water and chemicals.
Ly·sim'e·ter (li*sĭm'e*tẽr) noun [ Greek 
Meteorological instrument used to measure potential and actual evapotranspiration.
an instrument for determining the amount of water-soluble matter in soil.