<p>An evaporation events counter apparatus is described, which is adjusted to count as small as possible evaporation events, less than 2&#xa0;mm. The water lost during an evaporation event is returned to reset the apparatus for the next one. During this process, a counter records each event. The number of recorded events over a specific period (e.g., 1&#xa0;week), along with the evaporation in millimeters per event, provides the total evaporation for the time selected. The purpose of the apparatus is to collect water evaporation data for a hydraulic evapotranspiration multisensor irrigation system. Said data will be compared with that from a Class A evaporation pan to determine the corrective factor to be applied when setting multisensor to irrigate a particular crop, following the generally accepted evapotranspiration formulas. For this reason, the proposed apparatus should be made identical to the controlling part of multisensor, the irrigation frequency of which depends on the evaporation rate in its evaporation pan, which is identical as that of the evaporation events counter apparatus.</p>