This document describes how to organize, set up, and collect the measurements of water table depth at ICOS ecosystem stations. The document is structured in four different sections with the aim to facilitate the use and application: - Measurements: in this section the sensors and material needed, the setup and methods to correctly collect the data and info are described. It includes sub-sections on sensor characteristics, practical indication for the setup/collection, info on the sampling design and guidelines for the installation/sampling also with respect to other sensors/measurements. - Maintenance: in this section the maintenance and calibration guidelines are described. - Submission: it is the section related to the data preparation and submission to the ETC. It includes the list of all the parameters, the correct formatting and the way to submit them to the database. - Processing: this section is for internal use of the ETC and describes the processing applied to the single variable/info submitted. It is important to remind that the exact application of the protocol at station level must be also discussed with ETC in order to reach agreed solutions for specific cases. If a specific part is relevant only for a specific ecosystem or station Class this is also reported in the document.