Environmental seismology” is a rapidly growing field that aims to provide new observables and proxies to characterize and monitor earth surface processes, especially when subject to anthropogenic or climate forcing. It is mostly based on the recording and analysis of ambient ground vibrations (sometimes referred as ”seismic noise”) induced by such human and environmental sources, which, in turn, can also be used to image the elastic properties of the medium. Since the end of 2020, we have initiated a project named SiPaZoc (passive seismology for critical zone studies) to evaluate the ability of different passive seismic approaches to characterize the critical zone, the evolution of its water resource, and the dynamic of surface transport of the Strengbach watershed (Haut-Rhin, France), a small headwater catchment hosting the OHGE French national observatory. The project mostly consists of a series of deployments of miniaturized seismometers (”nodes”) borrowed from the DENSAR park managed by Ecole et Observatoire des Sciences de la Terre -A network of 99 nodes, distributed across the entire watershed along a homogeneous grid and three denser profiles. This network, deployed for ̃3 weeks in Nov-Dec. 2020, aimed to record ambient seismic noise, characterize the main local sources generating this noise, and implement cross-correlation approaches between pairs of sensors to build a 3D velocity (Vs) model of the first ̃50 meters at depth of the whole basin. - A network of 6 nodes located in the central part of the watershed and operating continu- ously for several months (measurements started in Feb. 2021). This network aims to take advantage of the pervasive aspect of the ambient seismic noise to determine, by interferometric approaches on ambient noise cross-correlations, small temporal variations of seismic velocities induced by variations of the water content in the subsurface