My name is Mitja Janža, and I am researcher at the Geological Survey of Slovenia, specializing in hydrogeological modelling. Thanks to project WATSON and the Short Term Scientific Missions (STSM) program I had the opportunity of collaborating with Croatian Geological Survey (HGI) and working closely with colleagues Tamara Marković and Igor Karlović. Our research was focused on the collection and interpretation of water isotope data for the development of conceptual and numerical hydrological models to simulate the movement of water (and pollutants) on two selected study areas. Understanding and simulating the water cycle in the selected aquifer catchments is essential for planning protective measures and managing contaminated groundwater resources effectively. To enhance our sampling capabilities, we tested a prototype of an automatic rainfall sampler and explored potential enhancements of the device.