Pollution, droughts, floods, ground-surface water connection, erosion processes are among the most structuring factors in catchments. Isotopes are used to trace water provenance, recharge processes, geochemical reactions, catchment transit times, to quantify flow paths and coupled ecohydrological processes. This session focuses on the application of traditional isotopes and new developed ones as proxies to determine the sources, dynamics and chemistry of water, to present new methods in tracer hydrology to improve models, to specify external influences (human activities) and global change (erosion, weathering rate, water transfer) with the goal of managing the quantity/quality of water in catchments in the frame of global change.