As a tracer in hydrology, tritium can be used for different purposes, such as groundwater dating; hydraulic measurements; determination of the distribution of residence times in large bodies of water and in the atmosphere; water balance measurements, and in studies on the dispersion of contaminants. Time series of tritium concentration in rain water and at specific observation points of the hydrological system are used to obtain lumped-parameter models capable of describing the distribution of residence times of the water in the hydrological cycle compartments. This paper presents a description of theoretical and practical aspects involved in the application of these techniques, the state-of-the-art of scientific studies involving the application of environmental tritium in groundwater and watersheds, as well as the new on-going trends in this area.
