“…Progress in the use of environmental tracers in hydrology significantly enhanced understanding of hydrological processes at hillslope and catchment scale. Specifically, studies based on isotopic (stable water isotopes, e.g., Dincer et al, 1970) and geochemical (major cations and anions, e.g., Pinder and Jones, 1969) tracers revealed a substantial role of the subsurface flow contribution to runoff events, which partly contradicted the traditional concept of the runoff formation. Typically, groundwater mixing and residence times are studied by isotopic tracers (e.g., Maloszewski and Zuber, 1996;McGuire and McDonnell, 2006).…”