Présentations Colloques

In this study, water isotopes, together with other tracers have been employed for understanding the interconnectivity between precipitation, surface runoff, groundwater recharge and discharge, and streamflow. The study has been carried out in Black Brook Watershed (14.5 km2 watershed area+ moderately cool temperate climate) and involved watershed-scale seasonal sampling complemented by intensive event-based sampling. The water isotopic signatures of all the samples were narrowly distributed along the regional metoric water line, however precipitation showed significantly larger range (-99‰40 mbg) showed slightly more negative isotopic signature when compared to shallower groundwater, potentially indicating mixing with ancient waters recharged under a different climate. Isotopic signature of precipitation showed no spatial variability at the watershed scale. Groundwater and stream had similar seasonal isotopic composition, showing that groundwater is the major contributor (~70%) to streamflow, which has been confirmed by hydrograph separation. Mixing models developed using additional tracers (e.g. NO3, Cl), yielded similar results with respect to water partitioning and groundwater recharge during the sampled events as well as throughout the year, showing that water isotopes are a powerful tool when used in combination with other methods.