Seasonal signals of stable isotopes in precipitation combined with measurements of soil water content have been used for a quantitative estimation of groundwater recharge rates. This study investigates the applicability of the piston flow principle and the peak shift displacement method for assessing recharge in a humid Nordic region located in Quebec in Canada to estimate groundwater recharge rates. Two different sites in the same unconfined aquifer were tested using measurements of soil water isotopes 18O/2H and of volumetric pore water content in core samples (2.45 m for one site and 4.15 m for the other) obtained along the vadose zone down to the groundwater table at the two sites. The end of snowmelt, fingerprinted by the isotopes, was identified in the pore water of the sediment profiles. The peak shift method was observed to be accurate in certain specific conditions inherent to the soil properties of the investigated sites, namely, when the soil properties are homogenous. Peak shift displacement and piston flow principle did not allow the accurate estimation of recharge in heterogenous environments, nor when the topography causes runoff/runon. At one of the two sites, recharge from the snowmelt could not be estimated because of heterogeneity in the lower part of the vadose zone. At this same site, however, the later post-snowmelt recharge could be estimated because the upper part of the vadose zone was homogeneous. At the other of the two sites, runoff/runon phenomena prevented the accurate calculation of infiltration and thus recharge. These two different site effects, heterogeneity in the first site and runoff/runon in the second site, were identified as being limiting factors for an accurate assessment of recharge. This study recommends the use of the peak shift method for humid Nordic regions characterized by homogeneous and thick vadose zones with limited site effects.