Snowmelt contributes a significant fraction of groundwater recharge in snow‐dominated regions, making its accurate quantification crucial for sustainable water resources management. While several components of the hydrological cycle can be measured directly, catchment‐scale recharge can only be quantified indirectly. Stable water isotopes are often used as tracers to estimate snowmelt recharge, even though estimates based on stable water isotopes are biased due to the large variations of δ²H and δ¹⁸O in snow and the difficulty to measure snowmelt directly. To overcome this gap, a new tracer method based on on‐site measurements of dissolved He, ⁴⁰Ar, ⁸⁴Kr, N₂, O₂, and CO₂ is presented. The new method was developed alongside classical tracer methods (stable water isotopes, ²²²Rn, ³H/³He) in a highly instrumented boreal catchment. By revealing (noble gas) recharge temperatures and excess air, dissolved gases allow (i) the contribution of snowmelt to recharge, (ii) the temporal recharge dynamics, and (iii) the primary recharge pathways to be identified. In contrast to stable water isotopes, which produced highly inconsistent snowmelt recharge estimates for the experimental catchment, dissolved gases produced consistent estimates even when the temperature of snowmelt during recharge was not precisely known. As dissolved gases are not controlled by the same processes as stable water isotopes, they are not prone to the same biases and represent a highly complementary tracer method for the quantification of snowmelt recharge dynamics in snow‐dominated regions. Furthermore, an observed systematic depletion of N₂ in groundwater provides new evidence for the pathways of biological N‐fixation in boreal forest soils.

Lettuce is an important crop in Canada, mainly grown in South West Quebec muck soils. Lettuce is sensitive to water stress during periods of high...

Summary: Maple trees repair cold‐induced embolism by generating positive stem pressure during their leafless state, altering sap transport in ways that remain poorly understood. This xylem pressure also drives sap exudation, enabling maple sap harvest for syrup production. This study investigates water source dynamics in leafless maples in early spring and its impact on sap yields. We used heavy water (D ₂ O) as a tracer, injected into the soil for root uptake or directly into the stem at various heights of 55 tapped maple trees. Sap isotopic composition was monitored over time and analyzed in relation to weather, sap volume, and sugar content. Our findings show that maple trees absorb soil water gradually in early spring, even when leafless and still under snow cover, with limited sap transport and significant water mixing within the stem. Root‐derived water first appeared around the sixth freeze–thaw event, marking a key rehydration phase coinciding with peak sap yields. Optimal daily maple sap yields also depended on cold nights to enhance sugar concentration, followed by extended thaws at moderate temperatures (3–5°C) to increase sap volume. These results highlight the combined influence of xylem physiology and weather conditions on spring stem rehydration and maple sap yields.

Temperature-index (TI) models are commonly used to simulate the volume and occurrence of meltwater in snow-fed catchments. TI models have varying levels of complexity but are all based on air temperature observations. The quality and availability of data that drive these models affect their predictive ability, particularly given that they are frequently applied in remote environments. This study investigates the performance of non-calibrated TI models in simulating the subcanopy snow water equivalent (SWE) of a small watershed located in Eastern Canada, for which some distinctive observations were collected. Among three relatively simple TI algorithms, the model that performed the best was selected based on the average percent bias (Pbias of 24%) and root mean square error (RMSE of 100 mm w.e.), and was designated as the base TI model. Then, a series of supplemental tests were conducted in order to quantify the performance gain that resulted from including the following inputs/processes to the base TI model: subcanopy incoming radiation, canopy interception, snow surface temperature, sublimation, and cold content. As a final test, all the above modifications were performed simultaneously. Our results reveal that, with the exception of snow sublimation (Pbias of 5.4%) and snow surface temperature, the variables mentioned above were unable to improve TI models within our sites. It is therefore worth exploring other feasible alternatives to existing TI models in complex forested environments.