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Abstract

Lake Papineau (13 km²) and its watershed (93 km²) are situated in the Kenauk Nature private reserve, midway between Ottawa and Montreal, Canada on the Canadian Shield. In partnership with Kenauk Nature, Nature Conservancy of Canada and Ouranos, this project assesses the resilience of the lake hydrosystem and its associated lake-edge wetlands under current and future climatic and anthropic pressures. To do so, the components of the lake water budget, notably the annual groundwater contribution (5-7% of inflows), were quantified under recent and historical conditions. Use of the Budyko theoretical framework in conjunction with the HydroBudget surface-water balance model verified the coherence of simulated runoff, recharge and actual evapotranspiration with the hydroclimatic context of southern Quebec. A MODFLOW model was subsequently developed to simulate the lake water budget and the lake stage, with the latter crucial for assessing the impact of future stage variations on lake-edge wetlands. In partnership with Ouranos, twelve future climate scenarios (RCP 4.5 and 8.5) were simulated with MODFLOW, indicating an approximately 15% and 20% annual increase in direct precipitation and evaporation, respectively, along with shorter and warmer winters as well as longer and dryer summers at the 2071-2100 horizon. These changing climatic conditions are expected to induce higher lake stages in winter (+10 cm) and lower stages during the spring freshet (-10 cm), while having negligible effect on summer stages. Groundwater inflow to Lake Papineau is expected to increase more moderately (+4.8%), in keeping with expected increases in groundwater recharge (+7.4%).