Groundwater recharge over the past 100 years: Regional spatiotemporal assessment and climate change impact over the Saguenay‐Lac‐Saint‐Jean region, Canada

Proper knowledge of potential groundwater recharge (PGR) and its spatiotemporal distribution are essential for sustainable groundwater management, especially within the context of climate change. Here, a robust GIS‐based water budget framework was developed to estimate PGR at a regional scale and map its spatial distribution. This framework is demonstrated over the Saguenay‐Lac‐Saint‐Jean region (13 200 km2) of Quebec (Canada). The PGR mapping process was based on a model incorporating water budget components. The vertical inflows (VI) include water amounts from rainfall and snowmelt, whereby the latter was assessed using HYDROTEL model. VI were combined with the maximum and minimum temperatures to estimate actual evapotranspiration (AET), while the surface runoff (RuS) was assessed using the curve number method. Field observations of annual variation in temperatures and the water budget components, over a period of 100 years (1910–2009), were used to provide a comprehensive overview of the effects of climate change on PGR. The last 10 years of the observation period (i.e., 2000–2009) indicate that 6% of the study area has PGR rates of 35%–50%. PGR rates of 20%–35% occur in 58% of the study area, while 36% have PGR of 5%–20%. The trend analysis of temperature time series reveals an average of 1.1 ± 0.6°C increase over 100 years. Also, an increase in the water budget components is observed. Despite the increasing trends of RuS and AET, PGR still showed an increasing trend with an average increase of 0.7 ± 0.4 mm/year over the past 100 years. This observation indicates that the increase in VI was enough to compensate for the increases in AET and RuS. This finding of an increasing PGR in the study area provides useful information for future studies focusing on predicting long‐term PGR evolution and for the development of efficient long‐term groundwater management strategies. This manuscript provides the first regional‐scale groundwater recharge map for the Saguenay‐Lac‐Saint‐Jean region of Quebec (Canada). This manuscript demonstrates a robust and pragmatic GIS‐based water budget framework for the evaluation of groundwater recharge at a regional scale. This manuscript provides a comprehensive overview of the effect of climate change on groundwater recharge from 100 years of field observations (1910–2009) for the Saguenay‐Lac‐Saint‐Jean region of Quebec (Canada).