Spatially distributed recharge modelling with commonly available data - Application to the Centre-du-Québec region of southern Quebec (Canada)

English Abstract:

The estimation of mean groundwater recharge over a watershed is a relatively simple task when using a global water balance. However, such a simple recharge estimate often hides local variations of recharge that depend on geological, topographical or land use heterogeneity within the watershed. There is clearly a need to develop and use recharge models aimed at calculating spatially distributed recharge rates for regional scale hydrogeological studies. The objective of this work was to develop an approach to quantify spatially distributed recharge rates based on commonly available data. The HydroBilan model was developed to estimates surface infiltration by calculating a spatial water balance with a 500 m x 500 m grid resolution. The model uses the temporally variable runoff estimate from the Runoff Curve Number (RCN) method adapted for southern Quebec, as well as the daily vertical inflows generated by the Centre d'expertise hydrique du Québec and the daily air temperature. Slope, land use and soil type data are extracted from a database typical of those generally available. A limited number of parameters, including soil freezing, moisture conditions and percentage of water that effectively infiltrates daily into the soil, require calibration. The model was calibrated with a 21-year time series on a 1550 km² sub-watershed to minimize the error between calculated runoff, evapotranspiration and seasonal evolution of the infiltration. The calibration was performed to reproduce the total runoff/recharge ratios simulated with the MOHYSE hydrological model as well as those from base flow separation data. The calibrated parameters were then used on the Nicolet and the lower Saint-François watersheds in the Centre-du-Québec region of southern Quebec (Canada; 18 300 cells over 4500 km²). The model estimates an average recharge of 152 mm/year for the study area and a preferential recharge zone over the Appalachian Mountains and a low recharge zone over the sedimentary plains. The HydroBilan model reaches its full potential in the Appalachian Piedmont where it allows the identification of sparsely distributed recharge areas. Potential recharge, evapotranspiration and runoff respectively represent 14%, 42% and 44% of the total water budget.