Résumé - Abstract
Abandoned mine sites such as the Lorraine site in the Témiscamingue region can be a source of contamination of the environment if the acid mine drainage (AMD) they generate is not controlled with an appropriate reclamation method in the long term. In 1999, the Lorraine site was reclaimed with a cover with capillary barrier effects (CCBE) to limit the oxygen diffusion to the reactive mine wastes and the AMD generation.
The CCBE efficiently limits DMA production when the degree of water saturation (Sr) is maintained to a value greater than 85% in one of the layers, the moisture retaining layer (MRL). Yet, forest succession at Lorraine could reduce the water content of the MRL by root absorption and negatively affect the overall performance of the CCBE. The objective of this study is to model the effects of forest vegetation on the CCBE performance taking into account climate change (CC).
A 1-D conceptual model validated with field measurements was used from a previous study. The above and below-ground vegetation was characterized at the Lorraine site. Then volumetric water content, suction and Sr dynamics were modelled using the SEEP/W® 2021 software (GEO-SLOPE International Ltd.) under different vegetation scenarios under present and future climate.
Numerical simulations predicted an average Sr value along the growing season of 94% for present vegetation scenarios and of 68% for future scenarios. This sensitive decrease of Sr is partly due to higher water losses through transpiration in the MRL due to the higher leaf area index associated to increasing dominance of broadleaved species on coniferous species by 2100 under CC. Therefore, new forest species colonizing the Lorraine site are likely to significantly affect the long-term performance of the CCBE.