Présentations Colloques

Oral Presentation
Session 8.06: Verification of conceptual patterns and expected natural effects of regional groundwater flow by interpretation of relevant field observations
Judit Déri-takács
Quantification of the effects of topography-driven groundwater flow by coupling field observations and numerical models in Wood Buffalo National Park, Canada
Wood Buffalo National Park (WBNP) is Canada’s largest national park, approximately 45 000 km2 in areal extent. Due to its protected status and poor accessibility, the hydrogeology of the area has not been extensively studied. The need for a hydrogeological evaluation arose because of potential impacts due to increased recreational use and anticipated mining activities. In this study, observed field phenomena were coupled with numerically calculated flow fields to characterize the hydrogeological conditions in selected regions of WBNP.**The Park exhibits classic examples of surface phenomena thought to be associated with groundwater discharge, such as springs with variable and distinct chemical compositions, extended salt plains and or phreatophytic plant communities. Our working hypothesis is that groundwater flow in the Park is controlled by water-table relief and observed surface phenomena reflect the different orders and segments of groundwater flow systems. **Chemical analyses of surface waters and springs were used to determine the hydrochemical characteristics of WBNP (e.g., total dissolved solids, TDS) and to develop a hydrochemical facies classification in WBNP. The hydrochemical analyses revealed significant variability in TDS and hydrochemical facies, i.e. TDS ranging from less than 1,000 mg L to more than 300,000 mg L and hydrochemical facies including end-members of young Ca-HCO3-type to more evolved Na-Cl-type waters. Numerical models of groundwater flow were developed to quantify the flow field and to identify recharge and discharge areas in selected regions. Comparison of numerical simulations with field data indicated strong correlations between the modelled flow fields and the chemical character of surface water samples. For example, Ca-HCO3-type waters with low TDS correspond with discharge areas of local flow systems and Na-Cl-type waters with high TDS are found in discharge areas of regional systems. **The results suggest that differences in water chemical character are good indicators of different orders and segments of groundwater flow systems in WBNP and can, therefore, be considered manifestations of topography-driven groundwater flow.