| Buried esker systems are a major source of potable water in Eastern Ontario. Ever since the Clean Water Act was passed in 2006, efforts have been placed on understanding aquifers and characterizing watersheds in order to protect source water. This thesis focuses on one esker, extending from Vars to Winchester in the South Nation River watershed, which provides municipal water for seven villages -- an estimated population of 17,000. The esker complex is conceptualized as a 50-km long deposit of glaciofluvial outwash high-permeability material that is generally surrounded by fine, low permeability materials, except in a number of locations where the esker outcrops at ground surface. The complex recharges at its northern- and southern-most areas, which correspond to topographic highs it discharges in a topographically low area at its center near the village of Embrun. Regional stratigraphy was simplified for modeling purposes and brought down to six hydrostratigraphic units, two of which represent the esker: a coarser core, composed of a mixture of coarse sand and gravel, and sandy fan deposits.A three-dimensional hydrogeological model was developed using a finite element groundwater flow system, FEFLOW. Recharge and hydraulic conductivities were adjusted during calibration. Calibration was assessed using the mean error of residuals, standard deviation of residuals and normalized Root Mean Square calculations correlation was estimated using the determination coefficient and Pearson's coefficient. Results favour the conceptualization of the esker as a continuous, heterogeneous deposit comprising a gravelly core and sandy fans (ME=-4.33m, RMS=5.67m, n=18 wells in close proximity of esker) however, mean residuals are not significantly different when testing the discontinuous and homogeneous esker hypotheses. Sensitivity analyses testing the model's response to recharge and pumping showed that the system is relatively resilient however, our better judgement tells us that this is an artefact due to boundary conditions and not an adequate prediction of what may happen. Nevertheless, we hope this model will be a facilitating tool for understanding, managing and protecting the aquifer's resource. |
