The Advantages of Using High Resolution Datasets in Water Resources Investigation Studies: An Example in a Complex End Moraine to Wetland Setting

ABSTRACT: The heterogeneous nature of ice marginal settings and the dynamics of groundwater flow in multilayered systems make these spatially complex environments difficult to characterize, requiring detailed information to understand their role from a water resources perspective. The study area in Guelph, Ontario is situated in a complex end moraine setting overlying the Silurian dolostone aquifer with a new bedrock municipal supply well proposed adjacent to a sensitive wetland. The objective of this study is to determine the vertical hydraulic connectivity throughout the bedrock and overlying Quaternary sediments to determine 3D capture zones and sustainable pumping rates. Multiple high-resolution datasets were collected to characterize the subsurface geological and hydrogeological variability used to create a Conceptual Site Model (CSM) of the multilayered flow system. Logging of continuous cores and natural gamma at 4 locations oriented perpendicular to the trend of the moraine show a transition from end moraine front slope fans into mixed outwash plain and lacustrine depositional environments where a wetland is now located. Custom depth discrete G360 Multilevel Systems (MLS's) were installed in these boreholes and instrumented with transducers, providing depth-discrete vertical profiles of hydraulic head and transient responses to recharge and bedrock aquifer pumping used to delineate Hydrogeologic Units (HGU's) and lateral continuity of low K beds. The vertical head profiles at a point in time along with the transient water level responses to natural and anthropogenic signals will be used to further refine the hydrogeologic unit occurrence and parameters across the study area. The groundwater flow system is dynamic in the study area due to multiple pumping locations with municipal and private wells for drinking water and industrial operations with a nearby gravel pit. The resolution of spatiotemporal data is unprecedented and provides insights on the multiple interactive hydraulic influences due to natural and anthropogenic influences. The ongoing monitoring will support decisions regarding municipal well capture zones and sustainable pumping rates to minimize impacts to shallow groundwater and wetland.