Groundwater supplies drinking water for over 80% of residents in southern Ontario’s lower Grand River watershed (2000 km²), which includes two First Nations reserves. Persistent water insecurity in this region stems from poor water quality and low aquifer yield, exacerbated by agricultural intensification, urban expansion, and climate change -- which alter both recharge and discharge rates -- leading to a reduction in annual baseflow. Despite the importance of groundwater in this watershed, its interactions with surface water and recharge-discharge patterns in the region remain poorly characterized due to limited monitoring and fragmented datasets. High-resolution temperature and hydrometric data have been collected using iButtons, fibre-optic distributed temperature sensing, current profilers, pressure transducers, and surface water loggers. A drone-mounted thermal infrared survey is planned in February to expand discharge mapping. This work aims to identify groundwater recharge and discharge zones, quantify fluxes, and numerically simulate aquifer responses under various scenarios, including climate change. Field investigations have included core drilling, monitoring well installation, hydraulic testing, and advanced thermal sensing, complemented by geospatial and remote sensing analyses. A conceptual model will integrate existing and new datasets and will form the basis for the development of a 3D numerical coupled model (HydroGeoSphere). Novelty lies in combining: 1) emerging thermal sensing technologies, 2) the use of remote sensing to detect flux changes, and 3) advanced modeling to investigate hydrogeological processes, including groundwater-surface water interactions, notably between fine-grained surficial sediments and low-permeability bedrock which dominate the region of interest.