The Lower Grand River watershed (2000 km2) in Ontario’s Niagara Peninsula, a rural area that includes two First Nations reserves, relies heavily on groundwater for its water supply (about 80% of the population). The watershed largely hosts low-potential aquifers, as bedrock in the southern half consists of Salina Group evaporites-mudstones and the overlying Quaternary sediments are mostly fine-grained glacial lake deposits. In this context, domestic wells typically get water from the first few meters of fractured rock. Groundwater often contains various levels of NO3-, SO42-, Na+, Cl-, CH4, and H2S, potentially linked to the geological context, long history of oil and gas production, road deicing, and agriculture. Hence, there is a need for better characterization of lithology, hydrodynamics and groundwater quality to identify contaminant sources and support efficient and sustainable water management. Fieldwork last fall focused on drilling, borehole and geophysical logging and hydraulic testing of six monitoring wells, along with core and groundwater sampling. The wells are 15 to 125 m deep and were completed in bedrock (2), in sand (1), or at the sediment/bedrock interface (3). Fieldwork also included water temperature and level monitoring, and flow estimation in two streams. Two parallel studies being conducted as part of this project are 1) landscape and environmental changes over the past few decades using interviews with members of First Nations communities to better understand the region's transformation and 2) the origin of anomalous isotopic (δ34S) values of dissolved sulfate to better understand potential connections between shallow and deep units.