When Groundwater Sneaks to the Sea: Lessons from a Nova Scotia Harbour

Takeaway: In this Nova Scotia harbour, most groundwater reached the sea by first feeding streams, not by quietly leaking straight through the harbour floor.Coastal water problems often look like they begin at the shoreline: a beach closes, shellfish harvests pause, or a harbour turns unexpectedly risky after rain. But the water carrying nutrients or bacteria may have started underground, moving through soil and rock long before anyone sees it. In this episode, we visit Mabou Harbour on Cape Breton Island, Nova Scotia, where researchers asked a practical question with big stakes for coastal communities: does groundwater reach the sea mostly by seeping directly through the harbour bottom, or by feeding streams that then empty into the harbour? The answer matters for monitoring pollution, protecting aquaculture, and understanding how glacial landscapes route freshwater to the coast. The study found that in this till-dominated watershed, direct submarine groundwater discharge was a small part of the full watershed budget: about 3.9% of groundwater discharge, compared with 96.1% delivered as stream baseflow. But the groundwater that does seep directly into the harbour tends to come from nearby land and travel along shorter paths, which can leave less time for natural filtering before it reaches coastal water. This episode uses AI-generated voices. Citation: Craddock, R.D., Kennedy, G.W., Jamieson, R.C., Keizer, J., Mohammed, A.A., & Kurylyk, B.L. (2022). Assessment of groundwater discharge pathways in a till-dominated coastal aquifer. Journal of Hydrology: Regional Studies, 44, 101205. https://doi.org/10.1016/j.ejrh.2022.101205