Researchers study groundwater impacts on beaches

Does groundwater impact water quality at your beach?

This question puzzles many communities trying to determine if septic systems and leaky sewers contribute to the algae that washes up along the shoreline or if they increase the number of beach postings caused by high E. coli levels.

Researchers at Western University, University of Waterloo and Environment Canada’s National Water Research Institute are pooling their expertise to tackle this question in a three-year project funded by the National Sciences and Engineering Research Council of Canada. Evaluating the impact of groundwater to beach water quality in the Great Lakes, and how to manage it, is a complex undertaking.

It requires knowledge of not only specific groundwater pollution sources (such as septic systems, leaky sewers, or agriculture) but also knowledge of the basic processes (physical water flow, chemical reactions and bacterial processes) underlying the movement of contaminants in the groundwater and their discharge to a lake.

Even if groundwater 100 metres from the shoreline is contaminated with high levels of E. coli and nutrients (nitrogen and phosphorus), that does not necessarily mean that these contaminants will discharge from the groundwater to a lake. Groundwater contaminants can undergo important reactions and potentially be removed by natural reactive processes before they are transported into a lake.

Alternatively, as is the case for E. coli, contaminants can also accumulate in the beach sand and groundwater at the shoreline waiting for a storm event or sand erosion to transport them to the shallow lake waters.

For this project, detailed field studies of the groundwater flows and the nutrient and bacterial processes will be conducted on several beaches around Lake Huron, Lake Ontario and South Georgian Bay. Field sites will cover a range of beaches, from pristine to more degraded beaches. The data collected will be combined with laboratory investigations, advanced computer modeling and the development of simple tools to assist beach managers and municipalities when they make decisions regarding the impacts of groundwater as a source of pollution along their shoreline. For more information regarding this project, please contact Dr. Clare Robinson at Western University (crobinson@eng.uwo.ca).