Multi-dimensional water quality assessment of an urban drinking water source elucidated by high resolution underwater towed vehicle mapping

• UTV can identify upwelling groundwater vent sites in freshwater.
• UTV mapping provides high spatial resolution monitoring.
• UTV mapping identifies contaminant sources that would be missed using traditional methods.
• Inflow sources can be chemically differentiated between other sources and the risk assessed.
• Geological structures may guide the identification of the inflow sources.

Spatial surveys of Ramsey Lake, Sudbury, Ontario water quality were conducted using an innovative underwater towed vehicle (UTV) equipped with a multi-parameter probe providing real-time water quality data. The UTV revealed underwater vent sites through high resolution monitoring of different spatial chemical characteristics using common sensors (turbidity, chloride, dissolved oxygen, and oxidation/reduction sensors) that would not be feasible with traditional water sampling methods. Multi-parameter probe vent site identification is supported by elevated alkalinity and silica concentrations at these sites. The identified groundwater vent sites appear to be controlled by bedrock fractures that transport water from different sources with different contaminants of concern. Elevated contaminants, such as, arsenic and nickel and/or nutrient concentrations are evident at the vent sites, illustrating the potential of these sources to degrade water quality.

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