We know from studies of relatively undisturbed Ontario lakes that Lake Simcoe has been impacted by human activities. In recent years, the most obvious of these impacts have been nuisance aquatic plant growth and declining coldwater fisheries, which themselves are symptoms of more complex problems. Although many chemical parameters and plant and animal species are affected by human activities, phosphorus concentrations, oxygen content, and the state of the fish community provide an excellent indication of the overall state of the watershed. They provide useful, measurable benchmarks for ecosystem health and can be used to set targets for watershed management.

The first comprehensive studies of Lake Simcoe water quality were conducted between 1971 and 1974 by the Ontario Ministry of the Environment (formerly the Ontario Water Resources Commission), although many more have been undertaken since. Water quality of the lake and the rivers feeding it has been and continues to be monitored through the joint efforts of the Ministry of the Environment, the Ministry of Natural Resources and the Lake Simcoe Region Conservation Authority. Many of the monitoring programs that are currently occurring in the watershed were initiated decades ago. Such long-term studies are extremely valuable for identifying and investigating long-term trends in the watershed that would otherwise remain inexplicable.

Water Quality Issues