How was the health of Western Lake Erie calculated?

This report card provides a transparent, timely, and geographically detailed assessment of health in Western Lake Erie and it's watershed using data from 2018 defined as the progress of five indicators toward scientifically-derived thresholds or goals. The indicators are combined into two overall health scores, one score for the Lake, and one for the Watershed.

Each sample is compared to a threshold to calculate a score from 0 to 100. All sample scores are averaged for each sampling location to reach a station score. All stations in each region are averaged to a region score. Region scores are area-weighted to get the overall score.

Overall Health Index

The Western Lake Erie report card compares 11 lake indicators (total phosphorus, dissolved phosphorus, nitrate-nitrate, chlorophyll a, walleye, yellow perch, emerald shiner, bloom index, source water toxin, and recreational toxin) and 10 watershed indicators (total phosphorus, dissolved phosphorus, total nitrogen, nitrate-nitrite, source water toxin, total suspended solids, fish, macroinvertebrates, habitat quality, and fish consumption) to scientifically derived thresholds or goals. The lake indicators were combined into an overall lake health index, which is presented as a subregion percent score. The watershed indicators were combined into an overall watershed healh index, which is presented as a subregion percent score. Both scores were calculated as an average of the subregions weighted by geographic area.