Water Temperature

Water Temperature affects freshwater aquatic ecosystems in numerous ways. Warming temperatures can stress aquatic animals and also allows warm-water adapted species to outcompete species adapted to cooler temperatures. As temperatures continue to rise, even warm-water adapted species can become stressed and may ultimately have to move or die. Warming water can also increase oxygen demand while simultaneously reducing oxygen levels in water, further stressing aquatic animals.

How is it scored?

We scored samples using the Part 4 water quality standards from the Michigan Department of Environment, Great Lakes, and Energy. We only included April through September temperatures in this analysis. Thresholds vary by month and were 12.2 °Celsius for April, 18.3 °Celsius for May, 20 °Celsius for June through August, and 17.2 °Celsius for September. Water temperatures below the threshold were scored a 100% and water temperatures above the threshold were scored a 0%. Stations sampled multiple times were averaged. Station scores within a watershed were averaged to score watersheds, which were area-weighted to calculate an overall region score.

Table 1. Years and water quality parameters that were used to score water indicators for each watershed. We combined up to 7 years of data due to limited data availability. TN = Total Nitrogen, NN = Nitrate + Nitrite, TSS = Total Suspended Solids, DO = Dissolved Oxygen. Cells with an N/A indicates data were not available.

Data sources: National Water Quality Monitoring Council Water Quality Portal (waterqualitydata.us) and River Raisin Watershed Council.