Phosphorus is an indicator of too much phosphorus in the water. Phosphorus attaches to sediment particles, so phosphorus and sediment pollution are linked. Phosphorus is an essential nutrient for all plants and animals. But too much phosphorus in the water causes algae to grow in large, dense algal blooms, which depletes oxygen for fish and other aquatic organisms.
How is it scored?
We scored samples as pass/fail using US EPA ecoregion-specific thresholds (regions 55 and 57 = 0.07625 mg/L, region 56 = 0.033 mg/L). Samples above the threshold failed (0%) while samples below thresholds passed (100%). 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.
Data sources: Total phosphorus (TP) data from the National Water Quality Monitoring Council Water Quality Portal (waterqualitydata.us), the Huron River Watershed Council, and from the River Raisin Watershed Council.