Excess nutrients promote excessive aquatic plant growth—eutrophication—which has been a serious problem in the watershed. The overgrowth of algae and aquatic plants leads to large daily swings in dissolved oxygen and pH (acidity) levels, negatively affecting fish and aquatic habitats. Eutrophication also severely impairs the enjoyment of the river’s scenery and use for recreation and leads to a sewage-like smell when it decomposes. Phosphorus is generally the controlling nutrient for freshwater systems. Both phosphorus and nitrogen concentrations are used to indicate the potential for eutrophication. Total phosphorus (TP) scores are calculated based on a comparison with background phosphorus concentrations typical for EPA Ecoregion XIV.