Baseline Water Quality

Dissolved oxygen is a measure of the amount of oxygen dissolved in a volume of water. The amount of oxygen found in our rivers depends on the atmospheric exchange (generally influenced by a stream’s velocity and substrate), and on water temperature. Oxygen is essential for every organism’s survival in some concentration. Therefore, not only is dissolved oxygen an important water chemistry parameter, it also limits habitat.

Dissolved oxygen measurements are taken using a dissolved oxygen Hach test kit, a YSI 550 dissolved oxygen probe, or other WDNR approved meters calibrated before entering the field.

Warm Water Fisheries: 5 mg/L
Cold Water Fisheries: 6 mg/L

pH measures acidity, or the number of hydrogen ions (H+) present in the water. Measurements range from 0 (most acidic) to 14 (most basic). Sudden changes in the pH of a waterbody can have drastic impacts on the survival of organisms that live there. Extended changes to pH can impact the function of that system.

pH measurements are taken monthly at each site using either an Oakton Acorn 5 or 5+ pH sensor.

pH must be between 6.0 – 9.0

Water clarity or turbidity is an important ecological parameter, an indicator of many water quality issues, and a defining characteristic of stream habitat for many aquatic organisms. Turbidity measurements quantify the degree that light is scattered by particles suspended in water, therefore measurements of turbidity will use different units depending on the methods and equipment being used.

Milwaukee Riverkeeper volunteers take monthly measurements of water clarity or transparency using a 120 cm transparency tube, those measurements are converted into NTU. MMSD procedures utilize electronic meters at each site that measure turbidity in FNU because of their specific light source.

≥ 54.7 cm in a 120 cm transparency tube (<10 NTU) is ideal for aquatic life. MMSD uses sensors to test turbidity, so a target of <10 FNU was used for their data.

Phosphorus (measured as Total Phosphorus) is recognized as a limiting nutrient for plant and algae growth in freshwater systems. It is generally low to absent in natural systems. Phosphorus can enter our waterways naturally from leaf litter and sediment, but when found in high levels, it is more commonly associated with anthropogenic sources like fertilizers, soaps, anti-corrosion inhibitors, and industrial discharge.

A subset of Milwaukee Riverkeeper volunteers collects samples monthly that are sent to the Wisconsin State Lab of Hygiene for analysis. Phosphorus measurements from the WDNR SWIMS database and MMSD’s routine surface water monitoring are collated and analyzed.

The Wisconsin State Standard for phosphorus is 0.075 mg/L in streams, and 0.1 mg/L in larger rivers specifically designated in state rule NR 125.

Measurements of the health of macroinvertebrate communities can be an outstanding way to reveal the long-term health of aquatic ecosystems. Although a stream’s aquatic community may not be able to define exact environmental problems, it does give us a sense of when a stream ecosystem is healthy or undergoing changes or stress. Milwaukee Riverkeeper volunteers monitor macroinvertebrate communities using a biotic index method recommended by the WDNR’s Water Action Volunteers Program. This index assesses the health of streams by monitoring the presence/absence of specific organisms with known tolerance to pollutants and dissolved oxygen levels. Based on the type of organisms that are found (tolerant, semi-tolerant, semi-sensitive, and sensitive to pollution), sites are assigned a grade ranging from 0-4. Using this scale, a grade below 1 means that no organisms were present, 1-2 represents a stream with poor community health, 2.1-2.5 indicates a stream with fair community health, 2.6-3.5 means a stream has good community health, and any values 3.6 and above are representative of excellent community health.