Our map shows four basic measurements of water conditions along the Rock River: temperature, dissolved oxygen, pH, and conductivity. We're focusing on these four both because their considered "core" water quality metrics and because real-time probes are readily available.
Note that these four measurements and our single snapshot of the river are not sufficient to make overall judgements of the water quality. A thorough analysis would require additional measurements, such as phosphorus, and measurements throughout daily and annual cycles.
Temperature, measured in Celsius, is important for determining what aquatic life will survive and thrive in our waters. Warmer water is generally less desirable for a variety of reasons: 1)the solubility of oxygen decreases and oxygen available to aquatic life is generally lower, 2)... Increased surface runoff and removal of riparian vegetation tend to increase stream temperatures. Depending on the size of the stream, temperature may vary by several degrees through the course of a single day.
Dissolved oxygen (DO), measured in milligrams per liter (mg/l), indicates the amount of oxygen available to aquatic life and is added both through aeration at the water's surface and through aquatic plant photosynthesis. Dissolved oxygen levels typically cycle throughout the day with a peak around sunset and low point at sunrise. Therefore, we'll generally expect rising DO values throughout our monitoring day. More details
pH, is a unitless measure of how acidic (values below 7.0) or basic (values above 7.0) a substance is. Natural, unpolluted rainfall is slightly acidic (between 5 and 6), but movement of water through our soils and groundwater systems tends to increase the pH. Many substances in water such as calcium can serve as "buffers" and limit changes in pH as acids or bases are added. A generally acceptable range for pH is between 6.5 and 9.0. pH values outside this range may indicate contamination from industrial or mining activity. In addition, lower pH values help mobilize heavy metals in the water column and lead to toxic conditions for aquatic life.
Conductivity, is measure of how conductive water is to electricity across a distance. Water with few dissolved substances is more resistance than water with more dissolved minerals. For example, salt water is generally much more conductive than fresh water. Conductivity is measured in microsiemens per centimeter (µS/cm). High conductivity readings or rapid changes in conductivity can indicate pollution that could impact aquatic life. In addition, conductivity can be used to approximate the total dissolved solids (TDS) in the water. More details