The Lower DuPage River Watershed Coalition will launch a continuous dissolved oxygen (DO) monitoring network in 2014. The program is modeled after the continuous DO program developed by the DuPage River Salt Creek Workgroup and wil include a minimum of 8 stations along the mainstem of the DuPage River.
The sites will be maintained municipal members of the Coalition and are equipped with a HydroLab DS 5X equipped to collect data on DO, pH, conductivity and water temperature. Stations have a sample interval of one hour and run from April through to October (the seasonal period recognized as containing the lowest annual levels of stream DO). The project functions under a quality assurance plan agreed on with the Illinois Environmental Protection Agency.
Why continuous monitoring? DO is a water quality indicator that oscillates throughout the day as alga and other aquatic vegetation add or remove oxygen from the water column, a phenomena called diurnal variation. Variation during 24 hours can be very large, particularly at sites impounded by a dam. Such conditions are conducive to algae growth and typically experience low DO values in the mornings. Not only is low DO harmful for aquatic life, but the wide swings from low DO to high or super saturated DO levels stress aquatic life.