Restoring our Water Heritage: A Watershed Plan for the Lower Fox River Basin
Waterbodies can handle a certain amount of any substance like phosphorus (a component of fertilizer). However, above certain thresholds, these substances damage a waterbody to the point that people can no longer use it in the ways that they would like to – for recreation (swimming/boating), for drinking water, for fishing, and so on. When this happens, the waterbody is designated as “impaired” by the WDNR. The threshold level of the substance is called a “Total Maximum Daily Load,” or TMDL. Different waterbodies can handle different levels of impairing substances, and so there is no one standard that can be applied across the state. Individual standards must be developed for individual waterbodies. In fact, the state is mandated by the federal government through the United States Environmental Protection Agency (USEPA) to develop such standards.
Once the level of a substance that a waterbody can handle without becoming impaired is established, the next question is how to reduce those substances within that waterbody.
In the Lower Fox basin, the impairing substances are usually phosphorus and sediments. So how do we keep phosphorus and sediments from reaching streams and rivers? First, we need to know where those pollutants are coming from. By collecting water samples at various places in the watershed with different land covers, we can estimate the loading from different land uses such as agricultural, residential, and wooded areas. Some amount of phosphorus and sediments entered the waterbodies even before human development occurred, so there are “background levels.” These data are then entered into a computer model that estimates what and how much is entering the waters within the basin. Such modeling has been done for the Lower Fox Basin. Once the movement of pollutants within the basin is better understood, then strategies can be developed to reduce the amount of pollutants entering waterbodies from the different source areas. Partners in the Lower Fox Basin are currently developing such strategies for sediments and phosphorus.
Read the Lower Green Bay and Lower Fox Tributary Modeling Report, January 2005, by Paul Baumgart (Note that this is a 4 MB pdf file).
Read more about the Lower Fox River Total Maximum Daily Load (TMDL) at the WDNR web page: http://dnr.wi.gov/org/water/wm/wqs/303d/FoxRiverTMDL/
Read about TMDLs at the USEPA web site: http://www.epa.gov/owow/tmdl/intro.html
