ORW/ERW Listing Process & History

How is a decision made to designate waters as ORW or ERW?

Streams that are designated as ORWs or ERWs are typically identified by water quality biologists as having one or more of the characteristics named in Wisconsin Administrative Code NR 102. By assessing the qualities of the stream, or by evaluating existing data, biologists recommended specific waters for ORW/ERW designation. These recommendations are eventually brought before the Natural Resources Board and the Wisconsin Legislature for approval. To be formally recognized as an ORW/ERW, waters must be added to the ORW/ERW lists found in NR 102.10 and NR 102.11.

History of Wisconsin’s ORW/ERW

Of Wisconsin’s 15,000 lakes and impoundments, 103 are designated as ORW—less than 1%. Of Wisconsin’s 53,413 streams and rivers, 254 are designated as ORW, and 1,544 are designated as ERW. However, it can be more useful to consider stream statistics in terms of the number of stream miles rather than number of streams, since streams can be of widely varying lengths. Wisconsin has a total of ~42,000 stream/river miles in the state. Based on the current ORW/ERW list, a total of 3,179 stream miles (7.6%) have been designated as ORW, and 4,668 stream miles (11%) have been designated as ERW. It can also be helpful to consider these statistics in terms of the number of stream miles rather than number of stream segments, since segments can be of widely varying lengths. Based on the current list, a total of 3,179 stream miles have been designated as ORW, or 7.6% of the ~42,000 perennial stream/river miles in the state. A total of 4,668 stream miles have been designated as ERW, or 11% of the perennial stream/river miles in the state.