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Outstanding and Exceptional Resource Waters
Protecting Wisconsin’s Best

O/ERW Designations

Wisconsin has designated many of the state’s highest quality waters as Outstanding Resource Waters (ORWs) or Exceptional Resource Waters (ERWs). Waters designated as ORW or ERW are surface waters which provide outstanding recreational opportunities, support valuable fisheries and wildlife habitat, have good water quality, and are not significantly impacted by human activities. ORW and ERW status identifies waters that the State of Wisconsin has determined warrant additional protection from the effects of pollution. These designations are intended to meet federal Clean Water Act obligations requiring Wisconsin to adopt an “antidegradation” policy that is designed to prevent any lowering of water quality – especially in those waters having significant ecological or cultural value. Download a spreadsheet of the ORW/ERWs in Wisconsin.

What is the difference between ORWs and ERWs?

ORWs receive the state’s highest protection standards, with ERWs a close second. ORWs and ERWs share many of the same environmental and ecological characteristics. They differ in the types of discharges each receives, and the level of protection established for the waterway after it is designated.

  • ORWs: ORWs typically do not have any point sources discharging pollutants directly to the water (for instance, no industrial sources or municipal sewage treatment plants), though they may receive runoff from nonpoint sources. New discharges may be permitted only if their effluent quality is equal to or better than the background water quality of that waterway at all times—no increases of pollutant levels are allowed.

Number of ORW/ERW Waterbodies

  • ERWs: If a waterbody has existing point sources at the time of designation, it is more likely to be designated as an ERW. Like ORWs, dischargers to ERW waters are required to maintain background water quality levels; however, exceptions can be made for certain situations when an increase of pollutant loading to an ERW is warranted because human health would otherwise be compromised.

How many waters in Wisconsin are ORW/ERW?

Of Wisconsin’s 15,000 lakes and impoundments, 103 are designated as ORW—fewer 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.

Find O/ERW Waters

Find O/ERW Waters

To look up specific waterbodies, you can use several sources:

Wisconsin Administrative Code NR 102
Waters currently designated as ORWs and ERWs are listed in Wisconsin’s Administrative Code in chapters NR 102.10 (ORWs) and NR 102.11 (ERWs). The code is the legally authoritative source, though it can be complex to interpret. If you would like assistance in determining whether a specific water you are interested in is an ORW/ERW, contact the ORW/ERW Coordinator, Kristi Minahan, at 608-266-7055 or

Maps of ORW/ERW

Lists of ORW/ERW
NOTE: In using the documents below, be sure to use both those from before 2006 and those from the 2006 addition, in conjunction with one another.

Last revised: Monday January 13 2020