Outstanding Iowa Waters (OIW) are those surface waters that Iowa DNR has classified as an outstanding state resource water. Where high quality waters constitute an outstanding state resource, such as waters of exceptional recreational or ecological significance, that water quality shall be maintained and protected.

More information about OIW-designated waterbodies and the protections afforded to them can be found at the following locations:

• Iowa DNR Antidegradation Procedure - Antidegradation refers to federal regulations designed to maintain and protect high quality waters and existing water quality in other waters from unnecessary pollution.
• Iowa OIW Map (PDF)
• Iowa OIW Map - Iowa GeoData (Shapefile)
• Iowa OIW Map - ADBNet live map