Wisconsin's Outstanding and Exceptional Resource Water (OERW) designations are designed to include Wisconsin's cleanest waters. The OERW dataset was first developed in the 1990s using narrative descriptions from the state’s OERW designations described in NR102 and the state’s 1:24,000 scale hydrography dataset using 7.5 minute USGS topographic quadrangle maps. The OERW spatial data quality has been reviewed by GIS specialists working with biological field staff and using more detailed landmarks and data over time. The accuracy of the delineations continue to improve with the use of improved technologies and tools. Year 2006 designations were derived by selecting and copying applicable features from the 1:24,000 scale hydrography dataset.