The following outlines the deviations in this dataset from the NHD 1:24,000 open water polygons:

1. NHD 1:24,000 data did not exist for the Canadian side of Lake Huron. For this shoreline, the summarized NHN 1:20,0000 shoreline was used from the synchronized Watershed Boundary Dataset (NHN data is available in ~50 work units for the Great Lakes and would have been time consuming to process)

2. The NHN shoreline included in the WBD did not cover the St. Mary’s River, so a shoreline layer provided by the Ontario Ministry of Natural Resources (OMNR) that was created from the Ontario Hydro Network (OHN) was used.

3. Islands for the St. Mary’s River and some larger islands in Lake Huron were added from the NHN

4. A small number of islands that were notably missing were digitized and added to the Lake Michigan layer at the 1:24,000 scale.

5. A set of EPA bays was used to add additional, prominent and bays and some river mouths to the Great Lakes shoreline basin wide.

Year data layer created: 2014

Data Download Date:

National Hydrography Dataset 1:24,000 (1/13/2013)

Watershed Boundary Dataset (acquired 1/7/13 from Kimberly Jones, USGS kjones@usgs.gov)

NHN (downloaded 1/23/2013)

OHN Shoreline (acquired 12/16/2013 from John Gaiot, OMNR john.gaiot@ontario.ca)