Hydrography Polygons Representing DuPage County, Illinois hydrography: lakes, ponds, wetlands, rivers, streams, creeks, and ditch polygons. The DuPage County surface hydrography coverage reflect extensions to the original surface hydrography ARC/INFO coverage that was built from 1:2400 scale aerial photography and planimetric mapping. The original 1991-92 coverage embraced a simple line-based structure with no polygon definitions. Extensions to the original coverage structure are meant to accommodate more sophisticated Department GIS application needs such as area-based (polygon) measurements, attribute driven thematic displays, network modeling to support hydrologic/hydraulic flow routing, and stream corridor management. An extensive quality control effort was completed in 1996. Updated Spring\Fall 2006 using most current orthophotography. Additional updates have been made to this dataset, and have been completed using the Spring 2009 orthophotography. Updates will be made as needed.