Hyd250 was created from the 1:100,000 scale hydrography. Certain outdated attributes in the coverage aat were removed. This generalize coverage came from the attribute seg. Arcs with seg numbers less than 500 were legacy arcs from the 1:250,000 scale hydrography. Hyd250 was created from the 1:100,000 scale hydrography. Certain outdated attributes in the coverage aat were removed. This generalize coverage came from the attribute seg. Arcs with seg numbers less than 500 were legacy arcs from the 1:250,000 scale hydrography. (description): The U.S. Geological Survey (USGS) in cooperation with Federal and state agencies, and NW Indian Tribes has produced a 1:100,000-scale River Reach data layer for the Pacific Northwest that will serve water-resource management applications for the next decade or more. The Pacific Northwest (PNW) River Reach Files are a geo-referenced river reach data layer encompasses the Columbia River Basin within the conterminous United States U.S. Environmental Protection Agency's (USEPA) reach codes. This encoding process was a primary task of the PNW River Reach Project. USEPA's reach identifiers are an integral hydrologic component in regional Rivers Study known as the Northwest Environmental Data Base(NED). NED is an ongoing effort by Federal and state agencies within the region to compile reach-specific infor