Watersheds for U.S Geological Survey National Stream Quality Accounting Network (NASQAN) sampling sites 1996-2000.
A digital representation of the watersheds of 43 sites on large river systems sampled by the 
National Stream Quality Accounting Network (NASQAN) of the U. S. Geological Survey 
(USGS) in 2000 was created primarily from 1:250,000 hydrologic units(HUCs) in the United 
States. Watershed information from Canada and …