Attributes for NHDPlus Catchments (Version 1.1)for the Conterminous United States: Contact Time, 2002
This data set represents the average contact time, in units of days, compiled for every catchment of 
NHDPlus for the conterminous United States. Contact time, as described in Wolock and others (1989), 
is the baseflow residence time in the subsurface. The source data set was the U.S. Geological Survey's 
(USGS) …