Low-resolution vectors representing major rivers of the world, stored as
lines in shapefile format with coordinates in latitude (Y) and longitude
(X) in degrees.  A 'Name' attribute provides names for most rivers.  The
coordinate sampling is equivalent to a scale of 1:30,000,000.  This data
set is suitable for global displays.

Source
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The raw coordinate data were derived from the Digital Chart of the World
(DCW) browser layer ('Streams, rivers, channelized rivers'), published by
U.S. National Geospatial-Intelligence Agency (NGA), formerly National
Imagery and Mapping Agency (NIMA).