Hay, river, c.530 mi (850 km) long, rising in several headstreams in NE British Columbia and NW Alta., Canada, and flowing generally NE through NW Alta., over Alexander Falls, and into Great Slave Lake. Its valley, a principal north-south route, is followed by a highway and a railroad.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.