OK... there's actually a songbook for the whole Columbia River Collection. I just bought it online. I'll post lyrics later.
The book is "Roll On Columbia: The Columbia River Collection"

One source is the Woody Guthrie Foundation and Archives store:
Woody Guthrie Store

The other source is SingOut! It has the songbook and the CD for $23, or you can buy them separately:
SingOut Legacy Books
Search for "Roll On Columbia."

Parsa