Sushi,
Follow the link below.....it shows all the dams on the Columbia and Snake Rivers. As Easy Limits noted F&H News often has info on Walleye fishing on the Columbia. Finally, if you head to the Columbia in Eastern part of the state, Potholes is not much farther and has excellent walleye fishing (see WashingtonLakes website).

http://www.nwd.usace.army.mil/ps/colrvbsn.htm