Actually it's kind of a 'both.' You have BPA as part of the larger Columbia Basin Power grid. Here's a map (expandable) that shows all the dam locations (save for those in Canada).
There's a another thread going where in I posted a link to an 'interactive map.' Looks similar to the above, but if you 'click' on the dam it will give you a short over view of the facility (and if it provides fish passage).