As far as I know the walleyes have spawned on most rivers open to fishing in Wisconsin. The Tomahawk area could be one exception. Another overlooked river system for spring walleyes is the Menominee Rivers several dams upstream from where it enters Michigan. There is great fishing under many of these dams, and the run is a good week to two after most other dams in Wisconsin.
Even if the fish have spawned great fishing still can be had on rivers near or downstream of dams. Fish seam to go on a short feeding spree right after the spawn and can be caught during the day on live bait or at night on cranks.
The great thing about this spring fishing is that you are out on the water, it has been a long winter and this is a good chance to make sure your equipement and skills are in good order. See you on the water.