Based off my experience fishing pool 2 I have started to think a large number of walleye spawn in the Minnesota River. Definetly still a good amount of walleye spawn by the dam and Minehaha creek and probably a couple other locations near the confluence.
Here is a study from the late 90s, worth a read if you are into this kind of stuff. They located a good amount of walleye and sauger through radio transmitters in the Minnesota river during spawning time too.
https://files.dnr.state.mn.us/publications/fisheries/investigational_reports/482.pdf
River conditions are definitely different now then during this study but I bet there are still a lot of walleye that go up the Minnesota river.
let me know your thoughts