Just a heads up for Commonwealth and Bethany - Tualatin Hills does not allow floating craft on their ponds. Seems kind of funny, since Bethany butts up to private property and said private property owners all obviously have canoes / paddle boats they use, BUT - I've been told by THPRD officials that you are not allowed to launch a canoe or kayak on the lakes, and wading and swimming is likewise prohibited. Sucks, because kayak or tube fishing would be way more productive.
Every few years they actually bring a dredger barge in and dredge Bethany out and try to remove some of the weeds. Commonwealth is supposedly a lot more man made - to the point where there is a big strip of concrete at the bottom, and all that round rock you see goes all the way around the lake and all the way out to the middle. Commonwealth used to have huge carp, it does/did hold both small and largemouth bass but not in great numbers or size. Same with panfish. I used to fish it a lot more often, and it was primarily carp & trout with other species being odd-fish-out. Oregon Bass & Panfish club used to work with THPRD to stock both lakes. Not sure if they still do.