A map was VERY quickly flashed on the screen on Smallville tonight (sadly, I wasn't taping it), showing the location of Metropolis. It looks to be in the place of Wichita (give or take 40 miles or so), which does have the Arkansas River (matching Metropolis having a dock district). The geography is too flat for the sorts of things we've seen on Smallville (matching northeast Kansas better), but given that they really shoot around Vancouver, some allowances have to be made.
This also leads to the possibility that Smallville takes the place of Emporia KS. Emporia State is about as big as the fictional Central Kansas A&M, and having been in Emporia over the weekend I can say that the downtown is comparable to Smallville's (if a bit bigger). There's a reservoir near enough to stand in for the early ep in which lightning transfers Clark's powers to that one kid, and for the lake sometimes used on the show (i.e. the Arthur Curry ep). Emporia is about an hour or so from Wichita, fitting the proximity of Smallville to Metropolis. It's also about an hour from Topeka, maybe a little too close for Pete Ross to be so completely written out of the show. Perhaps Smallville is on the other side of Wichita, around Platt (although that's even flatter, with no large reservoir lakes nearby).
( Small spoiler behind cut. )
This also leads to the possibility that Smallville takes the place of Emporia KS. Emporia State is about as big as the fictional Central Kansas A&M, and having been in Emporia over the weekend I can say that the downtown is comparable to Smallville's (if a bit bigger). There's a reservoir near enough to stand in for the early ep in which lightning transfers Clark's powers to that one kid, and for the lake sometimes used on the show (i.e. the Arthur Curry ep). Emporia is about an hour or so from Wichita, fitting the proximity of Smallville to Metropolis. It's also about an hour from Topeka, maybe a little too close for Pete Ross to be so completely written out of the show. Perhaps Smallville is on the other side of Wichita, around Platt (although that's even flatter, with no large reservoir lakes nearby).
( Small spoiler behind cut. )