What river or rivers were in this movie?

It is the Blackfoot River in Montana and yes, it is very polluted as a result of mining companies not adequately cleaning up after themselves and hazardous materials leaking into the Blackfoot and many other rivers. The book Collapse, by Jared Diamond goes into more detail about it if you are interested.

The river this takes place on and the river this was filmed on are two totally different rivers.

From everything I can gather on the internet, the river scenes were shot on the Madison, Gallatin and Yellowstone rivers - all which are within one hour or less of Bozeman. I actually live about an hour from Bozeman and have rafted and fly fished on the Yellowstone and Madison rivers. However, I have not been able to pinpoint the exact spots for the shots, although the rivers do and can change over time. In fact, I rafted both these rivers within the last week, and am taking my parents on a Yellowstone river raft trip this weekend. Next summer I plan on rafting the Blackfoot and Clark fork also, when the flows are higher.

I was in Livingston in June and was told that much of the film was made there. I assume that the Yellowstone River was the setting for some of the scenes.

OK... So the movie (and book) mostly take place in Missoula, and the surrounding areas. (blackfoot and clark fork rivers) (though, anyone who actually fly fishes missoula, knows it would probably be the blackfoot, as the clark fork is too deep, and rapid to do much good fly fishing... especially south of the milltown dam (which was just removed a few months ago).

The filming of the movie, however was done around Bozeman. Mostly on the Madison river, though my angler friends say it also partly filmed on the Gallatin River.

Both are beautiful places to go. I live south of missoula, but Bozeman is a nice town too.

"In the novel, Maclean casts flies and reels in trout on the Blackfoot River near Missoula, but the film was shot mostly on the Gallatin River and in Southwest Montana. That was partly because the Blackfoot was not as pristine as it once was." - Bozeman Daily Chronicle, Sunday, February 26, 2012.