At the top of the pass a series of small springs in the mountainside form a series of beaver dams.
At this point the road above and these ponds is pointed north and south. At both ends of the series of beaver dams the ponds drain, forming small creeks. The one that flows north goes perhaps 15 miles becoming Warm Springs creek along the way.
It empties into the Clark Fork of the Columbia, then flows west and north.
Perhaps 300 miles later it joins the main stem of the Columbia.
Along the way it goes through a series of dams, mostly hydro-electric. The dams are the source of most electricity in this part of the country. If I were more poetic I'd say the water from those beaver dams are powering my laptop. Eventually the Columbia joins the Pacific at Astoria
Back to the beaver dams.....the water flowing south goes through a lovely valley, becoming larger along the way thanks to other springs and small creeks.
It joins the Big Hole river and flows generally east and south.
The Big Hole is joined by other rivers and creeks, the Beaverhead and others. These flow into the Jefferson, continuing it's journey east.
The Jefferson after many miles eventually joins the Missouri.
The Missouri at this point is crystal-clear most of the time, with some very large trout. The river wends it's way across the nation, going east and south. Along it's hundreds and hundreds of miles water is taken out for agri-business large farms, and receives water from many other rivers. Eventually it reaches St. Louis.
As you know the Missouri joins the Mississippi, and eventually the water, or at least a few drops of it, hears the music of New Orleans before it goes out into the Gulf, past the oil rigs.
All from here, east and west: