Imagine the maximum discharge of the Mississippi (~20,000 m^3/s) being issued in Green River, Wyoming.
What would be the environmental impact?
I’m thinking it would green up the west pretty nicely.
[Saturday update]
I put this in comments, but decided to update the post:
Someone can check my math, but ignoring wall friction in the pipeline, raising a gallon of water 6000 feet takes a head of about 0.02 kW-hrs (a little over 7 kJ). So a tiny fraction of a penny. At a speed of half a meter, for 2000 km, I get about 0.02 watts to move it up the hill (again, ignoring wall friction), over a period of six weeks or so. Seems affordable to me from an energy standpoint. Rather than pipelines, actually, it would make more sense to have a series of aquaducts with pumping stations, for less friction, and probably lower construction cost. At that velocity, 200 meters deep and 200 meters wide would do the job. I’m sure it could be optimized for speed and dimensions.
Of course, max outflow of the Mississippi might be overkill, so a useful system might be quite a bit smaller.