Complex sentence: The Colorado is joined by over 25 significant tributaries, of which the Green River is the largest by both length and discharge, taking drainage from the Wind River Range of west-central Wyoming, Utah's Uinta Mountains and the Rockies of northwestern Colorado.
Split into simpler sentences: The Colorado is joined by over 25 significant tributaries, of which the Green River is the largest by both length and discharge. The Green takes drainage from the Wind River Range of west-central Wyoming, from Utah's Uinta Mountains and from the Rockies of northwestern Colorado.