Drainage in the Colorado River Basin

The Green, San Juan, and Gila River Drainage Basins are the major contributors to the Colorado River Basin drainage.  The maps above are out of propotrion with each other, particularly the San Juan, but give a general indication of their drainage areas when compared to the map of the entire basin on the right.  These maps show that the Grand River (present-day Colorado above its confluence with the Little Colorado) has a very small drainage basin compared with the other basin tributaries (the Green alone is 70% greater).  However, it should also be noted that spring snow-melt in the Rockies is a major contributor to basin drainage.  Lesser tributaries, including the Virgin, Gunnison, and Little Colorado during White Mountains snow-melt, also make a major contribution to the basin.

Grand River?  Much confusion surrounds the naming of Green, Grand, and Colorado Rivers, and borders Grand, Glen, and Marble Canyons.  See Satire on menu selection Navajo Bridge - History  if you are interested in that story of intrigue.