The Continental Divide: Where Colorado Water Decides Its Ocean

At Milner Pass on Trail Ridge Road, at an elevation of ten thousand seven hundred fifty-nine feet, a small sign marks the Continental Divide. A raindrop falling on the west side of that sign will eventually reach the Pacific Ocean, via the Colorado River. A raindrop falling on the east side will eventually reach the Gulf of Mexico, via the South Platte and the Missouri and the Mississippi. The two drops land less than a foot apart and never see each other again.

The Continental Divide runs the length of the Rocky Mountains through Colorado, an irregular ridgeline that serves as the hydrological backbone of North America. It does not follow state borders or county lines or anything human beings drew on a map. It follows the high ground.

The problem Colorado has always had with its Divide is that geography and population ended up on opposite sides. Approximately eighty percent of Colorado's precipitation falls on the western slope. Approximately eighty percent of Colorado's population lives on the eastern slope, in the cities along the Front Range. Denver, Colorado Springs, Pueblo, Fort Collins: all east of the Divide, all needing water from the wrong side of the mountain.

The solution has been tunnels. The Moffat Tunnel, completed in nineteen twenty-eight, punches just over six miles through the Continental Divide beneath James Peak, primarily carrying trains, with a smaller parallel bore later enlarged to move water east. The Roberts Tunnel under the Divide feeds the Denver metro area. The Adams Tunnel, which runs under Rocky Mountain National Park for about thirteen miles and carries water from Grand Lake on the west slope to the Estes Park valley on the east, is one of the longest water tunnels in the United States.

The divide is a geographical fact. The infrastructure built to defeat it is a human obsession that has been running for over a century and is not finished.