Grand Ditch at La Poudre Pass, Colorado

La Poudre Pass is a remote area at the northwest corner of Rocky Mountain National Park, at the headwaters of the Colorado River. There is a small pond there that could be considered the ultimate source of the great river, that drains much of the west slope of the Rockies, and the southwestern USA. Above it is a canal known as the Grand Ditch, a 14-mile long conduit that collects water from the western slope, that would otherwise flow into the Colorado River, and moves it to the eastern slope, through the ditch. The diverted water crosses the Divide at La Poudre Pass, then flows into the Long Draw Reservoir. From there it is meted out in a measured fashion, under the dam, into Cache La Poudre Creek, for use on the plains of the eastern slope, around Fort Collins, Thornton, and Greeley. The Grand Ditch has existed in some form since 1890, but didn’t reach its full length until the 1930s, when the Long Draw Reservoir was constructed. It is owned by the Water Supply and Storage Company of Fort Collins (which had to pay the Park Service $9 million for damages to the environment when the channel collapsed in 2003). Around 20,000 acre-feet of water flows through the ditch annually, an amount estimated as 20-40% of the runoff from its source, the Never Summer Mountains, which the ditch partially wraps around. The flow is measured at a gauging station, equipped with telemetry. According to the USGS, the official federal mapping agency, the Continental Divide crosses the channel just a few feet upstream from the gauging station. But given the engineering of the hydrologic divide here, their maps may need to be adjusted.