Water across the Divide

How the failure of an aged ditch got in the way of Wilderness

  • The intact Grand Ditch, circa 1983, winds through the western edge of Rocky Mountain National Park.

    Courtesy NPS, Rocky Mountain National Park
  • granditchbreach.jpg

    The ditch breached in 2003, releasing a flood that carved a massive gulley, killed thousands of trees, and covered nearby wetlands in sediment.

    Library of Congress, Prints & Photographs Division, HABS, HAER COLO,25-GRLK.V,2-3

Name The Grand Ditch

Age 119 years

High maintenance In the ditch's early days, farmers sent laborers to Poudre Pass each spring to shovel snow from the channel so its water could flow.

Getting there From the Upper Colorado River Trailhead on Trail Ridge Road (U.S. 34), hike 3.5 miles to Lulu City. The scar from the breach slices straight down the forested mountainside below the shelf created by the Grand Ditch.


Before dawn on May 30, 2003, something breached the Grand Ditch, which slices across steep mountainsides in the backcountry on the western edge of Rocky Mountain National Park. An avalanche, perhaps, or a slope failure, abruptly sent the ditch's flow pouring downhill at some 70 cubic feet per second -- enough to fill one Olympic-sized swimming pool every 21 minutes. It quickly picked up soil, gravel and boulders, and uprooted entire trees.

By the time ditch riders for the Fort Collins-based Water Supply and Storage Company, the ditch's owners, could choke off the flood, it had carved a white scar in the mountainside 167 feet wide and several stories deep, clearly visible on Google Earth. It had poured into Lulu Creek far below, gouging a gully up to six feet deep, buried the boggy meadows of the Lulu City wetlands in one to two feet of sand and uprooted or smothered some 20,000 trees. Carried by the Colorado River, it formed a visible delta in Shadow Mountain Reservoir, 28 miles downstream.

The Grand Ditch is the second oldest of more than two dozen Colorado trans-basin diversions, ditches or tunnels that siphon water from one river basin into another. A group of investors who coveted West Slope water dug the first segment of the ditch in 1890, 25 years before Rocky Mountain National Park was established. It began as a relatively modest mile-long, hand-dug channel that sent water from the headwaters of the Colorado across the Continental Divide at 10,175-foot-high Poudre Pass and into the Cache la Poudre River to nourish farms 100 miles away on the plains. (Even then, the bulk of Colorado's population as well as its agriculture was located on the state's semi-arid eastern plains, while most of the state's water, then and now, comes from snowfall on the less-populated Western Slope.)

Water Supply and Storage Company took over the ditch in 1891, and over the next 40 years, workers used picks, shovels, and dynamite and eventually steam shovels to gradually extend the ditch's 20-foot-wide shelf across 14.3 twisting miles of steep mountainsides. Ultimately, the Grand Ditch intercepted up to 40 percent of the runoff of the Upper Colorado River. Today, although farms still lease the water, the fast-growing Front Range cities of Thornton, Greeley and Fort Collins own the majority of the ditch company's shares.

After the ditch breached in 2003, the Park Service began the long process of assessing damage to the Upper Colorado River Valley's forests, streams, wetlands, and backcountry trails, bridges and campsites. Three years later, after much foot-dragging by the Bush administration, the U.S. Department of Justice sued the ditch company for $12 million in damages. Then-Colorado Rep. Marilyn Musgrave, R, originally tried to block legislation designating the park's backcountry as wilderness in order to protect the ditch company from liability. But in 2008, the company agreed to a $9 million settlement, the largest ever under the Park System Resources Protection Act. The following year, Congress passed a bill co-sponsored by Musgrave designating most of Rocky Mountain National Park -- except existing development like the Grand Ditch -- as wilderness.

The white scar gouged by the Grand Ditch breach is still clearly visible, along with the dead trees. The Lulu City wetlands are green again, but the formerly diverse patchwork of marsh is now dominated by a single species of sedge, according to Paul McLaughlin, the national park's Grand Ditch breach restoration coordinator. He and his colleagues are evaluating data to help determine how to repair the ecological damage left by the flood.

The sediment-choked channel of the Upper Colorado River is in critical need of restoration, says McLaughlin. Any increase in river flow -- whether from the higher peak spring flows predicted by climate change models, or from possible abandonment of the expensive-to-maintain Grand Ditch -- would flood the current constricted channel and destroy riverside habitat. But McLaughlin believes the river can be restored. He points to old photos of Lulu City, a mining camp that sat on the banks of the Upper Colorado in the 1870s, and asks us to imagine all that water once again flowing freely down a sinuously curving channel lined by tall willows. 

Susan J. Tweit is a naturalist, and the author of several books in Salida, Colorado.

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