The Gunnison River is a major tributary of the Colorado River, contributing about one-third of the Colorado’s flow at the Colorado-Utah state line. The basin drained by the Gunnison stretches from alpine meadows and forests along the Continental Divide to the arid canyon country around Grand Junction. This rural basin is home to cattle ranches, cornfields and orchards and is also a major destination for outdoor recreation. It also includes vast swaths of public lands. The Gunnison River and its major tributaries are controlled by dams and diversions.
The Gunnison River basin contains several environmentally and culturally distinct subregions. The Upper Gunnison Basin is bounded by the Continental Divide on its eastern edge. Blue Mesa Dam, which creates Colorado’s largest water body, at an elevation of 7,500 feet, marks the upper basin’s downstream extent. Cattle ranching and hay production are the primary agricultural activities due to the short growing season. Crested Butte Mountain Resort brings skiers in winter, and rafting and fishing are popular at other times of year. Gunnison is the area’s largest town, with a population of 15,725.
Below Blue Mesa Dam, the Gunnison River plunges into a narrow, steep canyon. Black Canyon of the Gunnison National Park provides a window into this dramatic landscape.
Farther west, the Uncompahgre River drains the San Juan Mountains and the Uncompahgre Plateau to form the Uncompahgre Valley, which contains the largest share of Gunnison Basin agriculture. In its middle reaches, the valley is divided from the main stem of the Gunnison River by a narrow ridge. The completion of the Gunnison Tunnel in 1909 breached that divide to bring additional water to the valley to irrigate alfalfa, corn, and other field crops. Montrose, with approximately 19,000 people, is the valley’s largest town.
The North Fork of the Gunnison River and its tributaries form the North Fork Valley, which contains such towns as Paonia and Hotchkiss and is known for orchards, vineyards, and small-scale agritourism. Cattle, sheep, and hay are also raised there.
The town of Delta, with a population of nearly 9,000, lies at the confluence of the Gunnison and Uncompahgre rivers. Downstream, the Gunnison River flows through more canyons on its way to the Colorado River at Grand Junction. This section of river provides critical habitat for four endangered fish species: the Humpback chub, Boneytail chub, Colorado pikeminnow, and Razorback sucker.
Until the late 1800s, the Gunnison Basin was inhabited by the Southern Ute people, who migrated between the mountains and valleys with the seasons. In the 1870s miners arrived in the headwaters and agricultural communities sprang up in the lower valleys after the Utes were expelled in 1881.
Because most of the basin receives fewer than fifteen inches of precipitation per year, irrigation developed along with agriculture. This began with private efforts to dig ditches and build dams, many of which still exist. In the early 1900s the federal Bureau of Reclamation got involved, dramatically increasing the scale of water development.
The oldest Bureau of Reclamation project in the Gunnison Basin is the Uncompahgre Project, which included both the Gunnison Tunnel and the later construction of the Taylor Park Dam and Reservoir far upstream. The Taylor Park Reservoir served two purposes: storing water for Uncompahgre Valley farmers to use late in the growing season and preventing water users in the Arkansas Basin, just across the Continental Divide, from appropriating Taylor River water.
The largest Bureau project in the basin is the Aspinall Unit, which includes Blue Mesa Dam and two downstream dams on the Gunnison River: Morrow Point and Crystal. Together, these reservoirs can store just over 1 million acre-feet of water. The unit, completed in 1976 as part of the Colorado River Storage Project, generates electricity and helps meet obligations to the downstream states that share rights to the Colorado River.
While the dams and reservoirs on the Gunnison River and its tributaries have served agriculture and communities well, they took a toll on the environmental health of the river. In the twenty-first century, two important documents addressing that impact became cornerstones for how water is managed: the 2008 Black Canyon Decree and the 2012 Final Environmental Impact Statement (EIS).
The Black Canyon Decree, developed after years of legal controversy and negotiation, set flow targets to restore and maintain the health of the environment in Black Canyon of the Gunnison National Park. In 2012 the Bureau of Reclamation released the EIS that guides how the Aspinall Unit reservoirs are managed to benefit endangered fish species downstream while still serving the unit’s original purposes. Both documents set targets for short-term peak flows, as well as minimum flows, and the Black Canyon Decree is incorporated into the EIS.
Water quality has also become an increasingly important factor in water management, as salt and selenium leaching from Gunnison Basin soils has caused problems for downstream farmers and native fish. As a result, many miles of canals in the Uncompahgre Valley have been lined and farmers have received assistance to transition from flood irrigation to more efficient methods. Additionally, some headwaters streams are afflicted by acidic, heavy metal–laden water draining from old mines. Cleanup efforts include a Superfund site on Elk Creek near the town of Crested Butte.
More recently, recreation has also become a factor in water management. Whitewater parks have been established near Gunnison, Montrose, and Ridgway, with structures placed in the rivers to enhance the whitewater boating experience. The Gunnison Whitewater Park has its own water right. Recreation can also influence the operation of existing facilities. For instance, releases from Taylor are timed to accommodate boaters and anglers as well as irrigators. In addition, some aging diversion structures have been reengineered to benefit fish and boaters as well as irrigators.
In 2015 roundtables of water managers and stakeholders from each major river basin in Colorado developed plans to define each basin’s water needs and set project priorities. The Gunnison Basin Roundtable defined the protection of existing uses as its primary goal, reflecting concern about growing demands from urban centers on the east side of the Continental Divide and downstream in the Colorado River Basin as well as the possibility of reduced streamflow due to climate change.
Other goals in the basin plan include discouraging conversion of productive agricultural land to other uses, reducing agricultural water shortages, and modernizing critical water infrastructure. An additional goal—to describe and encourage the beneficial relationship between agricultural, environmental, and recreational water uses—reflects efforts to bridge differences between competing water interests in order to strengthen the water-based values of the entire Gunnison Basin.