The Gunnison River Basin
The Gunnison River is formed by the confluence of the East and Taylor Rivers at Almont and flows west to Grand Junction, where it discharges into the Colorado River and contributes some 40 percent of the flow in the Colorado at the state line. Significant tributaries to the Gunnison include the North Fork of the Gunnison River and the Uncompahgre River.
The Gunnison Basin is home to the largest body of water entirely within the state of Colorado, Blue Mesa Reservoir, which has a capacity of 940,000 acre-feet (830,000 acre-feet active capacity). It is the primary storage component of the three reservoirs comprising the Aspinall Unit. Morrow Point Dam is the middle structure and its primary purpose is production of hydropower. Crystal Dam creates a stabilizing reservoir for the variable flows produced by Morrow Point Dam releases. Below Crystal lies the Black Canyon of the Gunnison River National Park.
The Black Canyon of the Gunnison was designated a national monument in 1933 and became a national park in 1999. A federal reserved water right was issued for the canyon in 1933, but efforts to quantify that right did not commence until the National Park Service filed an application with Division 4 water court in 2001. A decree was issued after nearly eight years of negotiations, with the intent of mimicking the natural hydrograph and providing peak flushing flows through the canyon. The annual peak flow is determined through a series of complex formulas using the May 1 inflow forecast to Blue Mesa Reservoir.
Another factor affecting Gunnison River flows through the canyon is the Aspinall EIS, which was adopted in January, 2012. The objective of this EIS is to provide sufficient releases of water at times, quantities, and duration necessary to avoid jeopardy to endangered fish species and adverse modification of their designated critical habitat while maintaining and continuing to meet authorized purposes of the Aspinall Unit.
The Bureau of Reclamation has a number of other storage projects in the basin, in addition to the Aspinall Unit reservoirs, including Taylor Park on the Taylor River, Ridgway on the Uncompahgre River, Silver Jack on the Cimarron River, Crawford on the Smith Fork of the Gunnison, fruit growers on Current Creek and Paonia on Muddy Creek, tributary to the North Fork of the Gunnison River.
One of the first projects developed by the Bureau of Reclamation was the Uncompahgre Project, which provides irrigation water for a variety of crops in the Uncompahgre Valley between Colona and Delta. A key component of the project is the Gunnison Tunnel, a 5.7 mile long tunnel that diverts water from the Black Canyon of the Gunnison and discharges it into a series of canals in the Uncompahgre Valley. The tunnel has a 1913 water right for 1300 cfs and supplies some 60% of the irrigation water for the 76,000 acres under the project.
Taylor Park Dam was constructed in 1937 to provide supplemental irrigation for the Uncompahgre Valley. Taylor Park Reservoir has a capacity of 106,230 acre feet. The 1975 Taylor Park Exchange Agreement allows for transfer of storage downstream to Blue Mesa Reservoir to provide the Gunnison Tunnel with a more readily available source of irrigation water. An additional benefit of this exchange was the flexibility to make releases in time and amount that would benefit recreational and agricultural users in the Upper Gunnison basin.
The Gunnison Whitewater Park is a recreational in-channel diversion water right owned by the Upper Gunnison River Water Conservancy District. The key event at the Whitewater Park is the Gunnison River Festival, which on June 23, 2012 celebrates its 10th anniversary. Events at the festival include a community raft race, raft rodeo and professional kayaking.
Agriculture is the largest user of water in the Gunnison Basin. High elevation grass pasture is the predominant crop in the Upper Gunnison basin. The North Fork Valley of the Gunnison River is renowned for their fruit orchards, featuring apples, pears and peaches. Small grains and alfalfa are the prominent crops in the Uncompahgre Valley. The cattle industry has maintained a strong economic presence in the Gunnison Basin since the 1870’s.
The Redlands Power Canal is a key diversion structure in the Gunnison Basin. It is located two miles upstream of the confluence of the Gunnison and Colorado Rivers near Grand Junction. Redlands Power Canal has a 1912 water right for 670 cfs for irrigation and hydropower. The State Engineer declared virtually the entire Gunnison Basin to be over-appropriated as a result of a 2003 Redlands call.
The City of Grand Junction is the largest municipal water supplier in the Gunnison Basin and obtains its raw water supplies from the west side of the Grand Mesa. Project 7 Water Authority is the next largest municipal provider, serving the cities of Montrose and Delta as well as other domestic users in the Uncompahgre valley.
Hydropower is a significant water use of Gunnison River water, as evidenced in the aforementioned Aspinall and Redlands projects. New hydropower projects are currently under construction at Ridgway Dam and on the South Canal. Studies are underway to evaluate the feasibility of a hydropower installation at Taylor Park Dam.
For more information on the Gunnison River, please visit http://ugrwcd.org/. For more information on Water 2012 in the Rio Grande Basin, please visit www.rgwcei.org or www.water2012.org.
The Rio Grande Interbasin Round Table will be meeting on Tuesday, July 10th from 2-5 p.m. at the Ramada Inn, former Inn of the Rio Grande. Water 2012 in the Rio Grande Basin, in partnership with the Colorado Field Institute, will be hosting a summer tour of the Rio Grande Reservoir on Saturday, July 14th. All participants must register through the website.