Inside the Gunnison Tunnel, the first major water diversion system in the U.S. — The #Colorado Sun

East Portal Gunnison Tunnel gate and equipment houses provide for the workings of the tunnel.
Lisa Lynch/NPS

From The Colorado Sun (Jason Blevins). Click through for the cool photos, here’s an excerpt:

After more than a half-hour splashing through the dank dark of one of the world’s longest irrigation tunnels, Dennis Veo grins in the sunshine showering the cliffs of the Black Canyon of the Gunnison River…

The 120-year-old, 5.8-mile tunnel was the largest irrigation tunnel in the country when it opened in 1909. It was also the first major transmountain diversion in the U.S., becoming a model for moving Western water beneath mountains, connecting wet basins with dry deserts.

Today, the Gunnison Tunnel can move more than 500,000 acre-feet of water a year, more than the entire Eastern Slope draws from the Upper Colorado River Basin.

That water, roughly 1,150 cubic-feet-per-second when filled to the ceiling of the granite-blasted tunnel, irrigates about 83,000 acres for 3,000 members of the Uncompahgre Valley Water Users Association and also delivers water to more than 50,000 people in the three-county Project 7 Water Authority. The water that pours from the Gunnison Tunnel is the lifeblood of the Uncompahgre Valley, flowing through 128 miles of major canals and 438 miles of lateral ditches in Montrose and Delta counties.

“We are the largest diverter of water in Colorado,” says Steve Anderson, the second-generation general manager of the Uncompahgre Valley Water Users Association. “We can take about the same as the entire Front Range takes from the Colorado River. And about the same as the Metropolitan Water District of Southern California takes out of the Colorado River. That is a lot of water.”

Gunnison Tunnel via the National Park Service

An engineering marvel

In the late 1800s, it became clear that the fickle flows of the Uncompahgre River alone could not irrigate enough acres in the river valley between Delta and Montrose. There were close to 100,000 acres homesteaded by farmers but only enough water to irrigate a fraction of that.

An ambitious plan to connect the Gunnison River with the Uncompahgre River valley started in the early 1900s, when a pair of intrepid engineers with the local power company and the U.S. Geological Survey descended the Black Canyon of the Gunnison River on rubber air mattresses. With cameras and rudimentary surveying equipment, they searched for a place to build a diversion dam and tunnel.

The first bore of the Gunnison Tunnel opened in 1909. It was the first major project approved by the Department of the Interior under the 1902 Reclamation Act. More than 26 men died during construction of what was then the longest irrigation tunnel ever built. Countless more workers were maimed. The manual diggers — crews of 30 men working around the clock from both ends of the tunnel — were off by only 6 inches when they met in the middle, Veo said. By 1912, water was flowing through the tunnel and irrigating crops from Delta to Montrose.

In 1973, the American Society of Civil Engineers honored the Gunnison Tunnel as a Historic Civil Engineering Landmark. A few years later it was listed on the National Register of Historic Places…

The Gunnison Tunnel is the critical link of the Wayne N. Aspinall Unit, one of the four projects that make up the 1956 Colorado River Storage Project…

The other units created under the 1956 Colorado River Storage Project Act include the Flaming Gorge Dam on the Green River in Utah, the Navajo Reservoir in New Mexico and Lake Powell in Utah. The network of reservoirs and dams are used by Upper Colorado River Basin states to store water and generate electricity as part of the Colorado River Compact that divides up the river between seven states and Mexico…

The engineering masterpiece has sustained a lush vibrancy along the Uncompahgre River. It’s pretty simple to imagine what the valley would look like without that tunnel, says John Harold, who farms corn, onion and beans in the valley.

Map of the Gunnison River drainage basin in Colorado, USA. Made using public domain USGS data. By Shannon1 – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=69257550

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