Irrigating Wyoming – It’s Complicated, Involves Lots of Dams And Careful Monitoring

In central and southern Wyoming, a system of dams, canals and irrigation that allows agriculture to thrive today goes back to the vision of the first U.S. president to ever live west of the Mississippi River -- Teddy Roosevelt.

DK
Dale Killingbeck

May 05, 20247 min read

An overview of the Guernsey Dam, which feeds agriculture and ranching operations downriver.
An overview of the Guernsey Dam, which feeds agriculture and ranching operations downriver. (Bureau of Reclamation)

Quenching the thirst of western Nebraska sugar beets and dry beans or moistening the roots of Wyoming hay and wheat required a near-miraculous effort at the time to transform arid high desert ground.

In central and southern Wyoming, a system of dams, canals and irrigation that allows agriculture to thrive today — and recreation — goes back in part to the vision of the first U.S. president to ever live west of the Mississippi River.

When Theodore “Teddy” Roosevelt found himself president of the United States in 1901 after the assassination of William McKinley, he pushed for the Reclamation Act of 1902 that would set in motion a flood of dam-building to allow for the homesteading of lands in the water-parched central United States, which includes parts of Wyoming and western Nebraska.

A headline in the Evanston Wyoming Press on Sept. 10, 1904, praised Roosevelt as “irrigation’s most staunch friend and thereby a benefactor to millions yet unborn. He has lived in the arid regions and fully realizes their needs.”

Now 120 years later, Mahonri Williams, chief of the Resources Management Division at the Wyoming area office of the Bureau of Reclamation, manages Wyoming’s legacy of Roosevelt’s vision.

Williams’ office controls a series of dams and reservoirs east of the Continental Divide that include the North Platte and Kendrick projects that provide irrigation water to hundreds of thousands of acres in central and southern Wyoming, as well as western Nebraska.

As Williams looks to the irrigation season this year, he said projections for water look good. His agency monitors snowpack conditions and rainfall, and plugs it all into computer models that estimate the amount of runoff and when it will arrive.

“Based on that, we have reservoir operation computer models that we use to simulate the operation of the reservoirs and make decisions as to how much flow we want to have in the river at certain times of year,” he said. “Our objectives are that we want (to meet) our requirements for irrigation demands and we want to avoid flooding situations.”

Williams said the mission is to store runoff, make irrigation deliveries, generate power when possible and “not have flows too high or too low throughout the system.”

“We’ve seen a lot of different things that nature has provided, but each year is a new year, so we adjust our operations based on conditions that we see,” he said. “We are looking at forecasts a little above average in our April forecasts and we will be updating our forecasts for (this) month.”

  • The Pathfinder Dam was the lynchpin of bringing water to arid centeral and easter Wyoming.
    The Pathfinder Dam was the lynchpin of bringing water to arid centeral and easter Wyoming. (Carol M. Highsmith Archive)
  • Workers at the Pathfinder Dam lay the first stone in 1906.
    Workers at the Pathfinder Dam lay the first stone in 1906. (Courtesy Casper College Western History Center)
  • Construction of the Pathfinder Dam on the North Platte River southwest of Casper. It was completed in 1909.
    Construction of the Pathfinder Dam on the North Platte River southwest of Casper. It was completed in 1909. (Courtesy Casper College Western History Center, Chuck Morrison Collection)
  • A photo showing the Pathfinder Dam after completion. The dam is operated by the U.S. Bureau of Reclamation and was constructed for the North Platte Project of irrigation.
    A photo showing the Pathfinder Dam after completion. The dam is operated by the U.S. Bureau of Reclamation and was constructed for the North Platte Project of irrigation. (Courtesy Casper College Western History Center, Chuck Morrison Collection)
  • The North Platte River just below the site for the Pathfinder Dam in 1904.
    The North Platte River just below the site for the Pathfinder Dam in 1904. (Courtesy Casper College Western History Center)

Pathfinder Dam

Williams said the Bureau of Reclamation was created in 1902 by the Reclamation Act for the express purpose of developing irrigation projects in the Western United States. The 214-foot-tall Pathfinder Dam, 47 miles southwest of Casper, became its early success story. It was also a building block for other dams and canals built in the years that followed.

Operating the system today involves projecting snowmelt and ensuring water deliveries, but in the early days there were lessons to be learned.

As the first dam on the North Platte project, Pathfinder, completed in 1909, stored water from the spring mountain snowmelt in southern Wyoming and northern Colorado and delivered it downstream to irrigation projects that were constructed in southern Wyoming in the Torrington area and near Scottsbluff, Nebraska.

The water from the dam was for both Interstate Canal and Fort Laramie Canal that diverged from the North Platte in Guernsey, Wyoming, toward Nebraska, and southern Wyoming.

“Both of those canals deliver water to a combined over 200,000 acres of land in Wyoming and Nebraska,” Williams said. “Although there were irrigation canals that were already in place, they entered into contracts with the Bureau of Reclamation to also receive from Pathfinder Dam.”

Guernsey Dam And Others

Williams said the Pathfinder Dam did not have a hydroelectric component. As the Bureau of Reclamation evaluated needs as the 20th century progressed, it saw the need to build a dam closer to the water delivery area in southeastern Wyoming. The Guernsey Dam was completed in 1927.

“Because this was a federal project, it didn’t matter if the delivery area was in Wyoming or Nebraska,” Williams said.

The Guernsey Dam also was built as a means to produce power.

In the 1930s, new lands were identified for irrigation needs in the Casper region and the Bureau of Reclamation built two additional dams on the North Platte River as part of the Kendrick Project.

The Seminoe Dam was built about 40 miles upstream from Pathfinder on the North Platte River and opened in 1939. The Alcova Dam, in Alcova, opened in 1938, was built primarily as a diversion dam for the Casper region. Both Seminoe and Alcova dams generate hydroelectric power.

“The intent of Alcova was to raise the water level of the river about 160 feet so the water could flow into the canal that was being built to basically flow by gravity all the way from Alcova to deliver irrigation water to lands near Casper,” Williams said.

And for Casper-Alcova Irrigation District Manager Joan McGraw, that system provides irrigation water for 24,000 acres of land and the needs of 550 farmers, ranchers and landowners in her region.

“If that project didn’t exist, there would be no farming out there,” she said.

The bureau then built another dam downstream from Seminoe, Kortes Dam, used for hydroelectric power generation.

“Pathfinder would deliver water downstream for irrigation in May through September and then irrigation was finished, and they would basically close the gates at Pathfinder so all the water coming in during the fall and winter could be ready to deliver water out again in the spring,” Williams said. “So that pretty much shut the river off at Pathfinder. After Alcova was built, there would be some water in Alcova but they would shut the gates at Alcova, and there would be very little water making its way down the river.”

  • A series of dam and irrigtion project put in motion 120 years ago continue to be the lifeblood for centeral and eastern Wyoming farmers and ranchers.
    A series of dam and irrigtion project put in motion 120 years ago continue to be the lifeblood for centeral and eastern Wyoming farmers and ranchers. (Stuckreed via adobestock.com)
  • An illustrtion of irrigtion downriver from the Pathfinder Dam.
    An illustrtion of irrigtion downriver from the Pathfinder Dam. (Cowboy State Daily Staff)
  • Seminoe Dam is another of the Wyoming dams that have brought water to eastern and central Wyoming.
    Seminoe Dam is another of the Wyoming dams that have brought water to eastern and central Wyoming. (Bureau of Reclamation)
  • The Pathfinder Reservoir and dam provided the first step in the irrigation system for the North Platte Project run by the Bureau of Reclamation.
    The Pathfinder Reservoir and dam provided the first step in the irrigation system for the North Platte Project run by the Bureau of Reclamation. (Courtesy Google Earth)
  • The Glendo Reservoir stores water for the irrigation season and allows for the river upstream to maintain a good flow through the winter months and keep water quality high for Casper, Glenrock, and Douglas areas.
    The Glendo Reservoir stores water for the irrigation season and allows for the river upstream to maintain a good flow through the winter months and keep water quality high for Casper, Glenrock, and Douglas areas. (Courtesy Google Earth)
  • A postcard showing the Alcova Dam following its completion. The dam serves to help provide irrigation water to the Casper region.
    A postcard showing the Alcova Dam following its completion. The dam serves to help provide irrigation water to the Casper region. (Courtesy Casper College Western History Center, Chuck Morrison Collection)
  • Courtesy Google Earth
    Courtesy Google Earth (Dale Killingbeck, Cowboy State Daily)
  • La Prele Dam DA Smith Drilling Co 11 10 23
    (DA Smith Drilling Co.)

Fixing Winter Flows

The issue of water quality in Casper and downstream areas in the winter led to the creation of the Glendo Reservoir and hydroelectric dam in 1958 near Glendo, Wyoming. Glendo allowed for water release all through the winter from Pathfinder raising water levels and water quality in Casper, while capturing the water at Glendo for release in the spring to Guernsey.

The Gray Reef Reservoir, downstream from Alcova, opened in 1961 as a “regulation reservoir.”

“We can fluctuate the inflows from the power plant up and down during the day and keep the river steady,” Williams said. “That’s what Gray Reef does.”

While the North Platte River has many dams and components to both the North Platte and Kendrick projects, Williams said his office operates it as one system. Water allotments for various water contracts are carefully accounted for even though the contract water may be stored in a different reservoir.

On the Casper Canal, McGraw said users have allotments of metered water that are drawn from the canal. Most of it goes for animal feed crops.

“Mostly hay, grass and alfalfa,” she said. “Some people are growing crops such as corn.”

One dam associated with the LePrele Irrigation District in Douglas, which draws water from the North Platte River, has come under scrutiny in recent years for its deteriorating condition. Water levels associated with the dam’s reservoir were drawn down in 2019. Repeated attempts to reach the LePrele Irrigation District about the dam and current irrigation plans were not successful by deadline.

Dale Killingbeck can be reached at dale@cowboystatedaily.com.

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