Ranchers living in the mountainous areas of Colorado, Idaho, Utah and beyond are turning to Mother Nature to power their center-pivot irrigation systems instead of relying on expensive diesel or electricity.

The use of hydromechanical systems to power pivots is also allowing some ranchers to convert from flood irrigation to sprinkler systems, which is boosting grass and alfalfa yields while cutting down on water usage and impacts to the environment.

“If you have the right situation, hydromechanical systems could work very well for your operation,” says Vance Fulton, an engineering technician with the USDA’s Natural Resources Conservation Service in Steamboat Springs, Colo. “Some of the ranchers I’ve worked with are saving approximately $2,000 in annual energy costs per pivot, and the expected payback time to install such systems can be as low as three to five years.”

For a hydromechanical pivot system to work, a big change in elevation over a relatively short distance is needed, says Fulton, noting that hay pastures in mountainous valleys or tucked below hillsides are conducive to such installations.

“Some ranchers have submitted applications to our local NRCS, which can help with design services for these types of systems. They can work well in areas where sufficient water pressure can be generated using at least 100 to 150 feet of fall,” Fulton says.

“No pumps, motors or electrical connections are required, resulting in very low annual operational expenses and minimal maintenance,” he notes. “Because hydromechanical systems do not produce electricity, such projects are not regulated by the Federal Energy Regulatory Commission.”

A hydromechanical system uses the power of water rushing through a pipeline to directly drive and pressurize the center pivot, which eliminates the need for electricity or diesel, Fulton explains.

Pipeline pressure based on gravity
One system installed on the Bear River Ranch in northwest Colorado near Steamboat Springs uses 560 gallons of water per minute in combination with 126 feet of “head.” The latter term is used to describe the vertical change in elevation between the head water level (for example, a reservoir or irrigation ditch) and the tail water (in this case, the hydromechanical system).

“Building pressure in the pipeline is solely based on gravity, and under the right conditions, you can generate a tremendous amount of pressure,” says Fulton, noting that the combination of head and water in the Bear River Ranch pipeline system produces the equivalent of 5.2 kilowatts of power, which is enough to drive the pivot.

The total cost of the turbine and related infrastructure was $13,000. Of that, NRCS provided a cost-share of $6,000 (this doesn’t include the cost of the pivot or pipeline).

Fulton says the NRCS supports such projects, in part, because they cut down on water usage compared to flood irrigation, and they are much more environmentally friendly.

“A couple of the ranches I’ve worked with were using flood irrigation. On the uneven terrain, it was notoriously inefficient. High areas weren’t getting enough water, and low areas were getting too much,” Fulton says. “With the center pivot, they are now getting better yields of grass hay with less water.”

MISSION ACCOMPLISHED: Gary Clyncke, red shirt, and NRCS employee Osman Shitu inspect a new hydromechanical center-pivot system on Clyncke’s Bear River Ranch in northwest Colorado. Water rushing down a pipeline through a turbine (the blue part in the center) powers the center pivot.

Additionally, he emphasizes, “In mountainous areas, open ditches that provide water for flood irrigation can create serious erosion problems. You can get some really bad gullies forming when trying to get water down steep hillsides.”

Also, flood-irrigated fields potentially lead to soil, fertilizers and herbicides being carried into waterways.

Fulton says a couple of the ranchers he assisted buy reservoir water, and rates increased sharply several years ago.

“That drove them to look at how they could use water much more efficiently, while at the same time trying to increase hay yields,” he says, adding that the hydropowered pivots helped them to achieve those goals.

Fulton says there are other pluses, too. “Typically, pivots either run off the electric grid or diesel, and that can get expensive — but the operating costs of using hydropower can be very low.”

Hydraulic pivots and hydropower
Hydraulically driven center pivots are well suited for hydromechanical-powered pivot systems, says Fulton.

“Hydraulic motors lend themselves particularly well to hydromechanical systems, as opposed to hydroelectric systems,” he says.

Fulton emphasizes that hydromechanical pivot systems are not generating electricity. Instead, water flowing down a pipeline builds up enough pressure to drive the pivot.

“It’s a very simple system, because water pressure spins a turbine, which provides energy for the hydraulic motor on the pivot,” he says.

Fulton says the biggest single cost for such systems is typically the pipeline.

“Since we’re dealing with very high pressure, burying the pipeline helps to hold it in place, and it also helps to protect the pipe from damage,” he says. “Safety is a big factor, and a minimum of 30 inches of burial is necessary.” Despite the pipeline being buried, everything needs to be drained prior to winter to avoid cracks.

With cost-share assistance from NRCS, such systems have a good payback time (as low as three years) when taking into account the cost of electricity and diesel.

“Center-pivot machinery and the turbine are generally given a useful lifetime of 20 years, but that can be much longer with proper maintenance and operation. Care must be taken to filter water prior to its entry into the system. The cleaner the water, the better,” says Fulton, noting that the construction of a gravel infiltration gallery where water enters the pipeline is among the steps that can be taken.

There are other bonuses when converting to center-pivot systems, including higher hay yields and potentially higher-quality forage.

“Ranchers who manage their hydromechanical systems properly are reporting few problems, and they are also getting higher crop yields using less water than historically have been achieved with flood irrigation,” Fulton says.

“A hydromechanical system allows us to kill several birds with one stone.”

Waggener writes from Laramie, Wyo.