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Under Pressure

When it comes to irrigation, there is no place like Nebraska. By the time the 2007 United States Department of Agriculture (USDA) Farm and Ranch Irrigation Survey was conducted, Nebraska overtook California as the state with the largest number of irrigated acres and has held the title ever since.

Before our state was founded, Nebraska farmers had started our incredible irrigation history. When Nebraska joined the United States on March 1, 1867, about 10,000 acres of crops were already irrigated with surface water from ponds, lakes and rivers. By 1950, irrigated coverage increased more than 100-fold due to the rapidly expanding use of ground water. However, a revolutionary new water delivery system would help drive Nebraska to more than 8 million irrigated acres by the end of the century: the center pivot.

Traditional delivery systems used high-volume, low-pressure pumps to draw from water sources, then relied on gravity to distribute water through canals, pipes, siphon tubes and crop rows. Sadly, about half of the water using this method ran off fields, percolated down through the soil or evaporated before plants could utilize it. Center pivots keep the pumped water contained until it is released in close proximity of the plants being watered. Some center pivot systems deliver water so efficiently, 95% or more is utilized by the crop. Today, nearly 90% of Nebraska’s irrigated ground is watered with approximately 60,000 center pivots.

Converting to center pivot irrigation systems has provided farmers significant effort, time and water savings while increasing crop yields. Unfortunately, there have been many missed opportunities to optimize energy efficiency in doing so. While traditional systems were designed for high flow/low pressure operation, pivot systems require less flow but much higher pressure to deliver uniform water distribution. When converting, it was common to forego the additional cost of replacing the original pump with one designed to match the new pivot’s flow and pressure requirements. Many farmers have opted to modify existing pumps by installing inexpensive valves and regulators.  Some chose to replace their old pump at the same time, but may have selected a new pump that oversized delivery pressure. Still others selected pivots with sprinkler packages that provided wetting diameters larger than necessary to eliminate runoff concerns. This too, requires more pressure than necessary, which results in greater energy consumption.

The 2018 USDA Farm and Ranch Irrigation Survey indicated that one in eight irrigation wells in Nebraska operate above 60 pounds per square inch (psi). While a handful have operating conditions that can only be addressed by higher pumping pressure, many could find significant energy savings through system improvements.

The table below illustrates the operation of a center pivot system with average overall efficiency that spans 135 acres. Over the course of a season, 10 acre/inches of water are pumped with an average lift of 138 feet and a flow rate of 760 gallons per minute. A system designed to operate at 45 psi will require about 16% less energy than one designed for 65 psi.

Though many ag producers have seen considerable cost savings and enhanced performance by reducing operating pressure of their entire system, many others may still be using more energy or pumping more water than needed.

If your your local electric utility offers incentives, you may be eligible for one of the EnergyWiseSM agricultural operations. All-electric irrigation systems as well as other electricity-saving improvements around the farm bring value to producers, as well as power providers. Contact your local electric utility to learn more.

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