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SFS Projects and Best PracticesColorado Irrigators Work to Conserve Water and Energy By Judy Farrell, WAPA "Energy Services Bulletin" The Colorado State Soil Conservation Board's efforts to improve irrigation efficiency have paid off in substantial water and energy savings. There are about 8,500 irrigation permits in the state. Most farm irrigation operations are in the eastern part of Colorado, pumping water from the Ogallala Aquifer. New, highly efficient irrigation systems use much less water to achieve full crop yields. Where it once took a 700-800 gallon-per-minute (2,6493,028 liter-per-minute) well to raise a half-mile-radius circle of corn, now it can be done with less than 500 gallons per minute (1,862 liters per minute).
Farmer Posts Savings A look at a Washington County irrigation operation shows how the conservation program saves energy and costs. Bob Poitz farms 6,000 head of custom feedlot cattle and more than 2,000 acres (809 hectares) of wheat, corn, onions, and beans. In 1989 and 1990, he planted the 1,125-acre (455-hectare) irrigated section of the farm in equal amounts of corn and beans. Also in 1990, after consulting with the Conservation Board, Poitz installed Low-Energy Precision Application nozzles on a onehalfmile radius center-pivot sprinkler system. The LEPA system applies water through lowpressure drop nozzles, allowing more water to reach the ground and reducing evaporation losses. The chemigation mode on the LEPA nozzle also helps the Poitz farm stay within Environmental Protection Agency regulations on chemical application. "The efficiencies on water application went from 68 percent to 93 percent," said Poitz. The first year, the LEPA system saved 146.2 acrefeet (59.1 hectare-meters) of water and 181,600 kilowatthours of energy. This saved more than $13,000 in water pumping costs. Poitz now irrigates the section from one 1,900-gallon-per-minute (7,191liter perminute) well instead of two.
700 Systems Use LEPA More than 700 irrigation systems in the state have been converted to the lowpressure drop nozzles since 1989, according to recently retired Board Director Dan Parker. The lower water pressure of 6 pounds per square inch versus 20 psi (2.7 kilograms per square centimeter versus 9 kilograms per square centimeter) uses less energy. About 90-95 percent of the water reaches the crop's root zone, compared with 65-70 percent with pivot irrigation systems. Delivery of the water low to the ground in a smaller area, similar to flood irrigation, wets only the crop. There is much less evaporation. Irrigators can also better manage use of water by slowing the sprinkler system at the pivot. Instead of applying three quarters of an inch of water every 35 days, it is more efficient to apply 23 inches to the soil profile every 10-14 days.
Other Ways to Save The LEPA technology is only one of several ways irrigators can conserve water and energy. Other methods include:
As changes occur to the water supply, irrigators can save money through pump testing and corrective measures. Many pumps in use today were sized for quantities of water that may no longer be available. Since 1986, the Conservation Board has tested between 300-350 irrigation pumps per year, Parker said. The pump test evaluates condition of the pump, water pressure developed in the system, and the amount of water delivered to the field. Testing also shows if a well is operated at too great a discharge rate for the existing pump and well conditions. Testing further determines whether the irrigator can save energy by adjusting, rebuilding, or replacing the existing pump, drive systems, or power unit. Improving performance of an average pumping plant can save up to 30 percent of irrigation energy costs.
Surge Saves Water For furrow irrigation operations, surge irrigation is an effective water management tool. Surge techniques can save up to onethird of the water needed for good crop yields. Conservation results from reducing the deep percolation of conventional furrow irrigation where the water seeps below the crop's root zone. Developed in the desert climate of Israel, surge systems propel pulses of water down the furrow row from the main feeder pipe. The irrigation cycle is alternated between two sets of furrows. Valves operated by programmed photocells control the release of water. Irrigators who have experimented with surge irrigation report significant reduction in tailwater, the extra water needed to irrigate the far end of the furrow. Surge irrigation provides a more even penetration of water over the length of a field, preventing leaching of pesticides and fertilizers through the soil profile. The Conservation Board teaches irrigators to assess the effectiveness of irrigation and prevent overwatering by monitoring moisture at various soil depths, said Parker. Gypsum blocks, which conduct electricity based on the level of moisture in the soil, are planted at one, two, and threefoot levels. The blocks are connected to a meter that records the current flow of the block at each depth. Measuring soil moisture enables many irrigators to shorten their watering seasons. Where they once irrigated from midMay until September, now they are watering for only two months. The agency also works with irrigators to solve problems of compacted soils and manage crop residue to take greater advantage of "free" water from rain and snow. For more information, call Conrad Bauer at (970) 332-3173.
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