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OPPORTUNITIES TO MAXIMIZE THE UTILIZATION OF WATER BY IRRIGATORSSignificant improvement has been and continues to be made in irrigation equipment, design, performance efficiency and grower management. Advancements in irrigation technology provides irrigators more timely information more expediently to manage irrigation systems and groundwater and to utilize rainfall. IRRIGATION SYSTEMS Extensive research and field tests show that water application efficiency with LEPA center pivots (both the bubble and double ended sock) and subsurface drip systems is approximately 98 percent, with appropriate planning, preparation and management. Examples of growers' success are 100 pounds of cotton lint and 600 pounds of corn or more per inch of annual irrigation. These are measures of achievable efficiencies for comparison. Low pressure center pivots equipped with spray or similar heads spaced 60 or 80 inches apart and positioned eight to 16 inches above ground level typically average 86 to 90 percent water application efficiency. Energy efficiency is similar to LEPA and drip systems. Significant acreage is now irrigated with these higher efficiency systems. Over crop application efficiency with center pivots has been measured to average 75 to 80 percent. Surge valves typically improve furrow irrigation efficiency an average of 10 to 40 percent. Depending on soil type, land slope, length of run and management. Surge irrigation is inexpensive to adopt in relation to the benefits of more uniform water distribution, reduced deep percolation, reduced to no tailwater, and less total irrigation. Many surge valves are used to improve irrigation efficiency. Some growers have cut irrigation amounts by 50 percent. Field measurements show that furrow irrigation is improved an average of 15 to 20 percent from the appropriate use and management of tailwater recovery systems. Tailwater recovery pits and recirculation pumps have been used since the 1960's to conserve and manage groundwater. Typically, there is one recovery system for each section of land. Underground pipelines improve irrigation efficiency an average of 15 to 20 percent, depending primarily on soil type and management. Irrigation pipelines are used extensively to conserve groundwater. An economical, short life surface polyethylene pipe has been used in recent years where underground pipelines have not been installed to gain similar efficiency. APPLICATION EFFICIENCY vs. IRRIGATION SYSTEMS
96-98% - Drip Irrigation MANAGEMENT TOOLS Soil moisture sensors have been used since the 1970's as tools to improve irrigation management and scheduling and utilize rainfall. Soil moisture sensors and other devices are used to manage irrigation by many irrigators. The South Plains potential evapotranspiration (PET) network initiated in 1992 provides predicted daily crop water use utilizing automated weather stations accessed by a personal computer in Lubbock. A similar PET network (North Plains-Amarillo) that will include 10 or more strategically located automated weather stations is expected to be operational for the '95 crop season. The networks provide growers and crop consultants irrigation management and scheduling information as influenced by climatic conditions the previous day. Some crop consultants have their own automated weather stations, too. Deficit high frequency irrigation, especially of cotton, has been researched and is being rapidly adopted. High efficiency LEPA and similar high efficiency center pivots and drip irrigation systems are managed to apply only a portion of the predicted evapotranspiration (PET) calculated by the computerized automated weather station network. Computerized irrigation system control panels compliment the procedure. Flow meters provide accurate information to both design and manage irrigation systems. Flow measurements helps plan acreages of various crops to plant, depending on water use characteristics and seasonal requirements. They are used to monitor irrigation wells and pump performance. Irrigation pumping plant efficiency tests are made to identify pump and power unit performance and efficiency to manage irrigation costs. Written and oral educational information is used to improve irrigation management technology, skills and to evaluate economics. TILLAGE Field measurements show that furrow dikes retain 10 to 15 percent more of average rainfall than undiked fields. Also, they hold water applied by center pivot systems within the appropriate vicinity of plants. Conservation tillage utilizes both less plowing and crop residue to contain rainfall, snow and irrigation water in the appropriate uniform location and to conserve existing soil moisture. Ridge till farming where furrows and beds remain in place for consecutive crop years is also being evaluated and adopted. This practice conserves soil moisture, rainfall and groundwater. Planting rows in a circle where center pivots are used helps maintain water where it is applied, provides uniform crop irrigation and prevents runoff. More rainfall is usually maintained too. Contour rows and terraces are utilized on some farms, especially where land slope is greater to control both irrigation and rainfall. ALTERNATIVE SOURCES Water when available is pumped from 15 to 20 percent of the 19,000 playa lakes that are in the area. Some have been modified to conveniently accommodate the rise and fall of the water level from or the lack of rainfall. Pumping costs are economical. The Santa Rosa aquifer contains moderate quality water for irrigation in some counties. Mixed appropriately with water from the Ogallala aquifer extends the acceptable use. Some water in the Santa Rosa aquifer contains greater salt levels than are acceptable for irrigation.
Leon New
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