Irrigation Systems

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Introduction

Since water pumping accounts for more than 30% of California's total on-farm energy use, achieving irrigation energy efficiency and conserving water is a top priority for farmers seeking to enhance a farm's profitability by saving both water and energy. Certain farms in California's Central Valley have saved 25% in electricity, fertilizer and herbicide costs through irrigation systems efficiency measures.

Technology Options

Proper design of an irrigation system requires that the pumping system precisely match to the irrigation distribution system so that the pressure and flow rate required can be efficiently provided by the pumping system. The energy required to pump water is determined by the total dynamic head (water lift, pipe friction, system pressure, etc.), the water flow rate desired and the pumping system's efficiency.

To improve overall pumping plant efficiency, first test your well pumps. Check with your utility or water agency for free and low-cost pump tests. Here are some general guidelines and energy saving tips for on-farm irrigation systems:

  • Pumps between 55% and 60% efficiency: Consider adjusting impeller.
  • Pumps between 50% and 55% efficiency: Consider adjusting impeller first; consider repairing or replacing pump if adjusting impeller has no effect on efficiency.
  • Pumps with less than 50% efficiency: Consider repairing or replacing.
  • When replacing standard motors, buy new energy-efficient electric motors.
  • Reduce the total dynamic head of pumps (power consumption) by installing variable speed drive (VSD) controllers. These systems work best in Time of Use rate schedules on deep wells with frequent start-ups.
  • Use energy-efficient water-conserving irrigation practices. Adopt irrigation scheduling methods and deficit irrigation practices to conserve water.
  • Sign up for Time of Use rate schedules with your utility company, which can reduce total costs as well as possibly avoid power interruptions.
  • Calculate if your current pump and irrigation system can deliver the water your crops need in 18 rather than 24 hours.

Additional opportunities for energy savings:

  • A flap gate is a simple, inexpensive hydraulic gate for automatic upstream water level control, supporting water conservation and efficiency.
  • Doppler technology has been developed for advanced water flow measurement technology that is relatively easy to use, applicable to various hydraulic conditions and very accurate.
  • Micro-irrigation systems reduce the amount of energy and water required to irrigate an area of land, compared to other irrigation systems. Micro-irrigation systems place most of the irrigation water where it can be used by the crop to reduce the amount of water that needs to be pumped through the irrigation system to supply the entire crop water needs.
  • Center-pivot irrigation systems are the leading method of crop irrigation in many agricultural zones across the United States. Using this energy-efficient irrigation system, water can be pre-programmed to shut off in areas of the field that are non-productive, such as rocky outcrops, roads, or streams. Likewise, additional water or fertilizer can be applied to meet the specific nutrient or water needs of a crop.



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Efficiency Benefits

Efficient irrigation systems allow growers to use energy more efficiently, contribute to a decline in plant disease problems, and improve the efficient use of chemical fertilizer. Vegetable growers are saving upwards of 25% in water pumping, fertilizer and herbicide costs by using subsurface drip irrigation technologies in the Central Coast Region of California.

With non-uniform irrigation systems, if sufficient water is applied at each irrigation to assure that none of the crop is under-irrigated, most portions are over-irrigated. This increases the waste of water and chemicals. Also, the fuel required to pump excess water and to produce and inject excess chemicals are wasted.

Even well-designed irrigation systems do not apply water with perfect uniformity. The cost of obtaining perfect uniformity is prohibitive. Rather, the optimum design requires that the value of the natural resources wasted be balanced by the increased cost of achieving a greater degree of uniformity of water application, including the increased value of agricultural products that would be required to pay for the increased irrigation system cost.

Improved water-use efficiency creates energy savings because less energy is used to pump water. And, at 33,000 British thermal units (Btu) of primary energy per pound of nitrogen fertilizer, the efficient use of fertilizer saves energy, too.

Manufacturers

Manufacturers and distributors of energy-efficient farm irrigation equipment include:

The Irrigation Association, a North American nonprofit, offers a directory for locating state-of-the-art irrigation product information.

Purchasing Tips

If you need to make changes to the pump and/or the irrigation system, calculate the cost and determine how to implement the project. Talk with the utility company about financing options. Considerations include:

  • Irrigation system selection, design, operation and management
  • Irrigation pumping plant design, installation and efficiency testing
  • Proper installation of flow meters, weirs and other flow measurement devices
  • ET (evapotranspiration) for determining crop water requirements
  • Irrigation scheduling based on soil moisture, plant indicators and other methods
  • Wastewater reuse

Emerging Technology

Precision farming has driven new and emerging technology advances. Existing technology includes micro-irrigation and center-pivot systems. Emerging technology includes the use of a geographical information system (GIS), global positioning satellite (GPS) data and infrared thermography. Infrared thermography is the use of infrared radiation to qualitatively and quantitatively express heat signatures and heat differences.

For more information on advancing irrigation and farm technology, consult resources such as:

  • Irrigation Training and Research Center at California Polytechnic State University in San Luis Obispo
  • EnergyAg NewsBriefs, a bi-monthly listserv that highlights selected articles on latest energy/agriculture technology, programs and activity. To subscribe, send a blank message to: subscribe-Energy_Ag-NewsBriefs@listserv.energy.wsu.edu