Both uniformity and pump/well testing should be performed on an irrigation system every 2-3 years to uncover maintenance issues that can save energy and improve the water application efficiency.
- Uniformity Testing
Uniformity testing is a troubleshooting procedure to check that the water distributed by the irrigation system is being applied uniformly to the field within practical limitations. The test procedure only measures the amount of water applied to the soil surface and is not intended to indicate the amount of water that infiltrated the soil into the root zone. Evaporation, runoff and leaching could all affect the amount of water available to plants in the root zone. A low coefficient of uniformity could lead to plant stress and disease issues because of a water deficit or too much water in different sections of the field despite the average application rate being acceptable.The goal for the coefficient of uniformity is greater than 90%. This test functions as low cost insurance to determine if the nozzles and sprinklers are applying water evenly.The test will take 1 or 2 people about 4 hours to complete depending on the size of the field. It is recommended that a uniformity test be performed every 3-5 years depending on usage and water quality. The University of Wisconsin has test kits that can be borrowed by Wisconsin growers and that contain all the equipment normally needed to check a quarter section straight center pivot system. Transportation of the kit is the responsibility of the grower. Kits are housed in 3 plastic totes, each about 2.5′ long x 2′ wide x 2′ deep.One kit is located at Hancock Agricultural Research Station, Hancock, WI, and can be reserved by contacting the station at 715.249.5961. A second kit is located at the Chippewa County UW Extension office, Chippewa Falls WI, and can be reserved by contacting Jerry Clark at the office at 715.726.7950. A third kit is available from Scott Sanford at the University of Wisconsin-Madison Department of Biological Systems Engineering, and can be reserved by contacting Scott at 608.262.5062, or firstname.lastname@example.org.
- Pump/Well Testing
Pump testing is typically done in an open discharge method where the pump is disconnected from the irrigation system and a flow meter, pressure indicator an valve is installed on the pump output. The pump is started and the valve partially closed until the design system pressure is reached. The system is allowed to run for a period of time, generally 15 minutes, and then the valve is opened and closed to obtain enough points to draw a pressure/flow curve. The static water level should be recorded as well as the water level at each flow point. The net positive suction pressure of the pump should be determined to ensure that the pump is deep enough in the well to prevent cavitation from a lack of water. Irrigation contractors or well drillers generally provide this type of testing service at a cost. The list of equipment suppliers here can help with testing. It is recommended that pumps and wells be tested every 2 years.
More resources on Irrigation System Testing
Below are more resources on testing irrigation systems and pumps. Click on the title of each publication or resource to go to the link and read or download the information.
- Care and Maintenance of Irrigation Wells, by T. Scherer, North Dakota State University Extension publication AE-97.
- Irrigation Pumping Plant Efficiency, by J. Chávez, D. Reich, J Loftis and D. Miles, Colorado State University Extension publication 4.712.
- Technical Irrigation Pumping Plant Test Procedure Manual, by M. Schroeder and P. Fischbach, University of Nebraska-Lincoln Extension publication.
- Field Evaluations of Irrigation Systems: Solis Set or Portable Sprinkler System, by A Smajstrla, B. Boman, G. Clark, D. Haman, D Pitts, and F Zazueta, University of Florida Extension Bulletin 266.
- Irrigation Efficiency and Uniformity, and Crop Water Use Efficiency, by S. Irmak, L. Odhiambo, W. Kranz and D. Eisenhauer, University of Nebraska-Lincoln Extension publication EC 732.