Development of an on-time logger for irrigation systems

An inexpensive micro-processor and pressure switch ($125) were developed by Washington State University’s (WSU) Irrigated Agriculture Research and Extension Center (IAREC) to log the on-times of irrigation systems. The purpose of the on-time logger was to provide better information on how irrigators respond to new irrigation management techniques and to document the water/electricity savings from improved “on-farm” irrigation practices. This on-time logger was tested by installing two loggers each at two on-farm sites where irrigation controllers opened valves for predetermined operation times. At the Prosser test site, both loggers monitored the controller-designated operation times with an average ratio of 1.0 (logger on-time to controller operation time). However, at the Outlook site, both loggers recorded on-times longer than the controller operation time with ratios of 1.1 and 1.24. At the Outlook site, the loggers were located at the end of irrigation laterals that were located at the bottom of a steep hill. In addition, the sprinkler heads were located on tall risers for apple cooling. Therefore, the pressure switches did not open immediately after the zone valves were closed because water in the pipes kept pressure on the switch until sufficient drainage could occur. On-time loggers can be successfully used to monitor the impact of on-farm irrigation improvements, but care needs to be taken to set the switch tripping pressure in accordance with the irrigation system’s configuration.