“SMART” Controllers and Sensors: Critical Components of Automated Irrigation Systems.

 

 

“SMART” Sensors and Controllers- Optimizing Water Use Efficiency.Diganta D. Adhikari, Dave Goorahoo, Florence Cassel S and David Zoldoske

 

According to the California Water Plan Update 2005, Californians used about 2.9 million acre feet of water to irrigate landscape, parks and golf courses. The potential for water conservation in the landscape ranges from 400,000 to 600,000 acre feet per year through improved hardware design and management. One approach of achieving this goal is to use “SMART” controllers and sensors as part of a Feedback loop irrigation system to deliver water on “DEMAND” based on plant water requirements.

In collaboration with the Irrigation Association (IA) and water purveyors, the Center for Irrigation Technology (CIT) has been conducting research aimed at improving residential irrigation water use efficiency. First, we review research on developing standards and protocols to evaluate the accuracy, reliability and repeatability of commercially available soil moisture sensors under various salinity, soil types and temperature conditions. Then, we discuss potential opportunities for applied research which make these data available in real time on the web, so that monitoring and control can be done remotely via PDA’s/Laptop or cell phones.The accuracy and reliability of soil moisture sensors evaluated to date appear to be dependent on soil textural classes. For example, a Time Domain Transmissitivity (TDT) based sensor had high correlation (r² = 0.89 to 0.99), between measured and predicted moisture water contents measured for various temperatures and salinity levels in medium and coarse textured soils.  Also, the use of soil moisture sensors or Evapotranspiration (ET) based controllers with feedback loop has the potential to give the end users better control over irrigation management as water was applied only when needed. For example, a system has been designed to prevent freeze damage in citrus crops by incorporating the micro- sprinklers within the crop canopy using a Supervisory Control and Data Acquisition (SCADA) system.