Importance of ET Controller Program Settings on Water Conservation Potential

In unincorporated Orange County, Florida, 57% to 62% of single-family residential homes were found to regularly over-irrigate, resulting in the need to find better ways to schedule automatic irrigation. The objective of this research was to evaluate the effects of programming for identical virtual landscapes to further explore the water savings potential of evapotranspiration (ET) controllers. As a virtual test, three Rain Bird ET controllers were studied: the ESP-SMT controller with two firmware options (original and an updated), and the ESP-SMTe, a replacement product for the ESP-SMT. Irrigation was scheduled for a virtual central Florida landscape by altering possible program settings of plant type, microclimate, soil type, and density that relate directly to parameters used in the soil water balance. The ESP-SMTe consistently applied similar amounts of irrigation to the ESP-SMT with updated firmware, indicating that controller updates were minor between the two models. The settings were optimized for Florida landscapes by selecting a heavier soil type, increasing the shade, and selecting a medium stand for a custom plant type, resulting in reductions in irrigation application. The ESP-SMTe and ESP-SMT with updated firmware were different from the ESP-SMT with original firmware, where newer models applied more water despite identical settings, averaging 12 to 21 mm more per month than the original firmware. Additionally, all of the controllers were unable to fully account for rainfall throughout the test resulting in a minimum of 51% in over-irrigation compared to the gross irrigation requirement (GIR). Increasing the accuracy of rainfall accounting would be extremely beneficial to overall water conservation and efficiency. In a separate, independent ET controller study, there was a large discrepancy in irrigation application among multiple brands programmed to irrigate the same virtual landscape. This further shows the importance of understanding the algorithms behind the program settings.

[1]  Michael D. Dukes,et al.  Irrigation scheduling performance by evapotranspiration-based controllers , 2010 .

[2]  Michael D. Dukes,et al.  Bahiagrass crop coefficients from eddy correlation measurements in central Florida , 2009, Irrigation Science.

[3]  Melissa B. Haley,et al.  Residential Irrigation Water Use in Central Florida , 2007 .

[4]  Michael D. Dukes,et al.  Water conservation potential of smart irrigation controllers on St. Augustinegrass , 2009 .

[5]  Michael D. Dukes,et al.  Landscape irrigation scheduling efficiency and adequacy by various control technologies , 2011 .

[6]  Richard G. Allen,et al.  Using the FAO-56 dual crop coefficient method over an irrigated region as part of an evapotranspiration intercomparison study. , 2000 .

[7]  I. A. Walter,et al.  The ASCE standardized reference evapotranspiration equation , 2005 .

[8]  Michael D. Dukes,et al.  Landscape irrigation by evapotranspiration-based irrigation controllers under dry conditions in Southwest Florida. , 2009 .

[9]  Michael D. Dukes,et al.  Implementing Smart Controllers on Single-Family Homes with Excessive Irrigation , 2015 .

[10]  Michael D. Dukes,et al.  Soil Moisture Sensor Landscape Irrigation Controllers: A Review of Multi-Study Results and Future Implications , 2012 .

[11]  L. S. Pereira,et al.  Crop evapotranspiration : guidelines for computing crop water requirements , 1998 .

[12]  Witold F. Krajewski,et al.  Sampling Errors of Tipping-Bucket Rain Gauge Measurements , 2001 .

[13]  Michael D. Dukes,et al.  Estimation and Analysis of Irrigation in Single-Family Homes in Central Florida , 2014 .

[14]  D. A. Devitt,et al.  Residential Water Savings Associated with Satellite-Based ET Irrigation Controllers , 2008 .

[15]  Michael D. Dukes,et al.  Water Conservation Potential of Landscape Irrigation Smart Controllers , 2012 .

[16]  Grzegorz J. Ciach,et al.  Local Random Errors in Tipping-Bucket Rain Gauge Measurements , 2003 .

[17]  Michael D. Dukes,et al.  Methodologies for Successful Implementation of Smart Irrigation Controllers , 2015 .