Water Savings Associated with Evapotranspiration-Based Irrigation Scheduling.

Water Savings Associated with Evapotranspiration-Based Irrigation Scheduling

Landscape water conservation is an important issue for municipalities throughout the Western United States, and especially in Utah as rapid growth strains existing water supplies. Improving irrigation efficiency is an important goal for municipalities, but renovations are costly. In an effort to reduce landscape water use and justify future irrigation upgrades, the Central Iron County Water Conservancy District funded three renovation projects at municipal sites (6.28 acres of turf) in Cedar City, Utah. These three sites were equipped with an evapotranspiration-based (ET) irrigation controller, main line flow sensor, on site weather station, and rain sensor. The objectives of this project were to: (1) quantify the water saving capability of Weathermatic’s SmartLine irrigation controller (2) estimate payback period (3) gauge employee acceptance and usage of the controller’s web interface. Irrigation adequacy and scheduling efficiency were calculated at 30-day intervals that coordinated with the water meter reading to determine the amount of over- or under-irrigation. The project took place between August 2013 and October 2016. All sites were over-irrigation prior to renovations. Scheduling efficiency (measure of over-irrigation) decreased at all sites, ranging from 41%-67% average reduction over the three-year project time frame when compared to scheduling efficiency in the three years prior to project inception. At two of the sites, water savings were the result of more accurate irrigation scheduling relative to environmental demand vs. deficit irrigation at the expense of the turf quality and overall health. With commercial water rates at $1.00 per thousand gallons, the payback period was less than 2.5 years. Employees adapted to the new technology but not without growing pains. Many hours were spent preforming water audits, training employees, installing equipment, and making system adjustments during the first growing season. Overall, the system showed measurable savings and a relative short payback period, but time must be spent on employee trainings and proper programing of the controller in order to maintain acceptable turfgrass quality and show good scheduling efficiency and irrigation adequacy.