acceptable levels for irrigation adequacy and scheduling efficiency are 80% and 95%,
respectively, SWAT scores for the Florida controllers exceeded those thresholds during only a
few periods. A maximum of 10% of scores were passing in any of the three evaluation periods
that experienced frequent rainfall, indicating that many controllers had trouble accounting for
rainfall. SWAT scores predict water savings only when there is a potential for savings because
there was excess irrigation before the ET controller was installed.
2.3.14 Water Conservation Potential of Smart Irrigation Controllers on St.
By M.S. McCready, M.D. Dukes, and G.L. Miller.
Agricultural Water Management, Vol. 96, No. 11, pages 1623–1632.
This research evaluated the effectiveness of ET-based irrigation controllers, soil moisture sensor
(SMS) controllers, and rain sensors based on irrigation applied and turfgrass quality. Testing
took place on St. Augustinegrass during four periods: April 22–June 30, 2006; September 23–
December 15, 2006; May 1–August 31, 2007; and September 1–November 30, 2007. Two
brands of SMS controllers were tested: LawnLogic LL1004 and Acclima Digital TDT RS500,
with individual units set at three different soil moisture thresholds. Mini-Clik rain sensors (RS)
were set at rainfall thresholds of 3 and 6 mm and at three irrigation frequencies (1, 2, and 7 days
per week). Two ET controllers were tested, the Toro Intelli-Sense and the Rain Bird ET
Manager. For comparison, a timer-based treatment provided 2 days of irrigation per week with
no sensor to bypass irrigation. Testing involved 72 plots of turf. All controller programming
reflected settings that might be used in residential or commercial landscapes.
2.3.15 Evaluation of California Weather-Based “Smart” Irrigation Controller
Prepared by P. Mayer, W. DeOreo, M. Hayden, and R. Davis, Aquacraft, Inc.;
E. Caldwell and T. Miller, National Research Center, Inc.; and P.J. Bickel.
Presented to the California DWR by the Metropolitan Water District of
Southern California and the East Bay Municipal Utility District. 277 pages.
The authors evaluated on-site sensor-based controllers and signal-based WBICs at urban
(residential and commercial) landscapes in California. As of the report date, the EPA had filed its
intent to apply the WaterSense label to smart controllers, but had not identified a testing
protocol. The authors discuss water savings by brand of controller, the factors that affect water
savings, and cost-effectiveness. The authors state, "Even the best, most water-efficient controller
cannot make up for poor system design, installation, and maintenance...." Also: "In this study,
41.8% of the study sites increased their irrigation water use after installation of the smart
The authors analyzed controller cost-effectiveness using the average and median water
savings per customer estimated for sites measuring 4,000; 12,000; 25,000; or 150,000 square
feet. Those areas reflect the usual range of residential and non-residential landscapes found in
northern and southern California. The avoided cost of water for the California water agencies in
the study ranged from about $100 to $1,000 per acre-foot.
2.3.16 Evaluation of Sensor-Based Residential Irrigation Water Application on Homes
By M.D. Dukes and M.B. Haley, Univ. of Florida.
*Abstract only, obtained through search of the Irrigation Association
This project aimed to determine whether an automatic residential irrigation system with soil
moisture sensor controllers could reduce irrigation while maintaining turfgrass quality.
Approaches tested were (1) automatic timer-based irrigation set and operated by the participant;
(2) automatic timer with a soil moisture sensor; (3) automatic timer with a rain sensor; and (4)
automatic timer with a rain sensor plus educational materials, including a recommended run-time
schedule. Irrigation water use, quarterly turf quality ratings, and weather data were collected
continuously for 59 homes during 26 months. Both weekly and hourly irrigation water use were
recorded, and the fraction of total household use was calculated. The soil moisture sensor system
provided the largest savings, cumulatively applying 65% less water for irrigation than the timer-
2.3.17 Landscape Irrigation by Evapotranspiration-Based Irrigation Controllers under
Dry Conditions in Southwest Florida
By S.L. Davis, M.D. Dukes, and G.L. Miller.
Agricultural Water Management, Vol. 96, No. 12, pages 1828–1836.
Based on positive water savings reported for ET controllers used in arid climates, the authors
tested three brands of controllers: Toro's Intelli-sense utilizing the WeatherTRAK ET
Everywhere service (Hydropoint Datasystems, Inc.); SL1600 controller with SLW15 weather
monitor (Weathermatic, Inc.); and Smart Controller 100 (ET Water Systems LCC). The
controllers' irrigation applications were evaluated compared to a timer schedule intended to
replicate that of a typical homeowner. Other methods tested were TIME, based on the historical
net irrigation requirement, and RTIME, which was 60% of TIME. Each technique was replicated
four times in a total of 20 plots of St. Augustine grass, each of which was irrigated by one
individual irrigation system. Techniques were compared to each other and to a timer-based
schedule without rain sensor (derived from TIME). The study period, August 2006–November
2007, was dry compared to the 30-year historical average.
2.3.18 Irrigation by Evapotranspiration-Based Irrigation Controllers in Florida
By S.L. Davis, M.D. Dukes, and G.L. Miller.
Presented at the 29th Annual International Irrigation Show, Anaheim, CA.
November 2–4, 2008.
This presentation reported on the same research as described in reference 2.3.18, above. The
study evaluated the ability of three brands of ET-based controllers to schedule irrigation
compared to a timer. Five systems were evaluated: three ET controllers, a timer method set
according to recommendations from the University of Florida Institute of Food and Agricultural
Sciences, and 60% of the first timer-based treatment. The ET controllers provided an average of
35% to 42% water savings compared to a timer schedule without a rain sensor and maintained
acceptable turfgrass quality. Also, potential water savings from using a rain sensor set to a 6 mm
threshold averaged 21% throughout the study.
2.3.19 Effectiveness of Runoff-Reducing Weather-Based Irrigation Controllers
By S.D. Jakubowski, Municipal Water District of Orange County.
Slides presented at WaterSmart ’08 Innovations Conference, Las Vegas, NV.
This study examined the pollution prevention, reduction in urban runoff, and improvement in
water quality, as well as water savings, attributable to WBICs. The author defined a weather-
based irrigation controller (SmarTimer) as a controller that (1) estimates or measures depletion
of available plant soil moisture; (2) replenishes water as needed while minimizing excess
irrigation; and (3) requires minimal human intervention to modify irrigation appropriately
throughout the season. The study, which ran from 2004–2006, used direct, targeted marketing
including a rebate offered to participants. The study spanned three ET zones (coastal, central,
and foothills) and utilized eight brands of WBIC. The study calculated average calendar monthly
usage both pre- and post-retrofit and statistically compared the two periods. Of the 899 single-
family residential water accounts included in the study, 49% saw no significant difference and
51% showed significantly different water usage (64% saved, 36% used more). Participants
realized a net average savings of 35.7 gallons per day (gpd). Of the 323 commercial accounts
included in the study, 59% saw no significant difference; 41% had significantly different water
usage (73% saved, 27% used more); and net savings averaged 460 gpd.
2.3.20 Evaluation of Evapotranspiration-Based and Soil-Moisture-Based Irrigation
Control in Turf
By G. Grabow, A. Vasanth, D. Bowman, R. Huffman, and G. Miller.
Presented at the 2008 World Environmental and Water Resources Congress,
American Society of Civil Engineers, May 12–16, Honolulu, Hawaii. Pages 1-
This study, performed in fall 2006 in Raleigh, NC, compared amounts of water applied and
resulting turf quality for one ET-based irrigation system, two SMS-based systems, and a timer-
controlled schedule. The effect of irrigation frequency also was examined. Turf ET was
estimated using both an atmometer and the Penman-Monteith equation applied to weather data.
This 20-week study showed that on average the add-on SMS system applied the least water,
whereas the ET-based system applied the most. Averaged across all technologies, weekly
irrigation frequencies used the least amount of water, followed by biweekly and then daily
frequencies. All technologies and frequencies maintained minimally acceptable turf quality
throughout most of the study period. During the last month, however, turf quality declined
considerably for both the add-on SMS and the timer-based system. The on-demand sensor-based
system provided the best combination of water use efficiency and turf quality.
2.3.21 Summary of Smart Controller Water Savings Studies: Literature Review of
Water Savings Studies for Weather and Soil Moisture Based Landscape
Irrigation Control Devices
Prepared by the U.S. Department of the Interior, Bureau of Reclamation,
Southern California Area Office, Temecula, CA; and Technical Service
Center Water Resources Planning and Operations Support Group, Denver,
Final Technical Memorandum No. 86-68210-SCAO-01. 21 pages.
This document summarizes results from about 26 studies of water savings achieved for
residential landscapes by weather-based controllers, soil moisture-based controllers, and
controllers based on both weather and soil moisture. The purpose of this summary report was to
document the overall status of emerging controller technologies for weather- and soil moisture-
based landscape irrigation, with the intent of assisting water agencies in their efforts to promote
such technologies. Topics include urban runoff, turf, scheduling, and reported water savings.
Most of the studies reviewed are described elsewhere in this list of resources.
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2.3.22 Pilot Implementation of Smart Timers: Water Conservation, Urban Runoff
Reduction, and Water Quality
By Kennedy/Jenks Consultants.
Prepared for the Municipal Water District of Orange County, K/J project no.
0753001. 130 pages plus appendixes.
This report describes detailed analyses of pre- and post-retrofit data for Smart Timers installed at
323 commercial and 899 residential sites. The project also involved evaluating associated
changes in runoff and water quality. The results for installation of Smart Timers at single-family
residential (SFR) sites were: irrigation water use declined in 33% of SFRs; increased
significantly in 15% to 20% of SFRs; and showed no change in about 50% of SFRs. The results
for installation of Smart Timers at commercial sites were: irrigation water use decreased
significantly in 15% to 30% of the sites. For about 10% to 20% of commercial sites, water
consumption increased after Smart Timers were installed.
2.3.23 Sensor-Based Automation of Irrigation on Bermudagrass, During Wet Weather
By B. Cardenas-Lailhacar, M.D. Dukes, and G.L. Miller.
Journal of Irrigation and Drainage Engineering, March/April 2008, pages 120-
The objectives of this research were to quantify irrigation water use and evaluate differences in
turf quality for (1) timer-based scheduling with and without a rain sensor; (2) a timer-based
schedule compared to a system that uses a soil moisture sensor (SMS); and (3) various
commercially available SMS systems. The experimental area comprised 3.7 m x 3.7 m plots of
common bermudagrass in Gainesville, FL. Monitoring took place from July 20 to December 14,
2004, and from March 25 to August 31, 2005. Four SMS brands were tested, each of which was
scheduled to irrigate one, two, or seven days a week. Because sustained wet weather occurred
during both monitoring periods, there were no sig
niﬁcant differences in turfgrass quality detected
among the plots. The rain sensors applied 34% less water than no rain sensor. The water savings
for three of four SMS brands, compared to no sensor, ranged from 69% to 92%, depending on
2.3.24 Residential Water Savings Associated with Satellite-Based ET Irrigation
By D.A. Devitt, K. Carstensen, and R.L. Morris.
Journal of Irrigation and Drainage Engineering, Vol. 134, No. 74, pages 74–
This study monitored the irrigation water use of 27 residential sites in Las Vegas, NV. The sites,
which had various percentages of turfgrass in mixed landscapes, were monitored to quantify
savings from satellite-based irrigation controllers. Seventeen sites were equipped with ET-based
satellite controllers, and 10, serving as control sites, were retrofitted with non ET-based
controllers. Thirteen of 16 sites equipped with ET-based controllers saved water compared to 4
of 10 control sites.
2.3.25 Expanding Disk Rain Sensor Performance and Potential Irrigation Water
By B. Cardenas-Lailhacar and M.D. Dukes.
Journal of Irrigation and Drainage Engineering, Vol. 134, No. 1, pages 67–73.
This article reports on an experiment performed to: (1) evaluate two types of rain sensors (RS)
for setpoint accuracy, number of irrigation cycles bypassed, and duration of bypass mode; (2)
quantify the amount of water RS could save; and (3) estimate payback period. The authors tested
12 Mini-click and 4 wireless rain-click rain sensor models by Hunter Industries, Inc. The study
was performed in Florida, from March 25 through December 31, 2005, a period when 62% of
days had rainfall. Three rainfall setpoints were established for the Mini-click devices: 3, 13, and
25 mm thresholds. On average, all RS responded close to their setpoints.
2.3.26 Residential Irrigation Water Use in Central Florida
By M.B. Haley, M.D. Dukes, and G.L. Miller.
Journal of Irrigation and Drainage Engineering, September/October 2007,
The first objective of this study was to document irrigation water use on typical residential
landscapes (T1) in the Central Florida ridge region. The second objective was to determine
whether (1) scheduling irrigation by setting controllers based on historical ET (T2) and (2)
reducing the percentage of turf area along with setting the controllers based on historical ET (T3)
would reduce irrigation water use. This study lasted 30 months beginning in January 2003. The
average T1 or T2 irrigated landscape contained approximately 75% turfgrass (60% to 88%
range). The T3 landscapes averaged 31% (5% to 66% range) turfgrass. The rest of the
landscaped area contained Florida native plants or low-water-use species.
Irrigation accounted for 64% of residential water use for all homes during the study. T1
irrigation averaged 74% of total water use, T2 averaged 66%, and T3 averaged 51%. Average
monthly water use at T2 homes was 105 mm per month, 30% less than at T1 homes. T3 homes
showed a 50% reduction in water use (74 mm per month). Average monthly water use among the
three irrigation treatments differed statistically (p<0.001). Increasing the proportion of landscape
area from 23% ornamental plants irrigated with sprinklers (T1 and T2) to 62% ornamental plants
irrigated with micro-irrigation (T3) saved the most water. Micro-irrigation applied low volumes
of water to only some of the landscaped beds and then only to the root zone.
2.3.27 Evaluation of Evapotranspiration and Soil Moisture-based Irrigation Control on
By M. Shedd, M.D. Dukes, and G.L. Miller.
Presented at the World Environmental and Water Resources Congress 2007:
Restoring Our Natural Habitat, pages 1–21.
This study evaluated the effectiveness of various technologies for reducing residential irrigation
in terms of amount of water applied and quality of turfgrass. Two types of soil moisture sensors
(LawnLogic and the Acclima Digital TDT RS500) were tested at low, medium, and high soil
moisture thresholds. Mini-Clik rain sensors were incorporated in seven timer-based experiments.
Three of the rain sensors were set to bypass irrigation at 3 mm of rainfall; four were set for 6
mm. Two ET controllers were tested, the Toro Intelli-Sense controller and the Rain Bird ET
Manager. Timer-based irrigation without a rain sensor irrigating two days per week (2-WORS)
provided a baseline. SMS systems reduced water use by 0% to 63% compared to 2-WORS. Rain
sensors reduced water use by 7% to 33%. ET-based irrigation reduced water use 36% to 59%
compared to 2-WORS. At low thresholds, the SMS systems saved significant amounts of water,
but reduced turf quality to unacceptable levels. The SMSs set at a medium threshold, timer-based
irrigation, and both ET-based systems produced good turfgrass quality while reducing irrigation
water use compared to 2-WORS. Water savings for the medium-threshold SMS systems ranged
from 11% to 28%.
2.3.28 Evaluation of Soil Moisture-Based and ET-Based Irrigation Control in Turf
By A. Vasanth, G.L. Grabow, D. Bowman, R.L. Huffman, and G.L. Miller.
*Abstract only, found through search of the Irrigation Association website.
A study initiated in the fall of 2006 compared two types of commercially available irrigation
control technologies, one based on ET estimates, and the other on feedback from soil moisture
sensors. The amount of water applied and the turf quality from one ET- and two SMS-based
systems were compared to results of a standard timer-based irrigation schedule. Irrigation
frequency was another component of the study. On average, the add-on soil-moisture-based
system applied the least amount of water, whereas the ET-based treatment applied the most.
Once-a-week irrigation used the least amount of water and daily frequencies the most when
averaged across all technologies. In general, all technologies and frequencies maintained
minimally acceptable turf quality, although some systems resulted in noticeably stressed turf
during the last month of the study. The on-demand, SMS-based system provided the best
combination of water efficiency and turf quality.
2.3.29 Precise Irrigation Scheduling for Turfgrass Using a Subsurface Electromagnetic
Soil Moisture Sensor
By J.M. Blonquist, S.B. Jones, and D.A. Robinson.
Agricultural Water Management, Vol. 84, No. 1–2, pages 153-165.
Research objectives were to (1) examine the effects of scheduling irrigation of turfgrass based on
ET estimates from a weather station compared to data from a novel time-domain transmission
(TDT) SMS, and (2) apply a computer-based numerical model to simulate volumetric soil water
content dynamics at the burial depth of the sensor and to evaluate any drainage occurring below
the turfgrass rooting depth.
This article describes an electromagnetic technology that automates irrigation based on
sensed soil moisture. Researchers installed an Acclima Digital TDT sensor in a plot measuring
about 280 m
on the Utah State University Greenville Research Farm. The sensor connected to a
CS3500 controller, which can log estimated water content as well as control irrigation. The
experiment was conducted July 30–September 16, 2004 (a total of 39 days). Two different
sprinkler heads were used, the first a single-impact Rainbird130IBH with a 3/16-inch nozzle that
was used July 30–August 15. During that period the Acclima TDT system applied approximately
13.0 mm of water (13%) more than the amount recommended based on ET estimates from a
local weather station. From August 16–September 16, the sprinkler head was a lower-
driven Hunter1 PGP with #9 nozzle. During that period, the Acclima system used approximately
20.0 mm, or 16%, less water than the recommended amount and 53% less than an average
irrigation rate of 50 mm week. The cumulative totals for the TDT and both sprinklers were
comparable to irrigating based on the ET estimate.
The authors used the HYDRUS-2D numerical model to simulate the dynamics of
volumetric soil water content at the burial depth of the sensor. The model estimated irrigation
and precipitation inputs and ET outputs from the soil proﬁle to predict drainage occurring below
the grass rooting depth of 10 cm. The TDT system could save an estimated $5.00 to $100.00 per
month based on average water prices in the United States and a 1,000 m
irrigated turfgrass plot,
providing a payback period of 6 to 12 months.
2.3.30 LADWP Weather-Based Irrigation Controller Pilot Study: Executive Summary
By A. Bamezai, Western Policy Research.
Submitted to the Los Angeles Department of Water and Power. 8 pages.
This study evaluated two weather-based irrigation scheduling technologies: (1) Hydropoint Inc.’s
ET controller sold under the trade name WeatherTrak, which replaces a controller; and (2)
Water2save LLC’s weather-based irrigation scheduler, which is added to an existing controller.
WeatherTrak utilizes paging technology to receive weather-related data signals, internally
processes them, and generates an irrigation schedule. Water2save is an interrupt and control
device equipped with wireless Personal Communications Service technology that allows two-
way communication between Water2save and the device.
The goals of the study were to (1) assess the performance of weather-based irrigation
technologies, and (2) assess customer acceptance of those technologies in predominantly non-
single family residential and small commercial settings. The study recruited 25 sites comprising
about 83 acres of landscape (35 acres of turf, the rest shrubs), including homeowner associations,
schools, commercial sites, and public parks. Water use was tracked for at least a year after the
controller retrofits, and statistical models were used to compare two years of pre-retrofit to 1 year
of post-retrofit consumption, accounting for weather. Both technologies rely on broadcast signals
and adjust irrigation patterns to respond to weather conditions. Water2save’s and Hydropoint’s
technologies reduced irrigation by 28.3% and 17.4%, respectively. Because Water2save’s sites
experienced more wasteful irrigation before the retrofits, they had a higher conservation
potential. The percentage of pre-retrofit conservation potential converted into savings was higher
for Hydropoint’s landscapes (95%) than for Water2save’s (71%), however. The authors
estimated that both technologies together reduced outdoor consumption by 27%, achieving about
78% of total pre-retrofit conservation potential. Estimated outdoor water consumption savings
across all test sites in the study was roughly 17 inches per year for pure turf landscapes and an
assumed half of that for pure shrub landscapes. Savings estimates from this study closely
matched the results of at least two previous studies in Irvine, CA.
2.3.31 The Residential Runoff Reduction Study
By The Municipal Water District of Orange County and Irvine Ranch Water
The Residential Runoff Reduction (R3) study tested the effects of weather-based (ET) irrigation
controllers and an education program on irrigation water use and the quantity and quality of dry-
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