New Paradigm in Water Conservation - Use a Professional

Written by Administrator
on 18 January 2023

 

 

 

 

 

Residential Irrigation Water Savings from Professional

Installation of Smart Controllers in the Twin Cities

 

December 2022

 

 

Leonard R. Ellis, PG, CLIA

Safe Water Commission, LLC

Maplewood, Minnesota

 


Introduction

The purpose of this paper is to accurately estimate water savings for residential irrigation systems in a suburb of the Minneapolis/St Paul, Minnesota (the Twin Cities) by replacement of standard irrigation controllers with Water-Sense Certified smart controllers as part of a new Smart Irrigation Program (SIP).

History and Previous Studies

Water conservation is a serious issue in much of the country, particularly California, and consequently, it has historically taken the lead in water conservation issues. A 10-year old report called Smart Irrigation Technology Stories – Three Communities, Three Experiences discusses the effect of conversion of old irrigation clocks to smart controllers.  The limited data presented said that pilot studies performed early in their efforts achieved 20% to 25% water savings by switching to smart controllers.  No detail is provided in the literature on the pilot studies.

The climate in Minnesota is significantly different from California and much of the country where water conservation studies have been in the forefront such as southwest and southeastern United States.  In the northern continental climate in the Twin Cities, yards need much less water in the early and late part of the typical 24-week season than the middle part of the summer.  Quality smart controllers have adjustable settings which will skip run days when maximum high temperatures are below a set threshold (if properly set up).  Since old control clocks are set up to run the same days and times each week for the entire season, the results are significant overwatering and water wastage early (from mid-April and May), and again late in the irrigation season (from mid-September to mid-October).

A more recent and applicable study on water savings of Smart versus conventional irrigation clocks was performed in 2017 and 2018 by the University of Minnesota Agricultural Extension. Although the work started in July in both years, the different smart controllers evaluated showed between 21- and 76-percent water savings with an average of approximately 47 percent (University of MN Agricultural Extension, 2019).

Woodbury, Minnesota has been a leader in the Twin Cities in water conservation which started because the city wanted to ameliorate the four-fold increase in water pump rates in summer versus winters (16-million gallons versus 4-million gallons).  The City completed a two-year pilot program with help from the Minnesota Technical Assistance Program (MnTAP), South Washington Watershed District and Washington County in 2019. This program was considered to be successful, saving each home that was part of the program an average of 30,000 gallons of water each year. The city then chose to implement a do-it-yourself program in which residents purchase city-bought controllers at a significant discount, self-install, and set the runtimes according to their own preferences.    

 

Pilot Study History and Purpose

In the summer of 2020, the Stillwater Board of Water Commissioners, in conjunction with the Brown’s Creek Watershed District, sponsored a pilot program performed by Safe Water Commission. The initial purpose of the pilot study was simply to determine the effectiveness of professional replacement of old irrigation controllers with weather-based smart controllers.  The study consisted of 100 Stillwater city residents who paid a nominal fee to obtain the professionally-installed smart controllers.  Since Safe Water was already going to be onsite and the proof of concept was going to require quantification of the effectiveness of the new controller, Safe Water chose to add an irrigation system evaluation (Simple Audit) to acquire data to determine water saved.  The baseline flow in each zone was calculated for each residence based on the number and type of head, water pressure, and throw and the flow was then calculated for each yard’s irrigation run cycle. 

Of the controllers evaluated, the Hunter Hydrawise Water-Sense Certified smart controller was chosen because of its historical reliability (#1 controllers used in the United States), multiple options, ease of programming, ability to quantify actual runtimes adjusted because of the weather, and its modest price point.

 

SIP Field Process

 The  SIP process is summarized as follows:

·         Record prior settings of the old controllers used to calculate the  baseline volume of water used for each day’s run;

 

·         Collect data from each zone including number and type of heads, water pressure, throw of water stream, and problems with the irrigation heads, valves, or lines as a part of a Simple Yard Audit;

 

·         Remove the old controller, then install and program the Hunter Hydrawise, Water Sense Certified controller;

 

·         Add a new, functional rain sensor if the owner chose to have one;

 

·         Educate owners on how to operate the Hydrawise handheld application;

 

·         Prepare a Professional Evaluation Report (often called a Simple Irrigation Audit) for each residence complete with tabulated details of the system evaluation, expected water savings per season, and recommendations for amendments to their system.

 

 

Programming the Weather-Based Controller

Initially, the Hydrawise weather-based controllers were programmed using the original runtimes and then were set to shut off or reduce/increase the next day’s run cycles as follows:

·         Shut off the day’s run if there was greater than 60-percent chance of rain (based on the Weather Underground’s “hyperlocal” data), 0.5-inches of rain in the last 24-hours, or 1.5 inches detected in the last 3-days;

 

·         Shut off the day’s run if the forecast high was lower than 55 degrees Fahrenheit;

 

·         Shut off the day’s run if the wind was expected to be more than 22 miles per hour;

 

·         Reduce the day’s runtimes 30-percent when the maximum forecast high was between 55 and 70 degrees Fahrenheit and increase the runtimes 30-percent if the maximum forecast high was above 90 degrees.

It was realized about a quarter of the way through the study that over half the residences used considerably more water than was necessary for robust lawn health.  Many systems ran every day of the week during the irrigation season and many zones were set to 40 minutes or more, oversaturating the lawn.  Therefore, Safe Water started to professionally set conservative runtimes considering type of head, shade, slope, vegetation and soil type. Runtimes and days run were changed from their original settings for 34 of the 100 irrigation systems. 

2020 SIP Pilot Data Results

The runtime baselines for a day’s cycle for the Stillwater homes ranged from 417 gallons to 3,218 gallons.  The number of days the systems were initially set to run per week ranged from 2 to 7 days. The total baseline water used with the old controllers for all 100 homes, annualized, was 9,753,000 gallons.  With the change in runtimes for 34 of the 100 controllers,’ there was a 29-percent annual savings of 2,829,000 gallons, reducing it to 6,924,000 gallons per season disregarding the effect of the smart controller.

There was an additional 41-percent water savings (2,831,050 gallons) from the smart controller which diminished the volume used annually to 4,093,000 gallons.  Therefore, the result of the Pilot Study showed that there was an average of 42% of the original baseline used (4,093,000 gallons/9,753,000 gallons) on the yards or a 58-percent annual savings in water usage.

No client complaints were made to Safe Water that anyone’s yard suffered as a result of less irrigation from this program. 

Conclusions

The professional audit with its conservative runtime settings for 34-percent of the residences, saved the entire program 29-percent in average water used per season.  After this reduction, the additional savings from the smart controller of 41-percent, yielded a total annual savings of water used from the new SIP of approximately 58-percent.  Assuming the pre-existing residential “non-smart” irrigation systems in the Twin Cities are similar to Stillwater (which subsequent SIP data suggests is true) and that they average 1,150 gallons per run, 3,500 gallons per week, and about 82,800 gallons per season, then suburban cities in the Twin Cities can expect to save an average of approximately 48,000 gallons per program participants per season by performing the SIP and with little if any negative impact to yard health or appearance.

If 1,000 residential irrigation systems in a growing Twin Cities suburb such as Eagan, Eden Prairie, Plymouth, Edina, Maple Grove, Lakeville, Blaine, Apple Valley, Woodbury etc. benefited from the SIP, with the life of the controller at just 10-years, then a conservative estimate of 500,000,000 gallons of water can be expected to be saved by each of those cities over that timeframe if they choose to follow a program like this.  Given the predicted double digit growth rate of the growing suburbs, this water savings should allow the current water infrastructure to keep up with city growth and future water usage in the next few decades and save millions of dollars.

  

References

Santa Clarita: Two Routes to Water Savings, www.ca-ilg.org , 2012, 3 pgs.

Reducing Water Use on Twin Cities Lawns Through Research Education and Outreach, University of MN Agricultural Extension, 2019, 12 pgs.

Safe Water Commission, Unpublished Data, Stillwater Smart Irrigation Controller Pilot Program, April to September 2020.

Water Efficiency Project – Maximizing Benefits from Community Water Efficiency Programs, Metropolitan Council, April 2019.

Woodbury website:  Residential Smart Irrigation Controller Program | Woodbury, MN (woodburymn.gov)