District News Articles

  2. Reprinted with the permission of Kristin Shewfelt, McStain Neighborhoods


    From 1996 to 1999, The American Water Works Association (AWWA) Research Foundation conducted a study to determine how North American households use water around the home.  A total of 14 cities, including Boulder and Denver, participated in the study.  AWWA concluded that North American households typically use about 146,000 gallons of water annually, and of this amount, approximately 42% is used indoors and 58% is used for outdoor irrigation.  Given that meaningful savings in indoor water use is often difficult to obtain, as use is shaped by homeowner behavior and primarily influenced by price signals, the potential for water savings by reducing irrigation demand in the residential sector is significant.  Indeed, water run-off attributable to inefficient irrigation has long been known.  In addition to its negative economic impacts, excessive water moving over the ground often absorbs many pollutants, including fertilizers, herbicides and insecticides, which are eventually deposited in receiving waters, groundwater supplies and wastewater facilities.  The EPA reports that these pollutants have harmful effects on drinking water supplies, recreation, fisheries and wildlife.


    Fortunately, many strategies exist right now to maximize irrigation efficiency.  On-surface drip irrigation systems for trees, bedding areas and shrubs, for example, deliver precise amounts of water slowly and evenly at the plant’s roots, eliminating water waste, run-off and overspray.  Slow soaking also encourages plants to develop deep root systems that are better able to tolerate drought.  Sub-surface drip systems, developed in the dry climates of the Middle East, have made small inroads in the Denver market, although there is not yet consensus on their efficiency or long-term maintenance challenges.  Subsurface systems use a flexible drip irrigation pipe which is buried a few inches below the irrigated area with a soil moisture sensor control.  Proper installation, however, is critical to the success of these systems, as improperly designed systems may present water distribution problems that may be difficult to correct.  Other irrigation products that can be used to manage water more efficiently include rainfall sensors, pressure regulation devices, check valves and high-efficiency nozzles, among others.


    Newer technologies are continually being developed and tested and are changing the way the residential sector can water its landscapes.  In 1998, the Metropolitan Water District of Southern California (MWD), The Municipal Water District of Orange County (MWDOC) and the Irvine Ranch Water District (IRWD) designed a study of a new ET Controller technology to address home water use efficiency.  ET refers to evapotranspiration, or the combination of water that is evaporated from the soil or plant surface or transpired by plants as part of their metabolic processes.  “Reference evapotranspiration” or “ETo” is simply the amount of water (in inches), needed by bluegrass in our area to replace water evaporated or transpired.  Bluegrass, rated at 100% ETo, and a high water use turf, is used as a reference for other plants.  Low-water use plantings, for example, use anywhere from 25% to 49% of ETo.  Understanding ET data is one of the most important things to consider when scheduling run times for irrigation systems.  In theory, the ET Home Controller technology was designed to receive locally broadcasted ET data via a satellite system, encode it and automatically readjust the irrigation system flow times to match the actual plant water needs. 


    In order to test this concept, the WeatherTRAK ET controller (see was installed in 40 test homes, with 40 control homes that received no treatment, and 40 “postcard” homes receiving monthly watering time instructions via mail.  Preliminary results indicated an average reduction in landscape water use in the test homes of 20%.  A 2001 follow-up study indicated a savings of 18%.  40 out of 40 residents claimed they never had to touch the ET controller to set or re-program as weather changed.  As a result of this research, ET Home Controllers now on the market will be included in Denver Water’s Summer Outdoor Rebate Program as an irrigation system upgrade that can be linked to one of Denver Water’s many weather stations.