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Irrigation Trends Shaping Our Landscapes

Momentum builds to reduce potable water use on turf and what it means to you
By Michael E. Dukes




Irrigation product suppliers and property owners must partner to drive irrigation efficiency to keep the green industry healthy.
PHOTO COURTESY OF TORO.

Designed and managed landscapes, which typically include in-ground irrigation, are common in many urban and urbanizing areas of the United States. While these landscapes can have aesthetic and other functional benefits, they have also been under scrutiny due to the inputs to maintain these landscapes at a desired level of quality or performance. In particular, water and fertilizer inputs have come under scrutiny due to the demand imposed on municipal water systems (where potable water is the source of irrigation) for the former and downstream water quality degradation for the latter. This article will focus on the issue of water as an input and some trends that are shaping landscapes of the future.

In the past, a number of strategies have been utilized in an attempt to reduce potable irrigation demand on landscapes. Relative to irrigation, the following are somewhat common tools: day of the week irrigation restrictions, requirement of a rain sensor, use of water budgets, requirement of a certified and trained professional to design and install the irrigation system. Some other less common requirements include a required threshold level of distribution uniformity (DU) and some measure of proper design and installation in the field such as field verification of irrigation install compliance with a design.

These strategies have all been used where potable water is used for irrigation. Increasingly, alternative water supplies such as reclaimed wastewater, lower quality surface water or shallow wells are being encouraged. Even these alternate sources, which were once thought to be plentiful if not almost limitless are showing signs that limits might exist with some utilities now volumetrically metering reclaimed wastewater for billing purposes. Landscape techniques aimed at reducing potable water demand include: restricted plant lists, turfgrass area restrictions, and restrictions on the amount of irrigated area in the landscape.

Reducing potable water use

In recent years, tremendous interest has occurred with programs aimed at reducing the amount of water applied to landscapes and in particular when potable water is used. A well known program is the EPA WaterSense program (http://www.epa.gov/watersense/index.html) includes a water budget tool for landscapes (http://www.epa.gov/watersense/water_budget/).

The water budget tool is intended to influence the design of the landscape considering plant and turfgrass water usage that would be capable to thrive on a reduced allocation of water compared to "typical" practices whether an irrigation system was installed or not. Other programs such as Florida WaterStar (http://www.sjrwmd.com/floridawaterstar/) and LEED (http://www.usgbc.org/leed/homes) for homes are more prescriptive, offering points for landscaping and irrigation practices intended to create more water efficient landscapes.

Rather than a quantitative water budget that can be used in the design process, the designer most pick from a menu of options which are then assigned point values corresponding to the relative potential for water conservation. For example, not irrigating a significant fraction of the landsape would allow for more points than say using pressure regulation in the sprinkler system. A certain number of points in various categories such as percentage of the landscape not irrigated, percentage of the landscape without high volume irrigation, use of a smart controller, leak detection and rainfall harvesting as the irrigation water source (WaterStar) and limiting turfgrass, use of drought tolerant plants, and reduce irrigation demand by at least 20 percent, (LEED for homes) are required for certification.

The programs described here are voluntary. On the other hand, codes, once adopted by local governing bodies are mandatory. Examples include local building codes and electrical codes. Organizations developing codes cite "standards" in their language. A "standard" is essentially a consensus of stakeholders on an agreed upon way of doing something. The "something" could be how a product will be manufactured or how it will perform or how a design will be conducted so as to meet certain specific and measurable criteria.

Standards are used in codes such as the Florida Building Code. A building code is a specification intended to protect health, provide safety in the built environment, and addresses the manner in which systems are assembled or constructed in the field. Standards strengthen codes since they function as references for very specific aspects of a code.

Characteristics of Landscapes of the Future

Use substantially less or possibly no potable water for irrigation.

When potable water is used we can expect drastically less sprinkler irrigated area. With many common turfgrass varities, this will necessitate less turfgrass area or new varieties that can exist on only rainfall.

Larger amounts of landscaped area will contain microirrigation or a significant amount of the landscape will not be irrigated. Expect to see trials of subsurface drip or buried capillary mats in turfgrass.

Dual supply systems will become more common as alternative water supplies (e.g. reclaimed wastewater and other lower quality wter sources) are increasingly used to offset potable water use for irrigation.

Smart irrigation controllers will become mainstream so that the efficiency of irrigation scheduling will be maximized.

Onsite rainfall capture will increase in popularity. Greywater may be coupled with such a system as yet another way to offset potable water or other sources for irrigation.

Standards under development

There are currently several ongoing standards development efforts related to landscape irrigation. The "Standard for Landscape Irrigation Emission Devices" (http://www.iccsafe.org/cs/standards/IS-IEDC/Pages/default.aspx) initiated by the International Code Council (ICC) has undergone the first round of public comment. This standard aims to establish minimum requirements for landscape emission devices to ensure adequate safety and performance through common testing and specification procedures. Currently testing and specification guidelines vary across the industry for sprinklers and microirrigation.

This new standard will allow an "apples to apples" comparison of device specifications which should allow more efficient irrigation.The American Society of Agricultural and Biological Engineers (ASABE) is currently overseeing four standards development efforts (http://www.asabe.org/standards/landscape-irrigation-standards.aspx)as follows: 1) Landscape Plant Water Requirements, 2) Weather-based Landscape Irrigation Controllers, 3) Auditing of Landscape Irrigation Systems and 4) Soil Moisture Sensor Landscape Irrigation Controllers.

The Landscape Plant Water Requirements standard will establish a common methodology for determining water requirements of landscape plants while maintaining intended function of those plants based on the most current scientific knowledge. Such a standard could be used to define a landscape irrigation budget for either management or how a landscape might be designed.

Currently, there are many different ways used to determine landscape water requirements that vary across the county and in some places city by city. This creates a patchwork of requirements that aren't always based on the latest science.

The Weather-based Controller standard aims to provide a common testing methodology to characterize an efficiency of these controllers. This standard will build on the existing efforts of the Irrigation Association Smart Water Application Technologies test protocol development (http://www.irrigation.org/SWAT/) and the WaterSense controller specifications (http://www.epa.gov/watersense/products/controltech.html).

The Auditing standard is in process of defining minimum requirements for performing a catch can test and is using the Irrigation Association Recommended Audit Guidelines as a starting point. This standard committee is also looking at developing minimum requirements for auditing drip systems as well as performing an audit using a soil moisture sensor because there are also many variations across the country on how to audit a landscape irrigation system.

Variation necessarily leads to differences due to the evaluation process itself making it difficult if not impossible to specify minimum performance levels across a broad area.

Finally, the Soil Moisture Sensor Controller standard will describe a methodology to test the performance characteristics of soil moisture sensors in various types of soil, salinity levels and temperatures. Common testing, specification and evaluation of landscape irrigation technologies, equipment and systems will lead to an even playing field for the industry while achieving higher levels of water use efficiency.

Michael A. Dukes, Ph.D., P.E., C.I.D., is with the University of Florida, Institute of Food and Agricultural Science, Center for Landscape Conservation and Ecology, Agricultural and Biological Engineering Dept. Contact him at mddukes@ufl.edu.