|Photo Courtesy of Utah State University Extension.
|Utah State University extension personnel conduct an irrigation audit.
Most people now know that
it’s important to conserve water. For those in the lawn care and
landscape business, and their customers, that means irrigating only as much
as necessary. While that sounds simple, actually applying the correct
amount of water takes some work, and it requires knowing how much water is
actually needed and how much an irrigation system is actually applying.
While every area of the country—even specific
locations within the same region—may have different irrigation
requirements, there are some general rules to follow to help gauge how much
is needed and to be sure the system is supplying the correct amount.
One common challenge is to balance the water needs of
various parts of a landscape. “With turf species, we have a really
good idea about water requirements. A lot of that information is available
locally through land grant university systems. There’s just been so
much more research done on turf than on ornamental plants. It gets fairly
complicated when it comes to ornamental plants,” says Kelly Kopp,
associate professor and water conservation/turfgrass extension specialist
at Utah State University, who oversees irrigation audits.
In situations where both turf and ornamentals are
being watered on the same zone, the amount of water sufficient for turf
will typically be more than sufficient for everything else.
“That’s not true for annual flowers, they require a lot, but in
general, turfgrass is going to be the higher water-using plant in the
landscape,” says Kopp. The simplest approach is to water the turf
efficiently and assume that the ornamentals will be covered sufficiently
with that same amount, she explains. Then, monitor the ornamentals for
signs of under or overwatering.
Part of the reason for our greater understand of the
water needs of turfgrass versus ornamental plantings has to do with the
substantial amount of research that’s been conducted in the golf
course maintenance industry, on sports fields, etc., but another reason is
the sheer number of different ornamentals, each with its own unique water
needs. “There are hundreds of varieties of bluegrass, for example,
but the water use between them isn’t going to vary
dramatically,” she explains. “On the other hand, with all the
different tree species and perennials and shrubs and groundcoverings, there
are just so many that you could spend a lifetime working on the water needs
of all these different things and never even scratch the surface.
It’s just sheer numbers.”
|Photo Courtesy of Utah State University Extension.
correct amount of
the needs of the
in a landscape,
as well as the
of the irrigation
Whenever possible, Kopp says it’s “most
definitely” a good idea to get turfgrass and ornamentals onto
different irrigation zones to better give each the amount of water it
needs. “That requires a lot of front-end planning with both the plant
selection and the irrigation system. For the most part, people are working
with a system that they’ve inherited, but there are some
modifications that can be made to improve existing systems. Adaptors that
can be placed on standard spray heads that will turn them into drip
emitters, for example.”
Even though water needs for various turfgrass species
are generally known and available from extension offices, irrigating turf
efficiently is not always a simple matter. “People never ask,
‘How much water does my turf require?’ They always ask,
‘How long should I run my sprinkler?’” says Kopp.
“They often don’t understand that every system is going to be
different. Just the difference between rotor head versus spray head is
huge. So, I can’t just tell them, ‘Run it for 20
“Some of the challenges in determining the
proper irrigation program for a landscape have to with inefficiency in
irrigation systems, as well as the fact that many people don’t know
how much water their irrigation systems are putting out,” says Kopp.
That’s why the intensive irrigation audits she oversees with begin by
determining what the application rate of a particular irrigation system is.
“Without knowing that, you can’t know how
long to run it to put down, say, 1 inch of water,” points out Kopp.
After all, even if you know how much water a landscape needs, unless you
know the rate of the irrigation system itself, it will be impossible to
ever hit that magic number.
After an audit, most extension agents can provide a
schedule that will vary during the growing season and will be based on
historic climate data, she says. “There are some states that now have
statewide weather networks and can give you real-time data, but most states
are still using historic climate data, which is fine,” she says.
“It typically uses a 30-year average, so in a wet year it will be
overestimating [the plant’s irrigation needs] and in a dry year it
will be underestimating, but it’s much more in the ballpark than what
most people are currently doing.”
Kopp adds that it’s important for those setting
up irrigation programs to keep in mind that turf and other plants typically
don’t need as much irrigation during cooler months. “We realize
a lot of savings during the fall and spring,” says Kopp. “Most
systems are set up for the middle of the summer, and then they never adjust
it. We really emphasize changing the schedule throughout the growing
Jacob Johnson, conservation specialist with the city
of Austin (www.waterwiseaustin.org), wholeheartedly agrees about
factoring in the season when programming an irrigation controller.
It’s one of the things that program emphasizes when conducting
irrigation audits. “After we offer a recommended schedule, we ask
that the operator of the system become actively involved with it,”
says Johnson. “Our recommendations are for the summer, but we really
encourage people to seasonally schedule, during the spring and fall; when
it’s cool at night and the ET rates are down, you can get by with
less,” he explains.
Johnson says another common water-wasting mistake is
“watering up” to the needs of one specific plant or area.
“On a zone, if there’s one plant that has a high water need,
they want to run that zone for a long time. Instead, we recommend watering
at a rate for the rest of the plants and then hand-watering that one plant
that needs more,” he explains. “If you see that one larger area
needs more water, that doesn’t mean you want to water the entire yard
more,” says Johnson.
After first determining how much water an irrigation
system is putting out in gallons per minute by monitoring the water meter
during operation of each zone, the auditors in Austin then “walk the
system” to look for deficiencies as well as take stock of the
landscaping. “We look at plant material, the sun exposure, etc. We
also look at the soils. Around here we have a lot of clay soils, so we
factor that into the recommendations,” Johnson explains. Those
recommendations are also based on water requirements for the turfgrass in
question, as well as historic ET rates.
Austin’s irrigation recommendations uses a
two-day-per-week irrigation cycle designed to provide effective, deep
watering. “That gets the water deep into the rootzone, while giving
the ground enough time to dry out so that the roots continue to look for
water. If you water every day, the roots know they’re going to get
water so they can stay shallow, which can lead to more problems,” he
Johnson emphasizes that even after a professional
provides a recommendation for irrigation, it’s important to monitor
the plants. “If it’s doing really well on the recommended
schedule, you might be able to bring the irrigation down a little
In Utah, where Kopp has been involved with irrigation
audits for 10 years, she says that over that time the typical distribution
uniformity of the irrigation systems evaluated is about 50 percent.
“That means that if you’re trying to apply an adequate amount
of water, you’d have to run it for twice as long. With that low of
efficiency, we really shouldn’t even give people a program, but this
is a public program, so we talk a lot with them about how to improve the
efficiency and then give them a program,” she says.
About 10 to 15 percent of the audits conducted by the
Utah State University extension personnel are on commercial or
institutional landscapes with professional grounds managers.
“That’s really fun, because we can talk about a lot of
different issues in depth, they’re excited and motivated, and we know
that they’re going to use the information,” she says.
Kopp has also given workshops to professional
landscapers to help them do audits themselves. Part of the point of the
workshops was to give these professionals the tools needed to do routine
evaluations of irrigation systems, something that’s important
especially in cold climates. “Every year there’s freezing and
thawing, heads are tilted and popping out of the ground and breaking. You
really have to keep up with it, so that the system is continually operating
as efficiently as possible. If we could get them to turn the irrigation
system on and check it out once a year, I would be thrilled. A lot of times
irrigation systems are run at night and people never even see
Kopp says part of the challenge is making people aware
that overwatering turfgrass can harm plant health. “I sometimes wish
that turf would start showing the detrimental effects earlier rather than
later, but it can take quite a lot of overwatering before it starts having
disease and nutrient issues show up,” she says. “Some
ornamental plants show the effects of overwatering pretty quickly. From a
visual standpoint, turf doesn’t help us very much, so that’s
where education comes in.”
Patrick White is a freelance writer and editor who is
always on the lookout for interesting and unusual stories.