Irrigation Water
Conservation Tips
Irrigation
Scheduling.
As
a general rule watering deeper less often is more efficient. In most cases the
root system on plants, even turf grass, extends 6”-12” below ground level. By
irrigating for short durations (5-15min) you wet only the top inch or two of
soil. This is also the strata of soil that loses the most water to evaporation.
By watering to a depth of 6” or more you can allow the top inch to dry out
while letting the plant draw water from the “reservoir” underneath. You won’t
need to water again until the soil 3”- 4” deep starts to dry. Generally this
cycle is 3-7 days depending on weather conditions. This cycle is also healthier
for turf grass as constantly damp conditions favor fungus development.
Reducing
Precipitation Rates
Precipitation rate
refers to the total amount of water being put out on a given area. This is
usually given in inches per hour (just like rain). By reducing your
precipitation rates you can help reduce run off. To continue with the rain
analogy, by reducing the precipitation rate you have a gentle rain that soaks
in rather than a hard rain that produces runoff.
Suggested Products: Hunter rotor and
MP Rotator nozzles
Subterranean Drip
line
A subterranean drip
line system is a grid of poly hose with in line drippers at 12”-24” spacing
that is designed to be buried 4”-6” below your turf or ground cover. This type
of system is unaffected by wind and low humidity. It can have up to a 97%
system uniformity. This combination of high uniformity and no losses to wind,
air evaporation, run off, or overspray make this an extremely efficient system
that will save water. Suggested Products: Netafim Techline; Rainbird Landscape
Drip line.
Products: Netafim
Techline, Rainbird Landscape Dripline (Hunter has a product in development)
Drip / Micro Irrigation
In
shrub areas, planting beds, hedges, potted plants, etc. the most efficient way
to irrigate is with micro irrigation. Micro irrigation allows you to deliver
water directly to soil above the plant’s root zone, eliminating irrigation in
non-target areas. Micro irrigation also allows you to pair up emission devices
to specific plants to satisfy each plant’s individual needs instead of
“averaging” the needs of all the plants in a planter or area.
Suggested
Products:
Hunter Drip Zone Kits; Rainbird 1800 retrofit, and XERI line; Spot Systems;
Olson; Netafim; Point Source; Toro Ag; Roberts and more.
Cycle and Soak
This
is the process of splitting an irrigation run time into several shorter
sections with an interval in between. This practice will help increase water
penetration and decrease runoff. It is especially helpful on slopes or in areas
with extremely compact or clay soils.
Suggested Products: Hunter ICC and ACC
timers.
Mulching
Using
a moderately thick layer of mulch or bark can help reduce water loss to
evaporation from the soil. It can also help with weed prevention.
Suggested Products: Bark (small,
medium, and walk on); Kellogg’s Xerimulch; Grangetto’s or Gardner & Bloome compost; Pine Shavings.
Soil Penetrants
In
areas where there is heavily compacted or clay. Even irrigation with low
precipitation rates, can cause run off regardless of how short the run time is.
In situations like this the use of a soil penetrant is called for. A soil
penetrant is essentially a surfactant, which reduces the surface tension of
water. This allows water to percolate through the tight pore spaces of clay or
compact soil instead of “sheeting” on top and running off.
Suggested
Products:
Naiad; Water Wet from JH Boitech; EZ
Wet from Growmore.
Metering Valves
These
valves are set manually to allow a specific volume of water to pass through the
valve before automatically shutting off. These valves are used mostly in
agricultural applications. They allow you to control exactly how much water you
are using.
Products: Bermad 900 series
and 1106 valves Netafim also has a metering valve
Drain Check
Drain
checks prevent low head drainage after the system is shut down. This also allows
the lines to stay charged minimizing system inrush and saving water.
Suggested Products: Hunter HCV;
Hunter, Rainbird, and Toro pop ups all have a check valve option.
Pressure Regulation
We
have all seen irrigation systems where there is an abundance of mist drifting
away in the breeze. This is caused by having more pressure than the sprinkler
was designed for. As pressure increases the droplet size from your sprinklers
decreases, in other words the higher the pressure you have the more misting you
will have. These problems are even more pronounced in drip and micro irrigation
applications.
By
regulating the pressure to the manufacturer’s recommendation you can save water
in two ways.
First
by reducing misting which, will reduce evaporation losses directly to the air
and as larger droplets are less affected by wind you will get more water where
it is supposed to go.
The
second way is a little more complicated. Every nozzle has an optimum pressure
and at that optimum pressure it has a specific flow rate. As the pressure
increases the flow rate increases. Let’s assume you have a zone with a number
of sprinklers whose optimum pressure is 35psi and your system operates at
80psi. This means that when you irrigate you are putting out as much as 50% more
water than what you intended, most of which is wasted as mist, overspray, or
runoff.
Nozzle
flow rates can be optimized and misting eliminated by regulating the pressure
on the main line, at the manifold, or at each valve. In some cases due to the
length of the laterals or the number of heads on the line you can’t regulate
pressure at the valve without having unacceptable friction losses on the
lateral. The solution in this case is to use pressure compensating emission
devices, pop ups, nozzles, drippers, or micro sprinklers.
Suggested Products: Wilkins
regulators; Senningers; Hunter Accuset; Hunter Institutional and MP pop ups;
Rainbird 1800 PRS pop ups; Toro PC nozzles; Netafim PC drippers; Netafim
Supernet Micro sprinkler; Dan 2001/2002 micro sprinklers.
Sensors
Rain, wind,
freeze/frost, and flow sensors can all have a place in water conservation. Rain
sensors eliminate irrigation cycles when there has been sufficient rain to no
longer warrant irrigating. Wind and freeze sensors eliminate irrigation cycles
that would not be efficient due to weather (either too windy or too cold). Flow
sensors shut the irrigation system down if it suddenly starts flowing a lot
more water than it should (this could occur if there is a broken line or
sprinkler head).
Suggested Products: Hunter Rain Click, Wind Click, Freeze
Click and Flow Click; Rainbird and Irritrol both have lines of sensors for
landscape applications; Netafim has sensors for agricultural applications.
Soil Moisture
Measurement
There
are a significant number of soil moisture devices on the market, however they
can be broken down into a few categories, manual, electronic, and electronic
automatic (for use with a controller). Both the manual and electronic devices
have to be read regularly to determine if irrigation is needed. The only
devices that have an automatic function are those connected to an irrigation
controller.
Suggested
Products:
Jet Fill, Acclima (from Aquarius) Irriwise (from Netafim) Peco Sales has a
number of soil moisture meters that can be special ordered.
Evapotranspiration
Technology
Evapotranspiration
is the amount of water that evaporates from the soil and is used by a plant
(turf grass being the standard). This is generally calculated from temperature,
humidity, wind speed, and other factors. The CIMIS web site, www.cimis.water.ca.gov, has ET
information from stations all over
For
example the
Let’s
assume that we have 70% efficiency with sprayers that have a precipitation rate
of 1.9 inches per hour, this means that you would have to apply 4.01 inches in
January and 10.11 inches in July (These are the actual ET requirements divided
by the system efficiency percentage 2.81/.70=4.01).
In
a typical landscape, sprayers are run for 10 minutes a day, every day. This
means that you are applying 9.42 inches per month, more than double what is
needed in January and not quite enough in July. (10 minutes is .16 hours x 1.9
inches per hour = .304 inches per application x 31 days = 9.42 inches per
month)
By monitoring the ET data available and
adjusting your irrigation run times accordingly you can save a significant
amount of water. There are data bases online that explain the procedures for
adjusting the ET data for plants other than turf grass, this will be especially
helpful in agricultural irrigation.
Smart Controllers
There
are a number of ET based “Smart” controllers on the market. These controllers
use ET data, either from their own on site, mini weather station or a monthly
subscription from a service, to automatically calculate the irrigation run
times for optimum water conservation.
Suggested Products: Hunter ET system
(compatible with ACC, ICC and ProC timers); Irritrol Smart Dial; Toro
Intellisence; Netafim Irriwise (Toro recent buyout of Rainmaster should soon
give us a access to their line of ET based timers).
Conclusion
The
best results will be found by those who implement most or even all of the tips
above. Each tip (or retrofit) will result in some water savings, how much
depends on the efficiency of the original system.
ET based timers do not guarantee that you will
use less water but, if programmed properly, they will use the correct amount of water. Just as in our
example, in the month of July, the ET based timer would have watered more than the original system, however
in most of the rest of the months the ET timer would have watered considerably
less, thereby saving a significant amount of water.
So if you can incorporate some of these tips
to increase system efficiency and use ET to determine how much water is needed
at what time of year you can save significant amounts of water.
To
offset the initial cost there is rebate and grant money available for irrigation
upgrades as well as the savings on the water bill.
