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It?EUR??,,????'?????< Even the most efficient, properly designed, installed and maintained irrigation system will waste water if the controller is not programmed correctly. It is estimated that most irrigation controllers are set to overwater the landscape by about 30 percent on an annual basis; this is primarily due to the fact that they are programmed to irrigate too often, and/or the programs are not trimmed back (or turned off) during the cooler months of the year. In order to know how much water to apply, and how often, it helps to know a little about soil type and texture. The goal here is to determine how much water the soil can absorb before water is wasted due to deep percolation and/or run-off. Soil types and textures vary greatly around the country, from sandy to loamy to heavier tighter clay soils. (See map opposite.)
Even the most efficient, properly designed, installed and maintained irrigation system will waste water if the controller is not programmed correctly. It is estimated that most irrigation controllers are set to overwater the landscape by about 30 percent on an annual basis; this is primarily due to the fact that they are programmed to irrigate too often, and/or the programs are not trimmed back (or turned off) during the cooler months of the year.
In order to know how much water to apply, and how often, it helps to know a little about soil type and texture. The goal here is to determine how much water the soil can absorb before water is wasted due to deep percolation and/or run-off. Soil types and textures vary greatly around the country, from sandy to loamy to heavier tighter clay soils. (See map opposite.)
These various soil types differ in their ability to hold water that is available for the plant material to intake. Sandy soils have a much lower amount of available water than do clay soils, and these looser lighter soils need to be irrigated more frequently than clay soils. The heavier, denser clay soils should be watered for longer durations, but less often. If you are unsure of the soil type in question, it is a good idea to take a soil core sample with a soil probe; this will give you a good idea of average root depth as well. A few hours after an irrigation cycle has finished, take a sample at least 12 inches below grade, and see exactly how far down the water is penetrating. To encourage deeper rooting, let the top 50 percent of the root zone dry out completely before watering again.
Another helpful number to know is the approximate precipitation rate of the sprinklers. This is the rate (measured in inches per hour) at which the heads deliver water to the landscape. Keep in mind that the precipitation rate depends on the spacing and the flow rate of the sprinkler heads. Generally speaking, fixed sprays have a precipitation rate between 1 to 3 inches per hour, gear driven rotors between .1 and 1.5 inches per hour, and impacts between .1 to 2 inches per hour. Check the manufacturer?EUR??,,????'?????<
Be sure to take advantage of all the water saving programming features of the controllers under your care. Most controllers have multiple programs available.
Group the zones with similar water requirements into separate programs. For example, turf systems might be in program ?EUR??,,????'?????<
Since all plant?EUR??,,????'?????<
Consider also trimming back on or increasing your base schedule by using the controllers budgeting option (if available). This feature when engaged automatically alters the duration of each station by a determined percentage.
With most AC controllers, these budgeting changes remain in effect until changed by the programmer, however some controllers (DIG Corp?EUR??,,????'?????<
In most climate zones, a rain sensor is a must (they are required in many areas) and for good reason, they work! If one is present on a site, it should be checked out visually and cleaned if necessary. Trip it manually and verify that it is not turned off and has a viable electric connection with the controller. If there is not a rain shut off device on the site, why not suggest the installation to the client as a water saving up-grade? The time-tested Mini-Clik (Hunter Industries) is reliable, adjustable, and is available in an easy to install conduit version.
By implementing these programming practices, and making periodic informed adjustments to your controllers, you will save more than just water and money.
For more information on irrigation scheduling, go to www.irrigation.org
Raleigh, North Carolina
Francisco Uviña, University of New Mexico
Hardscape Oasis in Litchfield Park
Ash Nochian, Ph.D. Landscape Architect
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