Irrigation Systems Irrigation Scheduling
Watering your landscape with an automatic irrigation system will likely be the single largest use of water in your home. You can dramatically improve efficiency by using proper irrigation scheduling techniques such as those outlined below.
In the best of all possible worlds your irrigation system would supply your landscape with exactly the right amount of water to keep it healthy. The system would shutoff when it rains and would increase watering times during dry spells. The perfect system would supply different amounts of water to different types of plants and would eliminate over-spray onto sidewalks and pavements. The perfect system would only run at night to minimize evaporation losses and it would alert you if there was a broken head or a stuck valve or some other problem.
Unfortunately, the perfect irrigation system does not exist. Some new technologies to control irrigation based on weather patterns are being tested across the country (see Irrigation Future Trends), but until these products reach the mass market, irrigation scheduling and clock programming is a regular chore for many homeowners.
Proper irrigation scheduling is a skill that surprisingly few have mastered. Many people don’t realize that they must change their irrigation program regularly as the seasons change. Ideally you should program your sprinkler clock weekly or even daily to maximize efficiency. But even monthly changes to the irrigation schedule will result in substantial water savings and improved plant health. You should turn the system off when it rains and make frequent adjustments to the timing of each zone so that just the right amount of water is applied. Few people have the time or inclination to take this micro-managing approach, so these tips are designed to help you maximize efficiency with your sprinkler system through sensible scheduling.
The biggest problems encountered are watering too much and too frequently. Many of the common turf grass and landscape shrub diseases are made worse by, or even may be the result of, watering too frequently.
Irrigation Scheduling Tips
Water At Night
Understand the Water Needs of Your Plants
It is important to understand the needs of drought-tolerant plants. These plants are often native to arid climates where it rains heavily for short periods, followed by long periods with no rain at all. The drought tolerant features of arid region plants allow them to survive and even thrive under these feast or famine water conditions.
Drought tolerant plants may be found growing in all types of soils, from sand to clay. Sandy soils do not hold moisture well, and drain quickly. They are the easiest soils to grow drought tolerant plants in when irrigation is available. Clay soils hold water tightly for long periods of time, and cause the most problems with over-watering. Watering needs to be much less frequent in clay soils to allow the drying time that these plants need.
Never Water if the Soil is Wet
The first basic irrigation scheduling rule for drought-tolerant plants is never water if the soil is still wet. The old rule for landscape care was "if it doesn't look right, water it". This is often the worst possible thing to do. Plants wilt for any number of reasons other than needing water. Wilting for some perennials happens on hot afternoons no matter how much water they have.
Wilting in drought tolerant plants is often the first sign of too much water. The roots die from too much water, then the plant wilts from lack of water uptake by the roots. Any number of other diseases or even insect damage can also cause wilting. Some drought tolerant plants fold their leaves on hot afternoons to conserve water, which can be mistaken for wilting. So never assume a plant needs to be watered because it looks wilted. Check to see if the soil is wet first.
When You do Water, Don't be Stingy
Cycle Your Sprinklers
Technical note: in large areas of turf you may not notice the run-off because the water doesn't run into a gutter or over a sidewalk, but runs off to the lowest area in the lawn. It's still critically important to prevent the run-off. If you don't, muddy, wet areas will result where turf diseases will thrive, mosquitoes will breed, and your mower will leave ruts.
Avoid Cycling Drip Systems
The problem with a drip system is saturating the soil throughout the entire planter area, not just the soil directly under the emitter. To saturate the entire planter area the water has to move outward in the soil from the emitter locations. In all but the sandiest of soils the water can be forced to move at least 36 inches in each direction away from the emitter through a combination of positive displacement and capillary action.
To achieve the positive displacement part of this action it is necessary to avoid cycling the drip system. Run the drip system as long as possible at a time. Create small berms if necessary to control run-off. In some clay soils you may need to cycle the drip system like you would a sprinkler system to avoid run-off, but try to keep it down to just one repeat cycle if possible. Remember, if you can't achieve saturation of the entire planter area, you at least want the wetted area around each emitter to be as big as you can make it in a single 24 hour period. You may even need to add more emitters to achieve the goal. If you do add more emitters, space them at least 36 inches apart. Remember, the goal isn't to add more water to the areas that are already wet, the goal is to wet more area for the roots to grow in.
Click here for information on different drip emitters and their precipitation rates.
Multiple Start Times
Table 1: Sample watering schedule
Start times: 12:30 a.m., 2:00 a.m., 3:30 a.m.
Adjust Your Schedule As Needed
Some sprinkler clocks have a rain pause button that enables you to postpone irrigation for a day or more. On other clocks it is easy to shut the entire system off for any period of time. Some newer clocks also have % increase/decrease feature. This is a nice feature that enables you to reduce or increase watering across your entire system by a fixed percentage. This feature makes it much easier to adjust your clock for changes in the weather.
Consider a Rain Shutoff Device
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