Irrigation Scheduling
Irrigation Scheduling
 Irrigation Systems
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Lawn 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

The Basics

  • Know how to run your controller and change watering times.
  • Adjust the watering times (number of minutes.) and the frequency of watering (daily, twice a week, etc.) based on weather conditions.
  • Change your settings to adjust for seasonal differences and reset the timer when needed.

Water At Night
Make sure your system only operates when the sun is down to reduce evaporation losses. If you like to watch your sprinklers run, set the start time for 8:00 p.m. – there is still plenty of light outside, but the sun is usually down. Many experts say the best time to water is between midnight at 4 a.m. because evaporation in kept to a minimum.

Never Water if the Soil is Wet
Irrigation scheduling is simply a matter of close observation and dedication. Ideally, the irrigation control clock should be adjusted on at least a weekly basis to conform with current weather conditions, but even with monthly adjustments your lawn can be maintained healthy and happy.

The first basic irrigation scheduling rule 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.

When You do Water, Don't be Stingy
The other rule for irrigation scheduling is when you do water, don't be stingy. Saturate the soil. The soil should be completely saturated (the technical term is that the soil has reached field capacity) throughout the root zone.

Cycle Your Sprinklers
If you're irrigating using sprinklers, the water will probably start to run off into the gutter, or into a low spot, before the soil is wet through the root zone. This is because the sprinklers put out more water in a given amount of time than the soil can absorb. In technical terms the precipitation rate of the sprinklers is greater than the infiltration rate of the soil. (Both, by the way, are measured as inches/hour in the U.S.A.) Fortunately, solving this problem is easy. As soon as the water starts to run-off, just turn off the sprinklers! Wait an hour or so for the water to soak in, then run the sprinklers again until run-off once again occurs. Continue this run-stop-wait-run cycle until the soil is saturated through the root zone. This process is referred to as cycling the sprinklers. Almost all sprinkler systems need to be cycled for proper irrigation.

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.

Multiple Start Times
If your irrigation controller offers the feature of multiple start times you can use this to your advantage. Most modern controllers offer the option of 2 or three start times. When this feature is implemented your system will run through the entire cycle of zones more than once per day also called cycle irrigation. Here’s an example: Instead of watering zone 1 for 20 minutes, use the multiple start time feature and set up three start times. You can then water zone 1 for 6 minutes three times for a total of 18 minutes. The shorter run times will reduce runoff and water losses and will reduce deep infiltration below the root zone. Table 1 shows a sample watering schedule using multiple start times.

Table 1: Sample watering schedule

Zone & Plant Type
Sprinkler Type
# of Starts
Minutes Per Start
Total Minutes
1 Lawn
2 Lawn
3 Groundcover
4 Shrubs
5 Garden
6 Trees

Start times: 12:30 a.m., 2:00 a.m., 3:30 a.m.

Adjust Your Schedule As Needed
The weather changes. The seasons change. Your irrigation schedule should change to reflect the prevailing climate and season. Generally at the beginning of the irrigation season (typically the spring) you don’t need to water as frequently as you do in the middle of the summer. In the early fall you can once again cut back watering.

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
Irrigating during or right after a rainstorm is one of the most pointless and wasteful irrigation practices. But what are you going to do if you’re on vacation or out for the evening when the rain comes? A rain shutoff device may be the perfect solution.

Source: (accessed 7/11/01). Permission granted.

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