Efficient irrigation: Watering and conserving

sprinklersJust by following a few simple guidelines, water-wise gardeners can create hearty landscapes that can withstand hot, dry conditions.

Pros & cons of different irrigation systems.

A good way to prevent overwatering is to install rain or soil moisture sensors to override your automatic watering system when necessary. A rain sensor simply senses rainfall. Once a designated amount of water has been detected, it shuts down any regularly scheduled irrigation. Rain sensors are small, simple devices and are generally less expensive and easier to install and maintain than soil moisture sensors. Soil moisture sensors are more accurate than rain sensors because they can detect moisture at the level of the root system. They are more exact in measuring how much water your plants are receiving and thus offer greater water savings. However, they are somewhat complicated to install and manage.

Sprinkler Systems

  • Sprinklers can cover large areas.
  • Manual sprinklers require you to open the valve, time the watering yourself and then shut off the flow.
  • Automatic sprinkler systems offer the benefit of programmable controllers.
  • Make sure you set automatic sprinklers correctly and adjust it as conditions change.
  • Water early in the morning to reduce the evaporation rate.
  • If water runs off your yard, split your watering times into two or more sessions.
  • Be sure to turn off your system if you’re getting enough water from rain showers.

Drip Irrigation

  • This system is good for a small yard or for watering individual plants.
  • Drip irrigation is highly effective at supplying one to four gallons of water per hour directly to the soil.
  • The advantage of drip irrigation over sprinklers is that there is little water loss due to evaporation or runoff.
  • It’s particularly good for mulched areas because it can directly soak the soil without washing away the mulch.

Hand watering

  • The simplest and most common irrigation system is a garden hose or a portable sprinkler.
  • The advantage of hand watering is that you can easily avoid over watering.
  • Use a nozzle to control the flow.
  • When water stops being absorbed into the ground, move to another location.
  • Wait an hour, and then plunge a long screwdriver or space into the ground to check that the soil is moist to a depth of six to ten inches.

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Watering by the numbers.

Using a hose without a nozzle is an inefficient way to water. It delivers water much more quickly than the landscape can absorb it, causing runoff that wastes water and carries away precious topsoil. It’s better to use a watering can for hand watering. Water each plant once, then repeat 15 minutes later after the water has soaked into the soil. If you must use a hose, make sure to attach a hose nozzle so water comes out in a spray and can easily be turned off when not in use.

There are three steps to practical landscape watering. Follow these three steps to figure out the best watering plan for your two main plant types:

  1. Know how much water your plants need.
  2. Know how much water each part of your watering system applies.
  3. Match your watering system output to your plants’ needs.

Water-wise lawn watering

  1. How Much Water Does Your Lawn Need? For lawns, water deeply but infrequently to encourage deep roots. The key to watering your grass is to apply enough water to soak down to the depth of the roots. The amount varies with soil type, but a good guide is to apply no more than one inch of water every time, which is enough to soak the soil to between six and 10 inches.
  2. Measure Your Sprinkler Output Without knowing it, you could easily drop up to 300 gallons of water in one hour and end up over-watering your lawn. Here’s how to test your sprinkler output so you can adjust your watering time:
    1. Place six to eight shallow, flat-bottomed cans at scattered locations around your lawn. Tuna or cat food cans work well.
    2. Run your sprinklers for 15 minutes.
    3. Use a ruler to measure the depth of water in each can. Add all the numbers, and then divide by the number of cans to find the average output.
    4. This average number is your sprinkler number. It is the average amount of water your sprinklers apply in 15 minutes.
  3. How long and how often should you water? After you’ve calculated your sprinkler number in the previous step, you can calculate how long to run your sprinklers. Simply locate your sprinkler number in the chart below, and then find the corresponding watering time.
    Sprinkler Run Time to Apply 1 Inch
Sprinkler Number  0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Watering Time(in Minutes) 75 50 37 30 25 22 19 16 15

Now put your numbers to work. Set your sprinkler timer and water your lawn for the correct number of minutes. Wait one hour, and then push a spade or long screwdriver into the ground to see if you’ve soaked the soil to the appropriate depth. It will slide easily through wet soil but will be difficult or impossible to push through dry soil.

By the way, if you run your sprinklers for the correct number of minutes but water pools or runs off your lawn, then you need to split your watering time into two or more sessions. Wait an hour between sessions for the water to soak in.

Now, how often should you water? Water only when your turf is stressed from lack of water. How can you tell? Step on it. If you leave distinct footprints or the grass doesn’t spring back, it’s time to water. As long as you apply one inch of water (don’t forget to include any rainfall) each time you water, then no more than once a week is typically enough to keep your lawn green throughout the summer.


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Water-wise landscape watering.

When watering trees and shrubs, don’t water at the trunk or on the leaves. Neither carries water to the tree. Instead, water under the edge of the leaf canopy, which is called the drip line. That’s where the roots are. If you use drip emitters, place several of them along the drip line. If you water by hand, co ntour your landscape so water collects under the drip line of your trees and large shrubs.


1. How much water do your plants need? Just like grass, the most effective way to water your landscape plants is to water deeply but infrequently. Larger plants, like trees, need more water because they have deeper roots and larger root zones and can store more water. This also means they can be watered less frequently. The 1-2-3 Rule is an easy way to remember how deeply to water:

  1. Foot is the correct depth for small plants, such as groundcovers and annuals.
  2. Feet is the correct depth for shrubs.
  3. Feet is good for large shrubs and trees.

2. How much water does your system apply? Here are some typical output numbers for common plant watering systems. Notice the huge difference between the drip emitter, bubbler and watering hose outputs.

Drip Emitter .5 – 4 gallons per hour
Bubbler .5 – 2 gallons per minute
Hose 2 – 5 gallons per minute

3. How long and how often should I water?
Refer to the chart below write down the watering needs of all of your plants. If you use drip emitters, adjust the number and size of emitters on each plant so that your plants get the water they need in two to six hours. For example, the chart shows that a 10-foot tree needs 59 gallons of water. A good setup for this tree would be six 4-gallon per hour emitters, running for 2-1/2 hours (6 x 4 x 2.5 = 60 gallons).
Water only as frequently as your plants need it. Most plants only need water when they start to wilt. However, some plants look wilted during the day, but actually have plenty of water at their roots and will recover in the evening. If your plants are still wilting at night, they need water.
Gallons of Water RequiredPlant Canopy Diameter in Feet

Plant Canopy Diameter in Feet 1' 2' 3' 4' 5' 6' 8' 10' 12' 14' 16' 18' 20'
Tree 1.5 5 11 16 22 26 38 59 85 115 150 190 235
Shrub 1 4 8 12 17 20            
Small Plant/Groundcover 0.5 2 3.5 5 7 9            

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Other great watering ideas.

Rain Barrel

  • Morning is the best time to water, because watering in the evening can invite fungus to grow on your plants at night.
  • Put a rain gauge in your yard. If you get ¾ to 1 inch of rain in a week, you can skip your next lawn watering.
  • If you have an automatic sprinkler system, attach a rain sensor or moisture sensor shutoff device.
  • Use a rain barrel to collect rainfall and runoff from downspouts. Use the rainwater to water container plants and gardens. Make sure your rain barrel has a good, well-fitted screen so it will not harbor mosquito larvae.

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