Sustainable Landscaping
healthy lawn care
rain gardens



Rhode Island receives 40 to 50 inches of rain a year.

However, during the growing season, there can be periods of little to no rain, causing plants to suffer from drought stress and many of us to reach for the sprinkler.

How do we know we are applying the right amount of water?

5” rain gauge with 1” watering gauge for measuring irrigation sprinkler output.

What is a rain gauge?
Where to place a rain gauge
Using a rain gauge
Measuring sprinkler output
For more information - water wisely

What is a rain gauge?
A rain gauge is one of the most important tools in your home landscape. With it, you can properly manage lawn and garden watering. Summer showers are often spotty and unpredictable. The only way to know how much rain we’re getting is to measure it using a rain gauge. While drought stress can impact plants, over-watering creates many concerns such as:

  • Increases risk of pollution from yard and garden care products.
  • Wastes valuable water and impacts water supplies.
  • Encourages shallow root zones and increases plant susceptibility to disease.
  • Wastes time and money – it costs money to irrigate.

A rain gauge measures rainfall and other precipitation events, such as heavy dew and mist. Most lawns and gardens need about one inch of water each week. By measuring and recording rainfall, you will have an accurate account of what nature has already supplied. Irrigation should only be used to make up the difference, and it should not be set to an automatic schedule.

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Where to place a rain gauge:
Rain gauges should be placed in an open area away from trees, buildings, and other structures, as this may cause an inaccurate reading. A general guideline to follow is placing the rain gauge twice as far away from the height of an object such as a tree.

Depending on the type, it may be made for mounting on a post with a screw, stuck into the ground with a plastic or metal spike, or stand on the ground with a special holder. Some holders are specially designed to add decoration to the garden. Check with your local garden supply or hardware store.

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Using a rain gauge:
After installing a rain gauge, you will need to check it once each day and record the amount of precipitation collected. If you do not check your rain gauge at about the same time each day, evaporation could occur and result in an inaccurate reading. Be sure to take the reading at eye level to avoid error and to empty the rain gauge after checking it.

Add the daily precipitation measurements at the end of each week to obtain a weekly precipitation amount. If the total weekly precipitation is less then one inch, the difference can be supplied with irrigation. Before irrigating, check the weather forecast and for signs of drought stress in your lawn or garden. For more information on proper watering refer to the Water Wisely factsheet.

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Measuring Sprinkler Output:
The 1” watering gauge can be used to collect water from your sprinklers so you know how much water is being applied. You can also use a bake pan or shallow can such as a tuna can if you do not have an extra rain gauge or special watering gauge. Place your watering gauge or can within the wetted path or radius of the sprinkler just prior to watering. Avoid placing at the extreme outer edge of your sprinkler’s wetted path.

When watering is complete, read and record the water collected in the gauge. If using a pan or shallow can, take it to a flat surface and measure the depth of water with a measuring stick.

Here is an easy way to calculate sprinkler output:

  • Run the sprinkler system for 30 minutes.
  • Measure the amount of water collected in your watering gauge, pan or shallow can.
  • Multiply that depth by 2 to get the amount of water that your sprinkler applies over a one hour period.

Adjust the flow rate and running time of the sprinkler to apply the amount of water intended without causing runoff.

For example, your sprinklers ran for 30 minutes and you collected ¾” of water. Multiplying ¾” by 2 equals 1.5 inches over a one hour period. You thought you were applying ½” over 30 minutes, or 1” over a one-hour period.

Next time you irrigate, you can reduce the flow rate (gallons per minute) as needed to result in ½” over 30 minutes or 1” over a one-hour period. You can figure this out through trial and error. If the flow rate is set and not contributing to runoff problems then simply reduce the running time. For example, you could reduce the watering time to 20 minutes and then measure again to see if you are now at ½”.

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For more information about water conservation:
View our Water Wisely fact sheet