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Lawn Care — Calculate Watering Schedule

Watering Your Lawn - To properly water your lawn, you must first determine the precipitation rate and uniformity.

How to Measure Your Precipitation Rate

To measure your precipitation rate and uniformity, place a grid of equal sized containers around your lawn as shown in the photo. It is best if you use containers with vertical or near vertical sides. You should also take measurements at the same time of day your sprinklers normally operate. This will reduce errors from variation in water pressure throughout the day. Measurements should be taken on a calm, windless day.

To Determine Your Precipitation Rate and Uniformity:

  • Evenly place measuring containers on lawn, using a minimum spacing of 10 feet.
  • Turn on your sprinkler system for 15 minutes
  • Turn off your sprinkler system
  • Keep measuring containers in place
  • Measure and record the inches of water in each container
  • Note the containers with the lowest and greatest amount of water.



If the difference between the lowest and greatest amount in the containers is more than twenty percent, it indicates an inconsistency in your irrigation pattern. Adjust wet areas to receive less water and dry area to receive more water until your lawn is provided with a consistent pattern of irrigation. If you're unable to adjust your sprinkler system to provide a consistent pattern of irrigation, you may need to add or change sprinkler heads, or call a landscape professional.

Calculation of Precipitation Rate

Take the measurement from the container with the least amount of water and multiply by four. (i.e. 1/2 inch x 4 = 2 inches per hour). This is your hourly precipitation rate. Use this number to determine your watering requirements. Be sure that you are providing a uniform irrigation pattern to your lawn as described above.

Note: Precipitation rates are typically greater than 0.25 and less than 2.5. If your calculations are outside this range, we suggest that you check your calculations to ensure you have computed the correct rate.

Enter the hourly precipitation rate you've calculated: