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How to calculate how long to irrigate

You understand the reason for water awareness and conservation. You’re diligently following the Defined Irrigation Schedule adopted in 2013 for the 10 MUDs served by The Woodlands Joint Powers agency. You receive the WJPA’s weekly irrigation recommendations, and you want to follow those too.  (If you don’t receive the weekly email, you can sign up at wjpa.org.)

But the question remains: how long should I water to put 1” of water on my lawn? How long will it take to put ½ inch? After all, water pressure may vary, different types of sprinkler and rotor heads put out different volumes of water, and other factors may contribute to variations from household to household.

There are some sophisticated logarithms available, but unless you’re an engineer, you might have trouble applying them.

Don’t despair…there is an easy way to find out how much you are watering.

  1. Evenly space six or more straight-sided food containers (tuna cans, cat food cans, even small rain gauges) across a zone.
  2. Run your sprinkler system for 15 minutes.
  3. Measure the water in each can with a ruler.
  4. Add up all the measurements and divide that number by the number of cans. This will give you an average amount of water the system is putting out for 15 minutes.
  5. Multiply the average by 2 (15 minutes X 2 = 30 minutes). Round the final number out to the nearest ½ inch.
  6. This will give you an idea of how much water your sprinkler system is emitting in a half hour.

How to comply with the recommendations and still have a healthy lawn:

  1. If the recommendation is one inch per week, then water one-half inch on each of your Defined Irrigation Days.
  2. If the recommendation is ½ inch, water ¼ inch on each of your DIS days.

If you have a programmable controller, then water each zone twice (cycle and soak method) each prescribed day for the same amount of time as shown in the chart.chart (002)

The Woodlands Joint Powers Agency
2455 Lake Robbins Dr
The Woodlands TX 77380


855-H2o-SAVE (855-426-7283)

Hours of Operation:
8:00am to 5:00pm Mon-Fri

For Emergency call
855-H2o-SAVE (855-426-7283)





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