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The Watering Index and Watering Calculator

California is in a serious drought.  Southern Californians need to reduce water use to maintain the region’s water supply reserves.  One of the most effective ways to conserve is by limiting landscape irrigation.  Up to 70 percent of residential water use is applied outdoors.

Many communities have mandatory watering restrictions that limit the days, times and duration that customers can water their landscapes.  These regulations vary across Southern California. 

Check with your local water provider to find out the watering days and times allowed in your area.
The following tips will make your lawn and shrub watering more efficient:

  • Enable plants and trees to grow deep roots that help them withstand drought and longer periods between irrigation. 
    • Water less frequently and at a slower rate to allow the water to percolate deeper into the soil. 
    • Apply water more slowly by installing multi-stream rotating nozzles on your sprinklers, or convert to drip or hand watering.
  • Eliminate run-off.  If needed, use multiple start times with shorter durations (“cycle and soak”) during the allowable watering period to avoid water waste.  Be sure not to exceed the maximum allowed minutes of irrigating per day.

Using the Watering Calculator during Drought and Watering Restrictions

IMPORTANT:  The Watering Calculator tool estimates the correct amount of water to give your landscape or garden every week during normal supply conditions. Developed by the city of San Diego, it provides customized watering schedules by zip code based on data from the California Irrigation Management Information System (CIMIS) weather station network.  The calculator uses average numbers for weather, plants, and soils within zip codes of the urban Southern California area. These are only suggested run times, so you will need to observe plant health and/or soil moisture levels and make adjustments as necessary.

The Watering Calculator is not adjusted for drought conditions or watering restrictions and should only be used as a guide.  Local watering restrictions are intended to help conserve water across a broad range of conditions, and the limits on watering will differ from the calculator’s results.  In situations where the calculator indicates that less water is needed on a weekly basis, customers should adjust usage to meet the plants’ needs and allow deep rooting but not exceed the maximum allowed minutes per day.


How to use the Watering Calculator:

  • Answer the questions below for each yard area. You can create a watering schedule for up to 6 areas at one time.
  • When complete, click on the button below to see your customized watering schedule.


1. What is your zip code? (Only zip codes within urban Southern California are included.)
2. What would you like to call this landscape area? (front yard, citrus trees, etc)
3. What type of plants are you watering?
Look here for examples of Grasses, Ground Covers, Shrubs, or Trees )
4. On this scale from Sandy to Clay, how would you describe your type of soil?
Sandy Loam
Clay Loam
5. What type of watering system do you have?
Sprinkler* Micro-Spray*  
Impact Rotor* Drip  
Gear Rotor*  
*If you are using a Sprinkler, Rotor, or Micro-Spray, and you know your application rate, please enter it here:

watering calculator

watering index
IMPORTANT: The Watering Calculator does not reflect local mandatory conservation measures that may be in effect because of the current water supply shortage. Please check with your water provider to find out what watering days and times are allowed in your area.