Watering Index

What does it do?

The Watering Index is an easy, simple and free method of matching your irrigation controller to your plants’ actual water demand.

How does it work?

Throughout California there are weather stations that measure the water demand of the plants for the actual conditions of the day. These weather stations are called CIMIS Stations. CIMIS stands for California Irrigation Management Information System and farmers use these stations to know when and how much to water their crops.

The Watering Index is a percentage based on the maximum amount of water you should apply to your landscape. Residents, gardeners and landscape maintenance professionals can easily use the Watering Index to make sure the plants they care for are getting the right amount of water. Check the Watering Index weekly and adjust your watering to match the current index value.

The index is normally 100 percent for much of July and August. Over the course of the year the index changes to reflect the landscape’s changing need for water as climatic conditions change.

Think of it this way: during a hot, dry week in July, you are watering at 100 percent of your landscape’s maximum needs. During June gloom, you may only need to water half as much. Check the web site for the current watering index.

So what do I do?

Your irrigation system needs to be in good working order. That means your system has no leaks, no mismatched parts and is watering the intended plants. Visit www.santaclaritagardens.com to view common irrigation challenges and solutions.

How to Set It Up
  1. Step One: Check to make sure your plants are healthy and your irrigation controller is watering properly. Visit www.santaclaritagardens.com for sample irrigation schedules. Once your schedule is correct, proceed to step two.
  2. Step Two: Make sure that the schedule in your irrigation controller is set for the summer. Even if it is winter when you are doing this, you need to use the summer schedule. Why? Because the index is a portion based on the summer schedule!
  3. Step Three: Select the Watering Index function so it displays the current index or percentage. It should show 100. If it does not, STOP. Go to the section marked CORRECTING YOUR SCHEDULE.
  4. Step Four: Adjust the number in the display to the Watering Index number you found on www.clwa.org. Some clocks will only let you change the percentage in values of 5 or 10. If that is the case, round up.
  5. Step Five: Check back at regular intervals and change the index number. It’s easy, just turn the dial to the index and adjust it up or down to ensure your plants are getting just what they need. TIP: Put a reminder on your calendar or check the percentage the same day your trash is picked up.

Congratulations! You are now following the watering needs of your plants with your watering schedule.

Why Is Weekly Adjustment Process Important

You can save a considerable amount of water by adjusting your controller via the Watering Index. Reducing your water use will reduce your water bill and help us save a very precious and limited resource.

Correcting Your Schedule
  • My Index shows less than 100 percent.
    This means that the irrigation controller is watering for less time than it is programmed to water. As an example: I have a station run time of 10 minutes but the Index shows 80 percent. Your actual run time is going to be eight minutes.
  • My Index shows over 100 percent.
    This means that the irrigation controller is watering for more time than it is programmed to water. As an example: I have a station run time of 10 minutes but the Index shows 120 percent. Your actual run time is going to be 12 minutes.
  • How do I fix it?
    Visit www.santaclaritagardens.com for sample irrigation schedules. Then be sure to set the controller to the current Watering Index you find on this website.

For more ways to ensure water efficiency, please check out more water saving tips.