The Daily Irrigation Index and Weekly Watering Forecast
Sign up for the email updates and receive the Daily Irrigation Index only when it changes and the Weekly Watering Forecast on Monday mornings.
Note: We will not share your email address. Email service will end Sept. 30.
Yesterday's ET ( ):
Evapotranspiration (ET) is the amount of water that evaporates from the soil and transpires through a specific kind of plant material.
The Irrigation Index :
Use the Irrigation Index to adjust irrigation runtimes with the “Percent Adjust” or “Water Budgeting” feature found on most sprinkler controllers. The Index is a percent of the typical "peak" watering period, when days are longest, the weather is hottest and the Index is 100%. The percentage is adjusted daily based on actual weather conditions.
The Weekly Watering Forecast :
The Weekly Watering Forecast is designed for a single weekly adjustment to irrigation runtimes. Updating every Sunday night, the forecasted index is based on the actual evapotranspiration (ET) of the previous week combined with the average considtions for the same period from past years.
About our website
IWMS provides simple tools to improve the efficiency of automatic irrigation systems. Brought to you by the Saving Water Partnership and Seattle Public Utilities.
Irrigation Controller/Clock Water Saving Features & Tips
To help save water and keep plants healthy, learn how the water saving features on common irrigation controllers work.