The Irrigation Water Management Society
Certified Site Water Planner (CSWP)
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|Get daily updates when the Irrigation Index changes, and/or get weekly updates of the watering forecast:|
Find out how much water your lawn needs in real time! Get irrigation requirements and see up-to-date weather data for your area from the Puget Sound Weather Stations.
Use the Water Budget Calculator to determine how much water a lawn
needs, based on the size of your irrigated landscape and yearly weather
averages for the Seattle area.
Use the Sprinkler Scheduler to create watering schedules for automatic in-ground irrigation systems, based on the types of your plantings and watering system.
ET (Evapotranspiration Rate) is how much water your plants use—thus, how much water you need to replace to keep your landscape green. Watering more than this is a waste of money and water.
Users who need access to weekly raw ET/rainfall data in CSV format can download the data by clicking here.
|Average ET, Actual and Effective Rainfall and Irrigation Index (for the irrigation season)|
|Month||ET||Actual Rainfall||Eff. Rainfall (33%)||Irrigation Index|
Year to Year Water Use Comparison Chart
How did plant water use (ET) in 2012 compare to the average for the Puget Sound area?
The table below shows how much water your plants used (ET) in 2012 compared to the average.
Plant water use was down 4% in 2012 compared to the average.
|Month||Avg. ET||2012 ET||ET Diff.||ET Diff. %||Avg. index||2012 index
|Changes in plant water use (ET) as compared to the average*|
|Up 5%||Up 11%||No Data||Down 4%||Up 6%||Down 5%||Down 9%||Down 4%|
|*Data rounded to nearest whole number|
As with most technology, weather stations and the technology that ties it all together, are sometimes victims of malfunctions. Occasionally the weather data produced and posted on this site might be temporarily inaccurate. Please check the data being used for obvious errors. (for example: if the ET one day is .13" and the next it is 300" then caution is advised)