Weather Center - ET

Can you say Evapotranspiration?

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 ET Hotline



Coastal, Central and Foothill weather station data is electronically transmitted daily to IRWD where it is used in a formula to calculate evapo-transpiration, also known as ET, which is the amount of water needed by turfgrass to remain healthy in each specific climate zone. Outdoor watering accounts for 40 to 70 percent of water used in Orange County. With thousands of acres of valuable community parks, gardens and greenbelts within its boundaries, IRWD's billing system relies on accurate weather station data to provide landscape and commercial customers like you with site-specific allocations to ensure that your landscaping receives sufficient water.

 Important Links

 Weekly ET Allocation Data

 CIMIS Information

 Year-to-Date Daily ET

 Weather Station & Microclimate Map

  Historical ET Data






















 Weather Determines Your Allocation

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How Weather Affects your Water Allocation:
When the weather is hot or windy, your allocation goes up automatically. When it's cool or rainy, your allocation decreases.

Staying with Allocation Makes Sense: The goal is to allow you the correct water allocation you need for your landscape to stay healthy and attractive. Using more water than plants need is a waste of water, a waste of your money, leads to unhealthy plants, and can contribute to pollution-causing urban runoff.


 Weather Station Technology Helps you Save Water

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Advanced Weather Station Technology:
IRWD uses the most advanced weather station technology, consisting of Campbell Scientific CR-10X Data Logger equipment, the same used by the California Department of Water Resources for the 100 California Irrigation Management Information System stations around the state.

IRWD has 3 Microclimates: Within our service area, there are three distinct microclimates, known as the Coastal, Central and Foothill zones. IRWD maintains a separate weather station in each climate zone to monitor exact wind and weather conditions, including air temperatures, relative humidity, precipitation, solar radiation, and wind direction and speed.


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