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ET (evapotranspiration) is the water evaporated from the ground back to the atmosphere both as transpiration from the leaves of plants and also as direct evaporation from open water and soil.


Reference Evapotranspiration is defined as "the ET from an extensive surface of clipped grass (ET_o) or alfalfa (ET_r) that is well-watered, and fully shades the ground." (Kimberly R&E Center, Univ. of Idaho)

Help CoCoRaHS measure ET_o!  We know how much water comes from the sky (precipitation) since many of us measure it.  Knowing how much water is leaving the soil and returning to the atmosphere is just as important.  It matters for agriculture, lawn care, weather prediction, hydrology and much more, so we should try to measure it.

Interested in becoming a ETo observer?

Some things to consider as you apply:

1. We are looking for "ideal" locations (open exposures with surrounding vegetation that is representative of your area) and highly motivated observers (you have reported on a consistent daily basis for CoCoRaHS over time).

2. You are up for the challenge of taking on a more complex daily observation.

3. You or a sponsoring organization are willing to make the substantial investment in purchasing this delicate instrument, the ETgage ($239.75 plus tax and shipping from weatheryourway.com ).

Still interested?
Please contact Noah at info@cocorahs.org with a photo of the site where you will install the gauge and he will follow up with you.