Evapotranspiration Variation vs. BOM

Hi Team,

I am located in Brisbane, Australia and I have my Rachio hooked up to a local PWS located only 1 km away. I am puzzled as to why my crop evapotranspiration levels (on my Rachio) are half of what the Bureau of Meteorology (BOM) is publishing for my area (0.7cm). The result has been that my lawn is drying out before the Rachio starts the irrigation system. I have flexible day schedule activated and 3 zones setup. This discrepancy is happening across all of my zones. My grass is buffalo grass. What changes to my setting can I make to adjust for the difference in my crop evapotranspiration (Rachio published 0.4cm vs BOM published 0.7cm). Your help would be greatly appreciated. Cheers, Robert.

I didn’t know anything at all about buffalo grass and just did a little reading on it. Pretty amazing grass! But I’m wondering if decreasing your root depth would help. I read in a couple of places that 70% of the roots (by weight) are in the first 15cm. I would try changing your root depth to maybe 30cm (or maybe even less) and see if that helps. That would definitely get flex daily watering more often.

That really doesn’t answer the crop evapotranspiration question, but I think it would be worth a try.

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@GroundedCopilot - I believe increasing the crop coefficient will increase Rachio’s evapotranspiration values. The suggested method is to move in small increments - e.g. .1 and observe the behavior.


i had buffalo grass for first ten years. Residential property built on half acre. Works as advertised: thrives on neglect, including no watering during hot summer months (turns brown) and no fertizing.

Later, we gradually got rid of it. Trees we planted eventually provided too much shade - buffalo grass absolutely does not grow well in anything except full son. And secondly, we got concerned about fire danger. In the summer, with no water (doesn’t need it), it turns nice and dry and brown.

If you have nothing but sun and it will always be full sun, and you don’t mind the fire hazard or it’s such that it’s not a fire hazard, then it’s an exceptional grass for hot climates.

I have one zone that’s still buffalo grass. My Iro2 settings result in much less water for this zone than any of my other zones. Absent rain, in the summer, I go about 4 weeks in between watering.

Best regards,


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Please se your crop co to .77, that should bring things close to alignment.

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Thank you everyone for you words of wisdom. I am working through each of your suggestions and I am starting to notice a postitive change in my lawn. I will keep you all posted.