In my area in Southern California, there is a govt. website that will supply daily ET values for a patch of turf in full sun from a station close to where I live. That will give me a good indication of how much water will be needed by the sunniest parts of my yard, but others have considerably more shade.

Is there any way to calculate, or figure out what the difference in ET would be based on relative amounts of exposure to full sun, given all other conditions are the same?

I need to redo my in ground sprinklers, and would like to set up the circuits to correspond to sun and shade as closely as I can. I would like to be able to figure an offset in run time- if the sunny circuits need .75", then the shade circuits will need X".

Is there anyway to do this? I could do it some real world testing, because I have two moisture sensors on my property, but I would rather not dig them up and move them around if there is already a way to do it mathematically.

Ian