I was struggling to find a way to convert my dripping emitters to inch/hr precipitation rate. I found this article: Calculation of Precipitation Rate (PR) of Drip Emitters and Bubblers ...
Conceptually, PR = gph / root_area for one tree. For root area, maybe critical root area can be used? What is the Critical Root Zone around a tree?
I feel this is an intuitive way to calculate PR. Of course, root area is a little hard to get right.
