Where do the numbers (0.4 and 0.6) in the scheduling multiplier come from?
SM = 1 / (0.4 + 0.6 x DU), where Distributed Uniformity is Efficiency in Rachio
There’s another suggested SM, which is:
SM = 1 / (0.352 + 0.72 x DU)
Are they numbers that were produced based on water movement in soil horizontally and vertically?
I think they’re both WAGs (Wild A$$ Guesses), trying to water extra for inefficiency, but not /that/ much extra. Basically, it dilutes the value of the Efficiency calculation, to prevent using too much water.
Since, in this case, Efficiency is defined as the Average of the lowest 25% of Readings divided by the Average of All of the readings, it’s already given that using Efficiency is not going to provide 100% desired water to the lowest catch cup reading areas.
I personally think efficiency isn’t worth bothering with; you can calculate the average water applied to a zone, knowing it’s not all that even. Plus some of the time areas not watered much by sprinkler heads get runoff from other areas. If some spots remain too dry and don’t do well, you have to increase the time. Regardless of the efficiency.
I think it’s a bit amusing to calculate times to the minute, making 1% or 2% variations in adjustments, when 90% of the users don’t know the actual Nozzle Flow within 25% or more.