I have read many of the manuals on the calculations of the RM. Everything seems great, but not for those of us where QPF is calculated high everyday, but there is no rain (Why does this happen? not a fault of the developers for the RM). This is seen on many post by others. I have been also trying to deal with it - as programming the RM should be a breeze.
The soil I have is 'Silty-Loam' which does not hold much water and the grass has difficulties getting the roots to any depth to get the water that is there. I have slightly adjusted the 'Vegetation' type to try and compensate. Water run-off happens at a very low water volume.
Situation - 90-95 degree heat for multiple days: Watering set to even days as per the city.
No rain in the forecast, the system runs great, around 110 to 120% - but no rain predictions never happen. It had for about 7 days and this is where I fine tuned the system.
Situation 1 - QPF is predicting over 1.00 inch of rain on the odd day following the next set watering scheduled day. Still 90+ degrees 'ET' higher than normal. RM does not water as rain will come tomorrow. It does not rain. Watering for the next even day is set for over 180% by the RM. Would go higher but I stop it there. By the time it waters, grass is not good, but it will survive and come back. Four days between waterings. RM works as designed and compensates for the situation. The end result is not the best as the lawn does not look well at the moment but should come back fine.
Situation 2 - Same as above but on the next watering day, the odd day following the day of watering also has a very high QPF, so the system does not water again. Now it is 5 days without water - lawn is getting bad. Guess what - it did not rain. Now 6 days of over normal 'ET' - lawn is now shot, I will never get it back without tender loving care. Watering more than twice each even day as to get the soil back for the vegetation.
The soil I have is hard/compact - the water is deeper as the roots of the lawn can not get to it.
For the above I have compensated by setting the 'Rain Sensitivity' down to under 30% - this effects the QPF prediction and also the calculated amount of water entering the soil. Example - if it does rain 1.2 inches at 30% setting the soil will not hold any more water, but the system will state only 0.4 inches due to the same control setting. In this case, it does not water but will water again to quickly after the rain due to incorrect absorption settings. I adjust the soil? Tried that, been there, catch 22.
It would help out greatly if this one control did not do both settings. I can also see how it does, as it is calculating the QPF absorption used in both areas of the calculations.
Anyone else see a need for this?
Or - the other thought is for 'Prediction of weather forecasting' to not use future QPF, as a switch to turn off and only use ET calculations. This way the soil absorption would still be controlled by 'Rain Sensitivity' and with 'Forecast Correction' the system could then use QPF as actual and make adjustments due to rain after it has happened.
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