The following article states the following for changes to Management allowed depletion (MAD):
Increasing reduces run time
Decreasing increases run time
Increasing the % increases watering frequency
Decreasing the % decreases watering frequency
When I change my Zone (using Advanced Settings) value for Allowed Depletion percentage, the Schedule reflects the opposite of what the article describes. In my case, increasing Allowed Depletion (e.g. was 30% and I increase to 35%) significantly increased (Watering Duration minutes) Run Time.
Am I doing something wrong, or is this article wrong?
While I’m sure I’ve looked at that article a dozen times, my understanding, as well as your experience, is just the opposite.
Increasing MAD allows the total soil moisture to become lower before watering, and will definitely water more (in direct ratio to the MAD) when it does water, because it will make up that deficiency in one watering, and to increase water, the time will increase. And, given that the other factors remain the same, watering can occur slightly less often, because more is applied each time.
Assuming we’re right, how could no one have noticed this previously (I’m asking myself)?
(This assumes Management Allowed Depletion is the same as Allowed Depletion in the Rachio program)
@laura.bauman Could you have staff look into this documentation? I just plunked a higher MAD into my spreadsheet that tracks to your watering time calculations, and yep, increasing the MAD INCREASES the run time, and decreasing it DECREASES run time. I think the doc is wrong.
@bradphi Dane here with Rachio Support. Thanks for bringing this to our attention (+ @Linn for flagging us) ! That information was incorrect and we’ve updated it. @rraisley It was not always like that. While I cannot be 100% certain I believe this error occurred when we were updating articles over the winter. Likely a copy/paste error. It’s embarrassing but, I’m glad we’ve got it fixed thanks to you all.
@bradphi@rraisley has a good write up above. I’m curious, are you adjusting allowed depletion specifically with the intent to control the duration of the zone?
If possible, I like to leave Allowed Depletion at 50%. I’ve dropped it down for one zone in my front yard, because I seem to get more runoff than I like. And I’ve decreased it on my shrubbery zone because I like it to water a bit more often.
In general, AD is sized to give you the maximum water at one time without running off or puddling. To high will, well, run off or puddle, too little may not water often enough, all other things being the same.
I personally don’t like to mess with AD much if there is any adjustments needed. I leave that to Crop Coefficient, or even root depth…root depth is easier for me to grasp…shallow roots need shorter more frequent watering, deeper roots need longer less frequent watering.
As I mentioned, I do normally keep AD at 50%. Changing Crop Coefficient is entirely different, as it determines how much water is applied over time (like per week), rather than at one time. And yes, changing root depth works just as well as AD and can be more visual.
For my lawn I leave AD at 50%. But for the drip lines on my perennials/annuals, I found I had to adjust it to 25% to keep the annuals from wilting in the heat of the summer and make sure the system waters often enough… Because I have a mix of perennials and annuals in my drip lines/zones, I’ve had to tune to the annuals. And doing that, I’ve found that the perennials do just fine.
I’m going to try 25% for my peppers and tomatoes. I’ve been using a fixed schedule for the above reason but that is not ideal. Fixed schedule saturation skip isn’t transparent enough for me.
Confession time… I’ve been very nervous to “trust” anything near to 50% Allowed Depletion (afraid I’ll underwater here in Phoenix). With the encouragement from all of you on this thread, I’m testing changes as below.
To summarize (as of 4/24/2021 with 88-90F high today):
BEFORE adjusting was 166 minutes every 4-5 days
AFTER adjusting is (WOW) 309 minutes every 8 days. (I chose “Reset to Default” for this zone, and manually kept Nozzle Inches / Hour at 0.45)
Do the AFTER watering times and frequency look too extreme for the Phoenix area? @tmcgahey since you’re in AZ might have some insights
Details below…
Trees Zone:
Primarily Queen Palms, a few younger (7 years) Ash trees, and a newly planted Indian Laurel (decent size from nursery in 36” box).
SETTING
BEFORE
AFTER
Available Water
0.18 in/in
0.17 in/in
Root Depth
25 in
25.59 in
Allowed Depletion
26%
50%
Efficiency
90%
90%
Crop Coefficient
90%
75%
Nozzle Inches / Hour
0.45 in
0.45 in
Automatically Determined Watering Time
166 minutes
309 minutes
Automatically Determined Watering Frequency (above avg temps in Phoenix 88F high today)
… and here is the Spray Head type… believe these emit less than the App’s option of “Bubbler” which is why I’ve set Nozzle Inches / Hour at 0.45.
I really think Rachio’s default root depth for trees is overly optimistic, especially if the trees are young. I like 12” as that’s where most roots will be for most of my trees. Anyway, as summer comes you should find the watering frequency increasing. Keep an eye on things and adjust as needed. There’s no autopilot until you’re done tuning to what you observe.
You can easily test your hypothesis by measuring how much water gets into a container within a period of time extrapolated to an hour like a catch cup test but for bubblers. You may be surprised just how much water those can emit! Also keep an eye on them. They like to adjust themselves closed
Those kinds of spray heads are going to put out WAY more than .45" per hour. Do you have a manufacturer on those?
I’d also agree that when starting with Rachio, bring the root depth of trees up to 18" or so. This will cause it to water a little less each time, but more frequently. Chances are your previous watering wasn’t promoting overly deep root growth. Watch the new stuff closely as we head into summer. Might take some supplemental watering either through the app, or preferably via a hose to keep it happy as the roots get established.
But otherwise, no, I’m not surprised by long watering cycles. My tree zones run for almost 4 hours at a time, and my shrubs just over 3. Just make sure your system is working well and no leaks. 4 hours with a leak can be bad news!
