The @theflexdude be like…
3 Likes
Question for the gurus, I need my memory refreshed (or maybe expanded), too. Does the amount watered always equal the full amount to replenish the root zone from allowed depletion, or can it vary depending on previous day moisture level, and expected precipitation for the irrigation date? In this example, if the watering was done early in the day, that it would have brought the zone up to 100% with the 0.53, then some ET later in the day dropped it some.
I notice that in V3, when looking at moisture levels, it includes recent watering, so I am thinking the duration is more dynamic than in V2.
@jkb We always water for the entire depth of water, unless the day of depletion is restricted. In that case we water the previous non-restricted day for amount that is enough to fill the bucket including ET for the day. So during normal watering you will have (Previous balance + precip + depth of water - ET) as your end of day balance. On restriction fill up you will have depth of water as your end of day balance and irrigation amount will be computed as the following: (watering amount = depth of water - precip + ET - previous balance).
1 Like
So when the zone runs for 43 minutes instead of the recommended 70 (I think it really should be 77 minutes) and the graph shows .66 inches of water instead of a fraction of the amount, can you see where this draws confusion?
The graph tells me that .66 came from flex (the + sign).
So I’m back to the question: am I required to have my flex schedule to run for 70 minutes to actually get the .66 inches of water that the graph tells me I got?
Where are these constants coming from?
Also, am I wrong in thinking that a system with a pr of .64 with efficiency of .8 requires 77 minutes to reach .66?
.66 / (.64 *.8 / 60) = 77.34
This has been confusing me too. I’m coming at this a little differently, with a little less math, but I’m wondering if I’m starting to see a little of what is going on.
@plainsane , did you by any chance tweak your duration times on the previous version of the software? The comment
makes me think that you did.
Here’s what I’m seeing after playing around quite a bit this morning.
My zone 5 and zone 6 are set up identically. Last year I had problems with them getting too much water. They are in an area of my yard in mostly shade that just does not drain well. And the zones overlap. So last year I did a duration tweak of 65%. Under the old software, that tweak made the system THINK it was still putting down the .61 inches which was supposed to have a watering time of 45 minutes. But I was only watering for 30 minutes.
Here’s the weird thing I’m seeing now. I think that my 65% duration tweak from last year is still in place, and I can’t get it back to 100%. I set up a test phantom zone (zone 13) IDENTICAL to my zone 5, and it calculates out that it will water for 45 minutes. Went back to my zone 5 and changed characteristics (I was playing with root depth) to make sure I could see the duration changes. But when I make my zone 5 and my zone 13 exactly identical again, zone 5 wants to water for 29 minutes and zone 13 for 45 minutes. That 29 minutes is 65% of the 45 minutes. Which seems to me that it’s keeping my previous tweak (only it no longers tell me that I had tweaked it or what that tweak was).
Luckily, I keep track of all my zone settings (and changes) so I at least know what duration tweaks I had set.
But had I not recorded those tweak percentages, I wouldn’t now know how to change the durations to get them to what the schedule recommends. @plainsane, I think this is part of what is throwing you off.
And I did actually like that tweaking the duration time was a way to shorten watering time without getting into all the increase/decrease frequency/watering amount since I was having such a hard time with this area of my lawn.
I’m pretty sure the answer to this is yes.
I did my calculation slightly differently than @theflexdude did, but using the scheduling multiplier I also came up with approximately 70 minutes.
My calculation to come up with watering time:
Available water * root depth * allowed depletion = inches to water
((60 minutes * inches to water) / pr rate) * scheduling multiplier = minutes to water
((60 * .66) / .64) * 1.14 = 70.53
That’s precisely what user modification to duration does. It tells the system “this is how long a user thinks it takes to reach the depth of water for that zone”. @plainsane as @Linn quoted there is a 62.2935346861727% adjustment to your durations that is shortening the watering interval.
The easiest way to get to 100% is simply to delete the schedule and create a new one. All of your moisture levels will stay but the durations will be the ones recommended.
1 Like
Scheduling multiplier is applied to adjust for non-uniformity in turf applications. Because the systems are not perfectly uniform, it’s a standard practice increase the run time in order to minimize dry spots. 0.4 and 0.6 are constants used for all calculations. So if we invert the moisture level formula for duration for entire depth of water, we have:
duration = depthOfWater * schedulingMultiplier * runtimeAdjustment / precipRate
For recommended duration runtimeAdjustmentCoefficient is 1.
depthOfWater = 0.66 in
schedulingMultiplier = 1.14 (based on 80% efficiency)
precipRate = 0.64 in/hr
Hence,
duration = 0.66 * 1.14 * 1 / 0.64 = 1.1756 hours = 70.54 minutes
With runtimeAdjustmentCoefficient = 0.622935346861727 (user duration adjustment) we have:
duration = 0.66 * 1.14 * 0.623 / 0.64 = 0.7324 hours = 43.945 minutes
1 Like
At least for me, I just logically thought that the efficiency percentage would be applied against 100% of the base precipitation rate. What is interesting is that it’s only applied against 60% of the precipitation rate (the .6 part of the scheduling multiplier). Obviously, someone is way smarter than me when it comes to this!!!
@theflexdude, thanks for posting these calculations! This answered some of my questions from previous years!
2 Likes
I want to get this straight…using this formula above, if I lower my flex schedule to 5 minutes, that gives me a runtime adjustment of:
= 300 / 4217
So we plug that into the next equation
0.65993740219092331773 = 5 *(0.64 / 60) / (0.07114062129475930756 * 1.136)
And now we are getting to the crux of my issue…the screen shot below shows a 5 minute run for a flex zone (every zone attribute is equal). I think you will see 2 things. First, moisture from the manual run is recorded in 2 different ways. The sum total which is .05, I agree with this number. The second total is attributed to a manual run, at .08, I disagree with this number, but let’s ignore that, you’re telling me that it is appropriate to adjust the moisture balance in 2 different ways with all things being equal except for the triggering event?
The model is fundamentally broken, accounting for the fraction of runtime on both sides of the equation causes it to becomes idempotent, if you change the equation to:
0.04694835680751173709 = 5 * (0.64 / 60) / 1.136
You remove the idempotent behavior of the runtime fraction on bothe sides, push it left, AND you still account for efficiency on the right, this number also lines up with the accounting for a manual run. So which accounting method is correct?
This used to not work that way, sad panda.
@plainsane Applying 5 minutes to the formula with runtime coefficient gives
5 *(0.64 / 60) / (0.622935346861727 * 1.136) = 0.075 inches
without coefficient
5 *(0.64 / 60) / 1.136 = 0.0469 inches
In your case the moisture applied should have been 0.08. So looks like we have a defect where we incorrectly compute the total but the breakdown shows correct value. We will have that fixed today. Thanks for showing this to us!
3 Likes
The fix for irrigation totals has been released.
3 Likes
Thanx for the fix.
I meant if I adjusted my flex to run for five minutes. Like on this zone. A zone with all of the same attributes, just a 5 minute schedule.
So really, what I have learned is the pr and efficiency are superfluous to flex. You could actually do away with those without any impact to the system.
Why not just just compute water needed, which is .66 (notice no efficiency or pr there, just awc, root Depth and awd)
Divide that by my schedule run time which is 43 minutes to get a pr rate by the minute of 0.0153488372093023 The multiply it by 5 minutes, same answer, boom 0.075 inches, as you report.
Multiply it by 43 minutes, boom .66 inches.
So thanx for taking the time to humor me, the flex algorithm, I thought it to be something else.
We need a runtime as a base. A sane value corresponding to the settings. Without it we cannot determine the moisture/minute irrigation rate. Once you have the base duration, then it is trivial as it should be. That is what we use the PR for, which is essential to give an estimated duration.
1 Like
Yea sorry if I wasn’t clear, that is what I finally understand, runtime is the base not pr, nor efficiency.
Yes, but in order to compute runtime you need PR and efficiency.
Well, your just computing an informed suggestion, you can’t even call it a base line. I can change the duration of the zone and the graph doesn’t change ever, at all, just the amount of water that actually goes on the yard.
I mean I kind of get it. You don’t expect ppl to change those settings, but it’s ultra confusing…
Edit:
Sorry, it’s not a suggestion, I understand that the runtime computed at schedule creation., I misspoke