Irrigation Question(s)

[MWareman]

I understand that the daily ET is calculated only once a day - is it based on the prior day's actual stats?

 

From the Wiki:

I'm reading http://wiki.universal-devices.com/index.php?title=ISY-99i/ISY-26_INSTEON:Using_the_WeatherBug_Irrigation_Module and trying to understand the irrigation module with Weatherbug stats.

 

"Yesterday's Water Deficit - total amount of water that has evapotranspired during a twenty four hour window from the day before."

The way it's written - this is calculated at the end of the day and then fixed thru the next day - ignoring any ET that happens since - or any rain that falls after the calculation, but adjusting for any rain that fell during the prior day. Is this the case? I seem to have a -ve deficit at the moment - so I assume that simply means it rained more yesterday than was lost to evapotranspiration.

 

"Irrigation Requirement - amount of water to be applied based on the accumulation of previous day(s) water deficits."

So this is just a running total of deficits? I assume this is only calculated once each day - and ignores any rain that falls after the calculation - or any ET that happens during the day. Is this correct?

 

By example, today.

 

Irrigation Needs 2013/05/03 at 04:00:00 is 0.3625 inches

ET is 0.1006 inches/day.

Yesterdays deficit is -0.0443 inches

Rain today so far is 0 inches

 

Irrigation Needs 2013/05/03 at 18:00:00 is 0.3625 inches

ET is 0.1006 inches/day.

Yesterdays deficit is -0.0443 inches

Rain today so far is 0.16 inches

 

It rained 0.16 inches between 4am and 6pm today - but the 'irrigation requirement' still shows 0.3625 now at 7pm. Shouldn't it have gone down?

 

I'm getting myself a little confused in that if it rains during the day (after the ET is calculated) but my cycle is triggered at 6pm - I seem to get a situation where the rain during the day is not assessed in determining if the 'Irrigation Requirement' threshold has been exceeded. Should I subtract 'Rain Today' from 'Irrigation Requirement' and see if that exceeds the threshold for irrigation at the end of the day?

 

What is everyone else doing?

 

Thanks,

 

Michael.

[IndyMike]

Hello MWareman,

 

You are very close on your understanding of the WB module:

 

I understand that the daily ET is calculated only once a day - is it based on the prior day's actual stats?

 

From the Wiki:

I'm reading http://wiki.universal-devices.com/index.php?title=ISY-99i/ISY-26_INSTEON:Using_the_WeatherBug_Irrigation_Module and trying to understand the irrigation module with Weatherbug stats.

 

"Yesterday's Water Deficit - total amount of water that has evapotranspired during a twenty four hour window from the day before."

The way it's written - this is calculated at the end of the day and then fixed thru the next day - ignoring any ET that happens since - or any rain that falls after the calculation, but adjusting for any rain that fell during the prior day. Is this the case? I seem to have a -ve deficit at the moment - so I assume that simply means it rained more yesterday than was lost to evapotranspiration.

 

"Irrigation Requirement - amount of water to be applied based on the accumulation of previous day(s) water deficits."

So this is just a running total of deficits? I assume this is only calculated once each day - and ignores any rain that falls after the calculation - or any ET that happens during the day. Is this correct?

 

By example, today.

 

Irrigation Needs 2013/05/03 at 04:00:00 is 0.3625 inches

ET is 0.1006 inches/day.

Yesterdays deficit is -0.0443 inches

Rain today so far is 0 inches

 

Irrigation Needs 2013/05/03 at 18:00:00 is 0.3625 inches

ET is 0.1006 inches/day.

Yesterdays deficit is -0.0443 inches

Rain today so far is 0.16 inches

 

It rained 0.16 inches between 4am and 6pm today - but the 'irrigation requirement' still shows 0.3625 now at 7pm. Shouldn't it have gone down?

The ETo, Irrigation Required and, Water deficit numbers are calculated once after Midnight. Rain today is a live number from WB.

 

Water_Deficit = ETo - ((Rain_Today + Irrigation) * Absorption_Factor)

Irrigation_Required = Irrigation_Required + Water__Deficit (cannot be less than 0)

 

Note that the Absorption_Factor is applied to both rainfall and irrigation.

 

I'm getting myself a little confused in that if it rains during the day (after the ET is calculated) but my cycle is triggered at 6pm - I seem to get a situation where the rain during the day is not assessed in determining if the 'Irrigation Requirement' threshold has been exceeded. Should I subtract 'Rain Today' from 'Irrigation Requirement' and see if that exceeds the threshold for irrigation at the end of the day?

 

What is everyone else doing?

 

Thanks,

 

Michael.

 

Add Rain_Today to the qualifiers in your irrigation program:

 

If Irrigation_Required > 0.5

and Rain_today < xx

 

Then

Run Irrigation_Program

[MWareman]

Awesome! - Thanks.

 

One small clarification...

 

 

Add Rain_Today to the qualifiers in your irrigation program:

 

If Irrigation_Required > 0.5

and Rain_today < xx

 

Then

Run Irrigation_Program

 

In the example...

 

If Irrigation_Required > 0.5

and Rain_today < 0.5

..this gets messed up if it effectively rained 0.4" (meaning I'm applying 0.4" too much - and wasting water).

 

If Irrigation_Required > 0.5

and Rain_today < 0.2

..this gets messed up if it effectively rained 0.3" (meaning I'm getting .2" too little).

 

Because Irrigation_Required is updated only once a day at midnight - what I really need to do is subtract Rain_Today from Irrigation_Required and see if the result of that exceeds my threshold. I cannot seem to do that in an ISY program (in the same way that water applied by irrigation is currently subtracted from the irrigation required when a cycle complete is executed).

 

I also have every-other-day and time-of-day restrictions to my irrigation - so I have to be able to do the math for twice a day irrigation on the days allowed. During the summer months (and factoring the absorption rate) it is very difficult to apply the needed water in only one cycle without busting the time restriction.

 

I can irrigate at 4am first - so the time from calculation (midnight) to 4 am is not so great. But the second cycle cannot be until 6pm - and there can be a substantial change between midnight and 6pm.

 

Functionally - is it possible that the Irrigation_Required calculation can be run on demand (rather than just at midnight) - and still function (rather than just at midnight)? Or - have a second program variable 'Irrigation_Required_Live' or similar tracking rain and ET 'real time' as it were. That way - I can have the ISY account for all the variables just before deciding if the threshold is exceeded?

 

I do also want to avoid the "Hey - look at that idiot - it's raining and his irrigation is running" comments.. - but I know that's simply a timer attached to the Rain_Rate.

 

Otherwise - I'm wondering if anyone else has solved the problem or rain falling after the Irrigation_Requirement was calculated - and how.

 

Thanks,

 

Michael.

[IndyMike]

Hello MWareman,

 

We're getting into "irrigation methods" here. This is very dependent on your location, soil structure, (and in your case) watering restrictions. I can offer some suggestions, but you'll really need to test to see what works best in your particular situation.

 

Awesome! - Thanks.

 

One small clarification...

 

 

Add Rain_Today to the qualifiers in your irrigation program:

 

If Irrigation_Required > 0.5

and Rain_today < xx

 

Then

Run Irrigation_Program

 

In the example...

 

If Irrigation_Required > 0.5

and Rain_today < 0.5

..this gets messed up if it effectively rained 0.4" (meaning I'm applying 0.4" too much - and wasting water).

 

If Irrigation_Required > 0.5

and Rain_today < 0.2

..this gets messed up if it effectively rained 0.3" (meaning I'm getting .2" too little).

 

Because Irrigation_Required is updated only once a day at midnight - what I really need to do is subtract Rain_Today from Irrigation_Required and see if the result of that exceeds my threshold. I cannot seem to do that in an ISY program (in the same way that water applied by irrigation is currently subtracted from the irrigation required when a cycle complete is executed).

 

I also have every-other-day and time-of-day restrictions to my irrigation - so I have to be able to do the math for twice a day irrigation on the days allowed. During the summer months (and factoring the absorption rate) it is very difficult to apply the needed water in only one cycle without busting the time restriction.

 

In the examples that you provided above, I would err on the side of applying too little water (example 2). Grass is pretty tolerant too little water. You can absolutely kill it with too much water (fungus and other diseases).

 

You need to envision your soil as a leaky container (sponge). It you overfill the container you will get runoff and rapid percolation. The soil will rapidly loose water until it achieves it's "Field Capacity". The Field Capacity is determined by the soil type and root dept of your grass. The heavier the soil and deeper the root depth, the more capacity you have.

 

I happen to have loamy sand with a ~8 inch root depth. From the table below:

1) Field capacity = (0.07 inches water/Inch depth) * (8 inch root depth) = 0.56" water

2) Allowable depletion (60%) = (0.6) * (0.56" Field Capacity) = 0.336

 

When the ISY tells me that the Irrigation Required = 0, it is effectively saying that the soil is at Field Capacity.

When it tells me that Irrigation Required = 0.336, I am at the maximum allowable depletion. I apply 0.2" water.

 

Because my soil is light and can't hold much water, I normally need to water daily in the Summer (4:00 AM). I also practice "deficit" irrigation - I allow my water balance to get below 60%. It promotes root growth in the grass.

 

Please perform the calculations for Field Capacity and post back. I have a suspicion that you are trying to apply too much water - don't overfill the container. Under-filling by 0.2 inches isn't a problem.

 

 

 

I can irrigate at 4am first - so the time from calculation (midnight) to 4 am is not so great. But the second cycle cannot be until 6pm - and there can be a substantial change between midnight and 6pm.

 

Functionally - is it possible that the Irrigation_Required calculation can be run on demand (rather than just at midnight) - and still function (rather than just at midnight)? Or - have a second program variable 'Irrigation_Required_Live' or similar tracking rain and ET 'real time' as it were. That way - I can have the ISY account for all the variables just before deciding if the threshold is exceeded?

 

I do also want to avoid the "Hey - look at that idiot - it's raining and his irrigation is running" comments.. - but I know that's simply a timer attached to the Rain_Rate.

 

Otherwise - I'm wondering if anyone else has solved the problem or rain falling after the Irrigation_Requirement was calculated - and how.

 

Thanks,

Michael.

 

Real time calculation of ET requires a real time measurement of Solar Radiation (Rs). Weather bug does not provide Rs and hence only daily calculations can be performed.

 

Real time updates of Irrigation_Required is left for the user to implement through programs as discussed above. While the ISY could perform this calculation - it would invalidate existing users programs. In other words, this is a question for the UDI team and the forum as a whole.

 

Your watering restrictions do present some unique challenges. I haven't had to deal with them. Please post back the following:

1) Soil type

2) Root Depth

3) Soil Absorption %

4) Current daily ET (estimate)

 

We'll see if there may be an inventive solution. Right now I'm thinking you could use State Variables to guestimate tomorrows ET loss (non-watering day) based on the time of year.

 

 

IM

[jmed999]

 

I happen to have loamy sand with a ~8 inch root depth. From the table below:

1) Field capacity = (0.07 inches water/Inch depth) * (8 inch root depth) = 0.56" water

2) Allowable depletion (60%) = (0.6) * (0.56" Field Capacity) = 0.336

 

When the ISY tells me that the Irrigation Required = 0, it is effectively saying that the soil is at Field Capacity.

When it tells me that Irrigation Required = 0.336, I am at the maximum allowable depletion. I apply 0.2" water.

 

 

-When you say you apply 0.2" of water do you mean your irrigation system applies 0.336" which equates to 0.2"? So you apply 0.336 and only 0.2" is absorbed, right? Seems like if you need 0.336" and allowable depletion = absorption factor you would need to apply 0.56" since 0.56*.6=0.336. If you want to replenish the amount that has depleted (0.336") then wont you need to apply 0.56" since only 0.336" will be absorbed?

 

-Also, for loamy sand (your soil) the ISY has an allowable depletion of 83% which is different from your chart of 60%. Why such a difference?

[IndyMike]

 

I happen to have loamy sand with a ~8 inch root depth. From the table below:

1) Field capacity = (0.07 inches water/Inch depth) * (8 inch root depth) = 0.56" water

2) Allowable depletion (60%) = (0.6) * (0.56" Field Capacity) = 0.336

 

When the ISY tells me that the Irrigation Required = 0, it is effectively saying that the soil is at Field Capacity.

When it tells me that Irrigation Required = 0.336, I am at the maximum allowable depletion. I apply 0.2" water.

 

 

-When you say you apply 0.2" of water do you mean your irrigation system applies 0.336" which equates to 0.2"? So you apply 0.336 and only 0.2" is absorbed, right? Seems like if you need 0.336" and allowable depletion = absorption factor you would need to apply 0.56" since 0.56*.6=0.336. If you want to replenish the amount that has depleted (0.336") then wont you need to apply 0.56" since only 0.336" will be absorbed?

 

-Also, for loamy sand (your soil) the ISY has an allowable depletion of 83% which is different from your chart of 60%. Why such a difference?

 

Hello jmed999,

 

I'm running with a Soil Absorption setting of 80%. I tell the ISY that I've applied .25" and it deducts 0.2" (80% * .25 inches) from the irrigation required.

 

On the subject of Soil Absorption - I regard this as a misnomer. In order to calculate soil absorption you need to know the Rain/Irrigation rate (inches/hour). That information isn't available to the ISY.

 

As an example: Heavy clay soil is capable of absorbing around 0.1" of water/hour.

1) If you are on a slope, and received 1" of rain in an hour, only 0.1" will be absorbed. The rest would be lost to runoff.

2) Given the same slope, if you received 1" of rain over the entire day (1/24 = 0.042 inches/hour). Most of the 1" of rain would be absorbed (until you saturate the clay).

 

Instead of using the term "Soil Absorption", I treat this as a "watering efficiency" and set it to 80%:

1) The 80% number is generally accepted as a rainfall efficiency in the irrigation industry. It accounts for runoff and evaporation from the plant canopy (water not reaching the soil).

2) The same 80% is applied to irrigation. An 80% efficiency is at the high end for most irrigation systems, particularly rotor systems that are operated during the day (spray evaporation, wind effects, poor overlap). You can compensate for this by simply running your system longer and telling the ISY that you are applying the same amount of water.

 

Summarizing the above:

1) I would suggest that everyone use a baseline of 80% absorption. People on slopes may need to "tailor" the number downward. People in flat areas may need to "tailor" upward.

2) Please do not use the "allowable depletion" from the ISY. Use the water balance table the I presented previously. The allowable depletion item was based on the "soil absorption" entry - as explained above, this can't be determine with the information the ISY has available.

3) There is no substitute for "measuring" your irrigation rate and coverage (overlap). This is particularly important for Rotor or impulse style heads. Most systems are installed with one size nozzle in all of the heads - this disregards the area covered (45, 180, 360 degrees) and leads to huge differences in the application rate.

 

Section 4 (page 19) of the following provides worksheets and describes how to perform a "catch can test" to determine your irrigation efficiency: http://www.irrisoft.net/downloads/manuals/InSite%20Users%20Guide.pdf

[jmed999]

-So everyone should use a absorption factor of 80% regardless of the type of soil you have?

 

-How can we not use the "allowable depletion"? It is calculation automatically and not really a way to turn it off.

 

-I'm actually doing the catch can method today using http://www.nrgideas.com/rg-107s

 

Thanks for your help!

[MWareman]

Thanks IndyMike - I have seen your other posts on the subject (especially the monster thread during development) and you are *way* more knowledgeable than I am on this subject. IT does seem though that the final algorithm and recomended programs are somewhat missing from the wiki. Especially the v3 program example linked from http://wiki.universal-devices.com/index.php?title=ISY-99i/ISY-26_INSTEON:How-To_Guide#Irrigation.

 

Ultimately - I'm only trying to ballpark it, and save water as much as possible. I don't have my system installed yet (next few weeks - depending on city permitting) - but I did get the EZFlora and am trying to figure the programming before I get the rest of the system in.

 

I plan on measuring the run time of each zone to get 0.5" of water deposited, on average. That will set the timings for me. Right now, I have completely bogus run times of 2 minutes a zone, for my (literally) 'dry' runs. I'm told I can easily get my 4 zones to put 0.5" down within an hour.

 

I'm not a gardener - I have no idea how to tell what kind of soil I have. This site http://casoilresource.lawr.ucdavis.edu/soilweb_gmap/ claims I have 325B 'Dresden silt loam, 2 to 4 percent slopes'. How that correlates to 'Soil Type' and '% Absorption' that you need, I don't know. For the time being, I have set the ISY 'Absorption Factor / Soil Type' to '58% - Loam'.

 

Daily ET as calculated by the ISY seems to vary - this is spring in the Chicago area. Seems to be between 0.8 and 1.7.

 

Root depth is something tricky - the area I will be irrigating is getting new sod (it's pretty dead after last years very dry summer - this is the main driving force of the project). So - I assume we start with just a couple of inches and adjust up as the turf grows in.

 

Honestly - I was hoping not to have to get into the science of it too much. I'm actually relatively OK with the irrigation requirement figures coming out of the ISY calculation so far. The issue I have (and am trying to solve) is the 'Irrigation Requirement' (as calculated at midnight) is currently decremented after a 'Irrigation Complete' command - but not with rain fall (until the next calculation run the following night). Without this - I may have an 'Irrigation_Requirement' or 0.6" at midnight - but if at 3am a storm blew thru and dropped 0.5" of rain, the irrigation would still cycle at 4am and be a complete waste. The limitations on programming prevent me from taking the 'Irrigation Requirement' value and subtracting the 'Rain_Today' variable and using that in the calculation.

 

Right now - I'm using programs to track if it's raining - and update a variable if it's 'recently rained'. If so - I simply skip the cycle. Likewise - I'm using calendar functions (from http://wiki.universal-devices.com/index.php?title=ISY-99i_Generic_Calendar_Using_Programs_and_Variables) to track odd or even days - and if even I suppress the cycle.

 

I then put several cycles within the allowed time. By local ordinance I can irrigate only on odd days 4am=>9am and 6pm=>9pm.

 

So, at 4am if the irrigation requirement is <0.5 - I skip it. If not, I initiate a 0.5" cycle and run 'Irrigation Complete' (reducing the irrigation requirement by 0.5).

At 5:30am, if the irrigation requirement is <0.5 - I skip it. If not, I initiate a 0.5" cycle and run 'Irrigation Complete' (reducing the irrigation requirement by 0.5).

At 7am, if the irrigation requirement is <0.5 - I skip it. If not, I initiate a 0.5" cycle and run 'Irrigation Complete' (reducing the irrigation requirement by 0.5).

At 6pm, if the irrigation requirement is <0.5 - I skip it. If not, I initiate a 0.5" cycle and run 'Irrigation Complete' (reducing the irrigation requirement by 0.5).

 

In all cases - if it rained in the 4 hours prior to a cycle - it's skipped. The theory being 'catchup' cycles will happen on the next odd day. Overall effect should be (I hope) an under irrigation. I do agree that over watering will lead to fungus problems - as well as just be wasting water.

 

However, I would prefer the rain block to be smarter then the current 'If it rained any amount int he last 4 hours - don't irrigate now' I have. If it's only rained 0.1" that should not stop a cycle being triggered if the 'Irrigation Requirement' from the last calculation is more than 0.6". Likewise - 'Rain_Today' of 0.2" should not stop the first cycle if the 'Irrigation Requirement' is > 0.7". This would then allow for a cycle still running if a recent rain was only very light - but still suppress it if the rain was heavier and extended. Basically - I want to irrigate less if it rains - but not block it entirely if the rain quantity is too light.

 

I sense I am going to have to call the ISY API from an external machine to get the 'Rain_Today' and 'Irrigation_Requirement', subtract one from the other and write the value back to the ISY as a variable - then trigger the cycle from the variable instead. I just surprise I cannot do this from a program on the ISY itself.

[MWareman]

In order to calculate soil absorption you need to know the Rain/Irrigation rate (inches/hour). That information isn't available to the ISY.

 

During a rain event - my ISY shows the rate in Rain_Rate coming from Weatherbug - and manual measurements I am planning to do will give me the inches/hour of my system. Does the ISY not take this into account at all? I would think that it could.

 

Anyway - I'm really not needing/wanting to get into this. Just adjusting the amount applied responding to the climate (ET and rain).

 

Michael.

[IndyMike]

Hi jmed999,

 

Answers below -

-So everyone should use a absorption factor of 80% regardless of the type of soil you have?

That would be my recommendation. As I stated, you may need to adjust depending on whether you have flat/sloped ground. The irrigation rate is your responsibility. If you have a high irrigation rate (inches/hour) and heavy soil/slopes you will need to apply multiple waterings to prevent runoff.

-How can we not use the "allowable depletion"? It is calculation automatically and not really a way to turn it off.

To the best of my knowledge, the "allowable depletion" is presented as a guide. It is not used for programming. I've actually requested that UDI eliminate this in favor of the water balance table above.

-I'm actually doing the catch can method today using http://www.nrgideas.com/rg-107s

 

Glad to hear that. I'd be interested in your system type (spray, rotor, rotator) and your results.

 

IM

[IndyMike]

Hello Michael,

 

I'm going to apologize up front because I will be ignoring many of your questions - let's cut to the chase:

 

• [*:20ddw585]You are installing a new irrigation system and new sod - both are sizable investments. New sod is a great way of obtaining an instant lawn. It's also a water PIG. Personally, I would talk to your sod installers about the irrigation requirements and do EXACTLY what they say. They should understand your local restrictions and the sod requirements. I'm guessing that the watering requirements will be far in excess of anything the ET calculations indicate. Get the SOD to establish itself first, then we can worry about efficiency.
  [*:20ddw585]Talk with your irrigation installers - you want all of your sprinkler heads "tuned" so the provide a constant rate across the zone (xx inches/hour).
  [*:20ddw585]After the system is installed, measure the application rate and coverage efficiency using the link I posted to Jmed999. Since you have a new system, I would call the installers if the irrigation rate changes significantly across a given zone (poor overlap/incorrect nozzle sizing).
  [*:20ddw585]Lastly - the ET numbers that you posted (0.8 and 1.7) are way off for Chicago (actually, there way off for most anywhere). If the units are in inches, you should be seeing around 0.14 inches/day. If the units are millimeters, you should be seeing around 3.56 mm/day.
  

 

Sorry for ignoring your questions on programming. I would much rather see you get the sod established first, and then worry about efficient watering.

 

IM

 

Thanks IndyMike - I have seen your other posts on the subject (especially the monster thread during development) and you are *way* more knowledgeable than I am on this subject. IT does seem though that the final algorithm and recomended programs are somewhat missing from the wiki. Especially the v3 program example linked from http://wiki.universal-devices.com/index.php?title=ISY-99i/ISY-26_INSTEON:How-To_Guide#Irrigation.

 

Ultimately - I'm only trying to ballpark it, and save water as much as possible. I don't have my system installed yet (next few weeks - depending on city permitting) - but I did get the EZFlora and am trying to figure the programming before I get the rest of the system in.

 

I plan on measuring the run time of each zone to get 0.5" of water deposited, on average. That will set the timings for me. Right now, I have completely bogus run times of 2 minutes a zone, for my (literally) 'dry' runs. I'm told I can easily get my 4 zones to put 0.5" down within an hour.

 

I'm not a gardener - I have no idea how to tell what kind of soil I have. This site http://casoilresource.lawr.ucdavis.edu/soilweb_gmap/ claims I have 325B 'Dresden silt loam, 2 to 4 percent slopes'. How that correlates to 'Soil Type' and '% Absorption' that you need, I don't know. For the time being, I have set the ISY 'Absorption Factor / Soil Type' to '58% - Loam'.

 

Daily ET as calculated by the ISY seems to vary - this is spring in the Chicago area. Seems to be between 0.8 and 1.7.

 

Root depth is something tricky - the area I will be irrigating is getting new sod (it's pretty dead after last years very dry summer - this is the main driving force of the project). So - I assume we start with just a couple of inches and adjust up as the turf grows in.

 

Honestly - I was hoping not to have to get into the science of it too much. I'm actually relatively OK with the irrigation requirement figures coming out of the ISY calculation so far. The issue I have (and am trying to solve) is the 'Irrigation Requirement' (as calculated at midnight) is currently decremented after a 'Irrigation Complete' command - but not with rain fall (until the next calculation run the following night). Without this - I may have an 'Irrigation_Requirement' or 0.6" at midnight - but if at 3am a storm blew thru and dropped 0.5" of rain, the irrigation would still cycle at 4am and be a complete waste. The limitations on programming prevent me from taking the 'Irrigation Requirement' value and subtracting the 'Rain_Today' variable and using that in the calculation.

 

Right now - I'm using programs to track if it's raining - and update a variable if it's 'recently rained'. If so - I simply skip the cycle. Likewise - I'm using calendar functions (from http://wiki.universal-devices.com/index.php?title=ISY-99i_Generic_Calendar_Using_Programs_and_Variables) to track odd or even days - and if even I suppress the cycle.

 

I then put several cycles within the allowed time. By local ordinance I can irrigate only on odd days 4am=>9am and 6pm=>9pm.

 

So, at 4am if the irrigation requirement is <0.5 - I skip it. If not, I initiate a 0.5" cycle and run 'Irrigation Complete' (reducing the irrigation requirement by 0.5).

At 5:30am, if the irrigation requirement is <0.5 - I skip it. If not, I initiate a 0.5" cycle and run 'Irrigation Complete' (reducing the irrigation requirement by 0.5).

At 7am, if the irrigation requirement is <0.5 - I skip it. If not, I initiate a 0.5" cycle and run 'Irrigation Complete' (reducing the irrigation requirement by 0.5).

At 6pm, if the irrigation requirement is <0.5 - I skip it. If not, I initiate a 0.5" cycle and run 'Irrigation Complete' (reducing the irrigation requirement by 0.5).

 

In all cases - if it rained in the 4 hours prior to a cycle - it's skipped. The theory being 'catchup' cycles will happen on the next odd day. Overall effect should be (I hope) an under irrigation. I do agree that over watering will lead to fungus problems - as well as just be wasting water.

 

However, I would prefer the rain block to be smarter then the current 'If it rained any amount int he last 4 hours - don't irrigate now' I have. If it's only rained 0.1" that should not stop a cycle being triggered if the 'Irrigation Requirement' from the last calculation is more than 0.6". Likewise - 'Rain_Today' of 0.2" should not stop the first cycle if the 'Irrigation Requirement' is > 0.7". This would then allow for a cycle still running if a recent rain was only very light - but still suppress it if the rain was heavier and extended. Basically - I want to irrigate less if it rains - but not block it entirely if the rain quantity is too light.

 

I sense I am going to have to call the ISY API from an external machine to get the 'Rain_Today' and 'Irrigation_Requirement', subtract one from the other and write the value back to the ISY as a variable - then trigger the cycle from the variable instead. I just surprise I cannot do this from a program on the ISY itself.

[IndyMike]

In order to calculate soil absorption you need to know the Rain/Irrigation rate (inches/hour). That information isn't available to the ISY.

 

During a rain event - my ISY shows the rate in Rain_Rate coming from Weatherbug - and manual measurements I am planning to do will give me the inches/hour of my system. Does the ISY not take this into account at all? I would think that it could.

 

Anyway - I'm really not needing/wanting to get into this. Just adjusting the amount applied responding to the climate (ET and rain).

 

Michael.

 

Michael,

 

The manual measurements of your irrigation system are correct. You do want to control the irrigation rate to make sure you aren't getting runoff.

 

The "Rain Rate" provided by Weatherbug is a maximum that does not include a duration. When Weatherbug shows a maximum rate of XX inches/hour, the ISY cannot determine how long the event lasted (seconds, minutes, hours). As a result, the ISY can't determine how much water may be lost to runoff.

 

There are systems that can determine actual rain rates and durations - they use dedicated sensors and are not inexpensive.

[MWareman]

Hello Michael,

 

I'm going to apologize up front because I will be ignoring many of your questions - let's cut to the chase:

 

No need to apologize! Any question answered is hugely appreciated. Even none answered with an opinion posted is still helpful to complete understanding.. and not wasted.

 

• [*:1sy8aghe]You are installing a new irrigation system and new sod - both are sizable investments. New sod is a great way of obtaining an instant lawn. It's also a water PIG. Personally, I would talk to your sod installers about the irrigation requirements and do EXACTLY what they say. They should understand your local restrictions and the sod requirements. I'm guessing that the watering requirements will be far in excess of anything the ET calculations indicate. Get the SOD to establish itself first, then we can worry about efficiency.
  [*:1sy8aghe]Talk with your irrigation installers - you want all of your sprinkler heads "tuned" so the provide a constant rate across the zone (xx inches/hour).
  [*:1sy8aghe]After the system is installed, measure the application rate and coverage efficiency using the link I posted to Jmed999. Since you have a new system, I would call the installers if the irrigation rate changes significantly across a given zone (poor overlap/incorrect nozzle sizing).
  [*:1sy8aghe]Lastly - the ET numbers that you posted (0.8 and 1.7) are way off for Chicago (actually, there way off for most anywhere). If the units are in inches, you should be seeing around 0.14 inches/day. If the units are millimeters, you should be seeing around 3.56 mm/day.
  

 

Sorry for ignoring your questions on programming. I would much rather see you get the sod established first, and then worry about efficient watering.

 

IM

 

I will indeed override all algorithms for the initial 10 days - as that's what our local village allows. I will program the aggressive initial watering needed - and that also needs a permit from the village. Such a pain - but that's how it is.

 

I'm more interested in the ET figure. I apologize - I apparently mis-posted (or mis-read my excel sheet..). I'm getting between 0.08" and 0.18" ET per day according to the ISY. That seems to fit with what you expect for the area.

 

I'll take your recommendation and set the absorption to 80%. That should slightly under-water for me - and that would seem to be OK for turf grass. As I've said - I'm not after perfection - just trying to avoid dead grass (either by over or under watering) - and keep the water bill to something tolerable.

 

Thanks for the help - it's very much appreciated.

 

Michael.

 

(Still interested if anyone has solved the rain fall post-calculation issue.. )

[MWareman]

The "Rain Rate" provided by Weatherbug is a maximum that does not include a duration. When Weatherbug shows a maximum rate of XX inches/hour, the ISY cannot determine how long the event lasted (seconds, minutes, hours). As a result, the ISY can't determine how much water may be lost to runoff.

 

There are systems that can determine actual rain rates and durations - they use dedicated sensors and are not inexpensive.

 

Weatherbug gives a rain_rate and a rain_today figure. Surely, the rain_today could be monitored with each reading (or every few readings, depending on reading rate) - to determine an actual rate per interval - and therefore be able to determine runoff and quantity absorbed when knowing the absorption rate per interval?

 

Either way - this is more into it than I think I need. I just want to base my irrigation on last nights 'irrigation_required' less the 'rain_today' at the moment of deciding if we need to start a cycle. Should be easy - but I cannot seem to figure it out. And I do understand that I'm assuming 100% absorption of the rain here - but it's close enough for me. When the irrigation_needed figure is calculated again at the end of the day it will be brought back to the correct amount accounting for absorption.

 

Michael.

[jmed999]

I'm not a gardener - I have no idea how to tell what kind of soil I have. This site http://casoilresource.lawr.ucdavis.edu/soilweb_gmap/ claims I have 325B 'Dresden silt loam, 2 to 4 percent slopes'. How that correlates to 'Soil Type' and '% Absorption' that you need, I don't know. For the time being, I have set the ISY 'Absorption Factor / Soil Type' to '58% - Loam'.

 

Wareman, May I suggest using this technique to determine soil type? I used this method and was surprised! Hope this helps!

 

http://www.finegardening.com/how-to/articles/hows-your-soil-texture.aspx

[IndyMike]

Weatherbug gives a rain_rate and a rain_today figure. Surely, the rain_today could be monitored with each reading (or every few readings, depending on reading rate) - to determine an actual rate per interval - and therefore be able to determine runoff and quantity absorbed when knowing the absorption rate per interval?

 

Either way - this is more into it than I think I need. I just want to base my irrigation on last nights 'irrigation_required' less the 'rain_today' at the moment of deciding if we need to start a cycle. Should be easy - but I cannot seem to figure it out. And I do understand that I'm assuming 100% absorption of the rain here - but it's close enough for me. When the irrigation_needed figure is calculated again at the end of the day it will be brought back to the correct amount accounting for absorption.

 

Michael.

 

True, the ISY could calculate average rate if it had a reliable Weatherbug feed (xx readings per hour) to calculate an average. Many sites do not support multiple readings/hour and other factors such as user network issues and Weatherbug server loading make this a questionable calculation.

 

If a rain rate could be determined, we would then be faced with how to apply it. Level clay soil would generate standing water that would eventually be absorbed (80% absorption). Clay soil on a slope would generate runoff (10% absorption). In order to apply the information, we would need a multi-zone setup with information on the soil type(s) and slopes.

 

The above sounds as if I'm making excuses. I have put a fair amount of time into researching different ET system implementations. The commercial systems that try to achieve the level of precision required for rain rate/runoff calculations use dedicated sensors and muti-zone definitions. Neither are currently available to the ISY.

 

Stepping down from the podium...

 

From your example program below - Your ET will not change significantly in the morning hours due to high humidity and no sun. Rather than checking to the 0.5 limit, why not check a range of depletion and simply run at 4am:

 

If irrigation requirement > 0.4 (run) This will help cover your 0.15 ET for the day.

 

For the rain instances, you can use a series of programs to program a state variable:

 

State 0 (rain 0 to .1)

if Rain_today> 0

and Raid_today <=0.1

Then Rain_state = 0

 

State 1 (rain .1 to .2)

if Rain_today > 0.1

and Rain_today <=.2

Then Rain_state = 1

 

Irrigation

if irrigation requirement > 0.4

and Rain_State = 0

Then

Run irrigation

 

So, at 4am if the irrigation requirement is <0.5 - I skip it. If not, I initiate a 0.5" cycle and run 'Irrigation Complete' (reducing the irrigation requirement by 0.5).

At 5:30am, if the irrigation requirement is <0.5 - I skip it. If not, I initiate a 0.5" cycle and run 'Irrigation Complete' (reducing the irrigation requirement by 0.5).

At 7am, if the irrigation requirement is <0.5 - I skip it. If not, I initiate a 0.5" cycle and run 'Irrigation Complete' (reducing the irrigation requirement by 0.5).

At 6pm, if the irrigation requirement is <0.5 - I skip it. If not, I initiate a 0.5" cycle and run 'Irrigation Complete' (reducing the irrigation requirement by 0.5).

 

Other comments -

1) Your silt loam is actually a much nicer soil than what I have. Use the charts above to gauge your watering needs (after the sod is established).

2) After the initial 10 days your sod will still have next to no roots (maybe 2"). I have no personal experience with sod. I would listen to your sod installers on how much water/how often to apply. You are installing at a really tough time of year. The 0.5" in your program examples should be excessive given the short roots (but listen to your sod people).

3) I am not a fan of watering in the evening in our areas (I'm 90 miles east of you). Prolonged wet periods in the summer promote nasty diseases. I would rather underwater than water after 6 PM.

4) The chart below shows the monthly average ETo for your area. This includes rainfall/cloudy cool days. Some hot summer days may be significantly higher (2x). Even so, you should not have a problem with odd/even watering once your sod is established.

[JMC]

Sorry for reopening an old thread but this subject seems to be the natural place for my question.

 

I'm running 4.05 on ISY 994i pro, Windows 8. It's been working fine but I've recently noticed that Weatherbug is resetting Rain Today to 0 around 10pm. At first I thought it might be my particular station (KAUN) but this morning I switched it to KLHM and it did the exact same thing. Yesterday KAUN showed an accumulation of around 0.4" of rain during the day but when I checked after 10pm (I have my ISY as one of my home pages on Firefox) the Rain Today was 0. This morning I switched my site to KLHM and it showed an accumulation of 0.02" through the day but when I checked at 10pm Rain Today was 0.

 

I have no idea if the problem is with WeatherBug or with 4.05 since we are only now ending an extended period with no rainfall and 4.05 never had a chance to adjust Irrigation Requirement for rain until this week.

 

mike

[MWareman]

My first thought is to check that you have the timezone of the ISY set correctly. For instance, if it is set to Pacific time and you are in the Midwest, I would expect the variables to reset at 10pm local time.

 

Second thing to check is any programs that issue an 'Irrigation Reset' command. That command will also reset the numbers.

 

Michael.

[IndyMike]

Hello Mike,

 

Good catch. I just checked my ISY logs and my Rain_today value appears to be setting around 11:00 PM. This appears to have kicked in after the time change on Nov 3.

 

Odd thing is -

1) You didn't change times in AZ.

2) I believe the ISY reports the Rain_today value directly as reported by Weatherbug.

 

This may be a Weatherbug issue. If you are getting rain, and have the opportunity, could you check the actual Weatherbug site to see what it is reporting after 10 PM?

[JMC]

Timezone is correct. I will definitely monitor the next rain, which is forecast for next Wednesday.

 

One thing I did not mention is that when the Rain Today reset to 0 neither Yesterday's Water Deficit nor Irrigation Requirement reflected the change. They remained the same as they had been when Rain Today had a positive value and the following morning their values were the same as I would have expected with zero rainfall.

 

mike

[IndyMike]

Hi Mike,

 

My logs are showing that as well:

1) 10:00 PM 0.5" rain.

2) 11:00 PM 0 rain.

3) 12:01 PM Irrigation required calculated for 0 rainfall.

 

Still not sure whether this is the ISY or Weatherbug.

[TJF1960]

Not to hijack this thread or turn attention away from jmc but I am thinking WB may be having problems or have made some changes. For the last month maybe a little more my sprinklers have not been turning on. ISY Et shows 0.016" for yesterday which is about what it has been running for the last month. At this rate my sprinklers wont fire until xmas. I was on station KBAB but a couple of days ago changed to the same one jmc switched to (KLHM) and the et has been showing about the same. Not sure where to go from here.

 

My settings are:

P-M, Interior plains, 70% - Slope, .7, water applied .386"

 

Et seemed fine all summer and I was on 4.0.5 from its release until 4.1.0 was released.

 

If there is anything I can do just let me know.

 

Thanks,

Tim

[IndyMike]

Not to hijack this thread or turn attention away from jmc but I am thinking WB may be having problems or have made some changes. For the last month maybe a little more my sprinklers have not been turning on. ISY Et shows 0.016" for yesterday which is about what it has been running for the last month. At this rate my sprinklers wont fire until xmas. I was on station KBAB but a couple of days ago changed to the same one jmc switched to (KLHM) and the et has been showing about the same. Not sure where to go from here.

 

My settings are:

P-M, Interior plains, 70% - Slope, .7, water applied .386"

 

Et seemed fine all summer and I was on 4.0.5 from its release until 4.1.0 was released.

 

If there is anything I can do just let me know.

 

Thanks,

Tim

 

Tim,

 

The data below was pulled from WeatherUnderground. It shows what I believe the ISY should be calculating for the Month of November. The ISY should display one of the ETc values depending on which Kc you have selected.

 

I have no way of telling whether the Weathbug feed from KBAB is operating properly. All I can say is that the WeatherUnderground data looks OK.

 

[TJF1960]

I stand corrected, thanks IndyMike. Those figures jive with what I have been seeing. Last winter my sprinklers were run about every 4 days to a week depending on weather. But now thinking about it you and UDI had made some positive changes to the calculations as I recall, and it appears they are dead on now.

 

Thank you!

 

Tim

[IndyMike]

Tim,

 

Thank you for confirming the calculations. I was sweating that one a bit...