My ET seems to be to high

[jmed999]

My evapotranspiration is running about 0.12" per day. So at 0.25 intervals my system is watering real often for recent weather conditions. I watered way less than this last year. I'm not looking forward to my water bill, lol!

 

How can I check the accuracy of the ET for my location?

 

Thanks guys!

[IndyMike]

Jmed999,

 

A little criticism - all that I can tell from your post is

 

YOU DON"T LIVE NEXT DOOR TO ME! My ET is running 0.07 for the past few days (overcast).

 

I'm more than willing to help, but you have to toss me a bone.

 

1) location

2) Crop coefficient (Kc setting)

3) Calculation method (P-M or S-H)

 

Feel free to PM me if you don't wish to post on the forum.

[jmed999]

Jmed999,

 

A little criticism - all that I can tell from your post is

 

YOU DON"T LIVE NEXT DOOR TO ME! My ET is running 0.07 for the past few days (overcast).

 

I'm more than willing to help, but you have to toss me a bone.

 

1) location

2) Crop coefficient (Kc setting)

3) Calculation method (P-M or S-H)

 

Feel free to PM me if you don't wish to post on the forum.

 

No worries. By "How can I check the accuracy of the ET for my location?" I was asking what I need to provide to do this. I knew location but wasn't sure what else. I should have worded it differently. I'll PM you so I don't have to give location here. Thanks!

[IndyMike]

Jmed,

 

I downloaded data from one of your local WeatherUnderground sites for the past month (below). I ran the P-M calculation on this data and produced the values in the table below.

 

I used the following resource to look up predicted ETo for states in your area: http://www.nc-climate.ncsu.edu/ETdynamic2.php?date=2013-05-27&unit=inches. One of the locations listed is your regional airport. ETo values from that station appear to track the ISY calculation within 0.01".

 

Not sure what to tell you about last years values. Your current values are tracking the NCSU predictions for your location.

 

[jmed999]

Thanks for your time! I wonder what station you used? I don't think it was my personal station because my ET for the 27th was 0.1204. That is pretty close. So if I put down .25" of water I guess I'll be watering about every other day and it hasn't even got real hot yet. Sounds like I'll be watering almost daily when August gets here. Oh well it is what it is.

 

I have sandy loam soil. Maybe I should water more than .25". Also, how do I know if I live in a coastal region or interior plains?

 

Thanks again!

[IndyMike]

Thanks for your time! I wonder what station you used? I don't think it was my personal station because my ET for the 27th was 0.1204. That is pretty close. So if I put down .25" of water I guess I'll be watering about every other day and it hasn't even got real hot yet. Sounds like I'll be watering almost daily when August gets here. Oh well it is what it is.

 

I have sandy loam soil. Maybe I should water more than .25". Also, how do I know if I live in a coastal region or interior plains?

 

Thanks again!

 

jmed,

 

You should be using the "interior plains" setting for your area. This yields ETo values nearly identical to those predicted for your regional airport.

 

I downloaded data and CRONOS predictions for your Airport. The following is a comparison for the past month. The data is actually for 90 days, even though I'm only showing a month.

 

1) ETo comparison: The ISY and the NCSU CRONOS system agree within 0.0315" over 90 days. The equates to 0.00035" difference per day.

2) ETc comparison: The ISY is using a Kc of 0.6 for warm season grass. The NCSU CRONOS system is using a Kc of 0.8 for the same grass. I don't know why. All of the literature that I can find indicates that a Kc of 0.6 is correct for warm season grass.

 

[jmed999]

Thanks for your time IM!