Dear All,

 I hope this message finds you well. Actually, I have a problem with the irrigation management in SWAT model and I would appreciate if you can consult me on this issue. In my SWAT model I defined the irrigation manually in mgt files using mgt_op=2 and introduced the values of IRR_AMT for each subbasin and HRU  and the source of the irrigation one by one based on available data. I have three kinds of irrigation sources which are applied in my model: reach or dam or shallow aquifer. For some subbasins and HRUs (for example hru 1 sub1 or hru6 sub1...) the irrigation is defined to be from the reservoir dam but as I checked the OUTPUT.HRU of the SWAT in these regions some parts of irrigation (varied 20% to 80% for some HRUs) are supplied from the shallow aquifer which the value of SA_IRR (irrigated water from the shallow aquifer) shows that in the output file. It is contradictory that in the theoretical manual is also said as follows: For a given irrigation event, SWAT determines the amount of water available in the source. The amount of water available is compared to the amount of water specified in the irrigation operation. If the amount available is less than the amount specified, SWAT will only apply the available water. (ver2009, p 375) Furthermore, I checked the model with different sources added on by one to debug the problem. If all the irrigation source of  a specific subbasin (all HRUs) assumed to be from reach, dam or unlimited source then the  SA_IRR (irrigated water from the shallow aquifer) will be zero but if the shallow aquifer introduced as irrigation source for one or more HRUs of a specific subbasin, the other HRUs can also extract the rest of their irrigation water demand from the shallow aquifer as the SA_IRR will be nonzero. It happened for all the other conditions (IRR_SC=1 or RR_SC=2 or 5  According to the analysis of the irrigation source in my SWAT project, I got the following conclusion: If you define shallow aquifer as an irrigation source in one or some of the HRUs of a specific subbasin, then in all of the HRUs of that subbasin, the SWAT model first supplies the water from the defined source (dam or reach) and then it tries to supply the rest from the shallow aquifer. So I would appreciate if you let me know why the rest of the irrigation demands supplied from the shallow aquifer, whereas the reservoir is defined as source location of the irrigation. The output.hru file for one year of running is attached. Please let me know if you need any further information. Thank you for your kind support in advance. Best Regards,