Issue with SWAT+ Water Allocation Module Using Reservoir and Aquifer Irrigation

[poojitha kondeti]

Dear Sir/Madam,

I am currently facing an issue while running SWAT+ when implementing irrigation using the water allocation (WRO) module. I am attempting to simulate irrigation from two different sources: reservoirs and aquifers.

When both irrigation sources (reservoir and aquifer) are enabled simultaneously, SWAT+ crashes with the following error:

forrtl: severe (157): Program Exception - access violation

Image              PC                Routine            Line        Source
SWAT+.exe          00007FF6486909CF  WALLO_WITHDRAW             87  wallo_withdraw.f90
SWAT+.exe          00007FF64868E828  WALLO_CONTROL              81  wallo_control.f90
SWAT+.exe          00007FF64868A7D5  TIME_CONTROL              246  time_control.f90
SWAT+.exe          00007FF64853DBA7  MAIN                      129  main.f90
SWAT+.exe          00007FF6486AD6FB  Unknown               Unknown  Unknown
SWAT+.exe          00007FF6486B5C60  Unknown               Unknown  Unknown
KERNEL32.DLL       00007FF812F6E8D7  Unknown               Unknown  Unknown
ntdll.dll          00007FF81522C53C  Unknown               Unknown  Unknown

To isolate the issue, I tested two separate scenarios:

Case 1: Reservoir irrigation only (aquifer irrigation disabled)
The model runs successfully without any errors.

Case 2: Aquifer irrigation only (reservoir irrigation disabled)
The model crashes with a different error:

forrtl: error (72): floating overflow
Image              PC                Routine            Line        Source
SWAT+.exe          00007FF6EB1D87C5  AQU_1D_CONTROL            139  aqu_1d_control.f90
SWAT+.exe          00007FF6EB284B74  COMMAND                   280  command.f90
SWAT+.exe          00007FF6EB5DA830  TIME_CONTROL              254  time_control.f90
SWAT+.exe          00007FF6EB48DBA7  MAIN                      129  main.f90
SWAT+.exe          00007FF6EB5FD6FB  Unknown               Unknown  Unknown
SWAT+.exe          00007FF6EB605C60  Unknown               Unknown  Unknown
KERNEL32.DLL       00007FF812F6E8D7  Unknown               Unknown  Unknown
ntdll.dll          00007FF81522C53C  Unknown               Unknown  Unknown

[poojitha kondeti]

Based on these tests, it appears that:

1. Reservoir-based irrigation functions correctly on its own.

2. Aquifer-based irrigation leads to numerical instability (floating overflow).

3. Combining both sources results in an access violation during water withdrawal.

I would greatly appreciate your guidance on:

1. Proper configuration of combined reservoir and aquifer irrigation in the water allocation module.

2. Recommended parameter ranges or safeguards for aquifer-based irrigation to avoid numerical instability.

3. Any known limitations or best practices when using multiple irrigation sources together in SWAT+.

Thank you very much for your time and support. I look forward to your suggestions.

Kind regards,
Poojitha K.