Possible SWAT+ Check issue with monthly recall point-source flow summary

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Namraj Jaishi

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May 8, 2026, 9:56:30 AM (11 days ago) May 8

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Hello SWAT+ Editor/SWAT+ team,

I am modeling the Caney Creek watershed in Montgomery County, Texas using SWAT+ rev. 61.0.2.61 and SWAT+ Editor v3.2.1. I added monthly recall point-source data using rec_typ = 2, with each pt###.rec file containing monthly flo values in m³, following the SWAT+ recall documentation.

I noticed a possible issue or confusing behavior in SWAT+ Check under the Point Sources section. SWAT+ Check reports:

Total Point Source + Inlet Load:

Flow = 8.54 cms
Sediment = 60,470 Mg/yr
Nitrogen = 824,017 kg/yr
Phosphorus = 865 kg/yr

Load from Inlet + PS:

Flow = 99.75%

However, when I directly audit the active monthly recall files listed in recall.rec, the point-source flow is much smaller:

Active sources:
pt017, pt026, pt032, pt043, pt055, pt077, pt087, pt097, pt103, pt107

Direct calculation from the active pt*.rec files:

Total flow over full simulation = 23,533,901.5 m³
Correct mean point-source flow = 0.02869 cms
Correct mean point-source flow = 0.6549 MGD
Correct maximum monthly point-source flow = 0.4324 cms
Correct maximum monthly point-source flow = 9.8701 MGD

The channel output also shows that streamflow is much larger than the point-source input. For example, in channel_sd_yr.txt, flo_out for the main channel is around 7–8 cms on average, so the point-source flow should not be close to 99.75% of total flow.

Interestingly, if I divide the total multi-year recall volume by about 32 days, I get almost the same value as SWAT+ Check:

23,533,901.5 m³ / (32 × 86,400 s) ≈ 8.51 cms

This is very close to the 8.54 cms shown in SWAT+ Check. It looks like SWAT+ Check may be converting the total simulation monthly recall volume using an incorrect or unintended time denominator, rather than calculating the average point-source discharge over the full simulation period.

Could you please clarify how SWAT+ Check calculates “Total Point Source + Inlet Load” for monthly recall objects? Is this expected behavior, or could it be a bug in the point-source flow summary for rec_typ = 2 monthly recall data?

For reference:

SWAT+ rev: 61.0.2.61
SWAT+ Editor: v3.2.1
Recall type: monthly, rec_typ = 2
flo units in pt*.rec: m³ per monthly timestep
Output folder: TxtInOut
Main files checked: recall.rec, pt*.rec, channel_sd_yr.txt, channel_sd_mon.txt