SWAT+ GWFLOW: Groundwater recharge (rech) much lower than soil profile percolation

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veerendra gopi

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Jul 3, 2026, 9:57:44 AM (yesterday) Jul 3

to QSWAT+

Hello everyone,

I am currently working with a SWAT+ model coupled with GWFLOW and have encountered an issue regarding the groundwater water balance.

Software versions

SWAT+ Editor: 3.2.4
QSWAT+ Revision: 61.0.2

Project information

Watershed area: ~30,000 km²
HRU threshold: 10%
Objective: Water balance and surface water–groundwater interaction

Issue

The model runs successfully, but after enabling GWFLOW I observed that the annual groundwater balance output (gwflow_balance_gw_yearly.txt) reports groundwater recharge (rech) values that are substantially lower than the annual percolation leaving the soil profile reported in the SWAT+ water balance.

From my understanding, once GWFLOW is enabled, the percolation leaving the soil profile should largely become recharge to the groundwater model, except for any processes such as delays, storage, or other losses. However, the reported recharge is considerably smaller than the percolation values, resulting in a noticeable mismatch.

I would appreciate guidance on the following questions:

Should the annual groundwater recharge (rech) in GWFLOW approximately match the annual soil profile percolation?
Which processes within SWAT+ GWFLOW can cause recharge to be substantially lower than percolation?
Which input files or parameters should I examine to identify the source of this discrepancy?
Is there a recommended workflow to verify that recharge is being correctly transferred from SWAT+ HRUs to the GWFLOW grid cells?
Can this discrepancy be reduced through calibration? If so, which parameters are typically the most influential?

Link to project folder:
https://drive.google.com/file/d/1vqBXFfmqS6dn4DIm1OSq3kIQt1pDkGlB/view?usp=drive_link