gwflow observation wells not generating output (rev. 62) — missing gwflow.input, no observation-cell mechanism in Editor

[sharafat hussain]

Hi All I have the following issue 

SWAT+ Issue Report Template

1. Primary Issue Location

• Component: SWAT+ Editor / SWAT+ Executable / gwflow module (observation-well output specifically)
• Area of impact: Model input (no clear mechanism to define gwflow observation wells) and model output (gwflow_obs_day.txt / gwflow_obs_aa.txt remain empty — header only)

2. Software Versions

• GIS Interface: QGIS with QSWAT+
• SWAT+ Editor: v4.0.1–v4.0.2 (title bar shows 4.0.2; codes.gw file header shows "written by SWAT+ editor v4.0.1")
• SWAT+ Revision: rev. 62

3. Project Characteristics

• Watershed Details: Yugu stream watershed, South Korea; paddy-dominant land use, ~29,734 ha; gwflow grid is structured, 100 m cell size, 252 rows × 203 columns, 30,341 active cells
• Modeling Aim: Streamflow and groundwater head calibration/validation, including paddy-to-paddy HRU cascade routing and groundwater-aquifer interaction via gwflow

4. Description of Issue

• The Problem: gwflow_obs_day.txt and gwflow_obs_aa.txt output files never populate with data (header rows only, e.g., "-99 = not simulated" placeholder), even after setting print.prt's gwflow_obs row to print daily/annual output. I cannot find a mechanism in SWAT+ Editor or QSWAT+ to define which grid cells should be treated as observation wells for head output. codes.gw has no observation-cell count/list section, and gwflow_cell_definition.txt has no observation flag column. There is no gwflow.input file present in TxtInOut.
• Steps to Reproduce: (1) Set print.prt's gwflow_obs row to y for daily output, re-run — no output. (2) Checked SWAT+ Editor → Connections → Groundwater Flow → Cells page for an observation flag column — none exists. (3) Edited a gwflow_obs_points.shp point shapefile (found in project folder) with target well coordinates, re-ran — no output. (4) Manually created a gwflow_obs_head text file listing cell IDs, re-ran — no output. I found a related thread (Bontha Sai Kiran, March 2026, "Follow-up on SWAT+ gwflow setup...") describing a working gwflow_obs_head mechanism enabled via a modified gwflow.input file and custom executable provided directly by the developer — is this the correct current path for rev.62, and if so, could I get the same file/executable, or documentation on the current standard method?

5. Supporting Data (Optional)

• Link to TxtInOut folder: https://drive.google.com/drive/folders/1XsdpzsncNUMx_b7AtjVONk_UVj9yELp3?usp=sharing