Managing missing MUKEYs in the QSWAT+ SSURGO database

The Soil and Water Assessment Tool Plus (SWAT+) is a widely used hydrological model for simulating water flow, sediment transport, and the impacts of land management on watersheds. It relies on soil data to represent how soil properties influence water movement, nutrient cycling, and crop growth within a watershed. The Soil Survey Geographic (SSURGO) database provides detailed, high-resolution soil information essential for such modeling. However, a common challenge arises when missing (Map Unit Keys) in the SWAT+ SSURGO database prevents the creation of Hydrological Response Units (HRUs), effectively halting model development. This study presents a method using QGIS to resolve missing MUKEY issues. Specifically, we demonstrate the use of QGIS's Eliminate Selected Polygons tool with the "Largest Common Boundary" option to merge missing MUKEY polygons, maintaining spatial coherence and enabling HRU generation. This approach simplifies the workflow, reduces manual effort, and improves model readiness and accuracy.•The study presents a method for resolving missing MUKEYs in the QSWAT+ SSURGO database, facilitating further development of SWAT+ and minimizing manual errors.•QSWAT+ version 3.0.2 improves error reporting by listing missing MUKEYs in the QGIS log, simplifying troubleshooting.•Using QGIS's Eliminate Selected Polygons tool with the "Largest Common Boundary" option preserves spatial integrity while addressing missing data gaps.