Stream & Catchment Delineation Using QGIS (r.watershed)

In this tutorial, we explore how to delineate a catchment using QGIS, focusing on the powerful r.watershed algorithm from the GRASS GIS toolbox. This tool allows users to generate flow direction, flow accumulation, and watershed boundaries directly from a Digital Elevation Model (DEM). Whether you're a student learning hydrological analysis for the first time or a practitioner refining your workflow, this guide provides a clear, step‑by‑step approach to producing reliable catchment boundaries using open‑source software.