Watershed Delineation Techniques: Traditional Methods vs. Modern GIS-Based Approaches

Watershed delineation is a basic requirement in hydrological modeling, environmental planning, and water resource management. Historically, delineation was carried out manually with the aid of contour lines and topographic maps, a tedious and error-prone process. As Geographic Information System (GIS) technology improved and high-resolution Digital Elevation Models (DEMs) were made available, contemporary delineation methods have become quicker, more precise, and scalable. This review critically assesses the development from traditional to GIS-based watershed delineation methodologies. It enlists major methodologies, software tools used, required data, and algorithmic frameworks like D8 flow direction and accumulation models. Case studies and comparative analyses illustrate the superiority of contemporary techniques in terms of accuracy, efficiency, and reproducibility. Although flat terrain and data preprocessing pose some difficulties, GIS-based approaches are a major leap forward from conventional techniques and are crucial for future hydrological analysis advances.