What is a catchment area or watershed?

A catchment area (watershed or drainage basin) is the land area that drains water to a common outlet point like a river, lake, or ocean. It is delineated by topographic divides or ridgelines where water flows in opposite directions. Catchment area directly affects runoff volume - larger catchments produce more runoff for the same rainfall. Understanding catchment boundaries is essential for water resource planning, flood estimation, and environmental assessment.