How does water reach a drainage basin

Water reaches a drainage basin mostly through or by precipitation. A drainage basin is an area of land that is drained by a river and together with its tributaries. The boundary of a drainage basin is known as the watershed and is a ridge of a high lying land beyond which precipitation may drain into other neighboring basins. Precipitation forms the major source of water that comes into the basin. It may be in form of light or heavy rain and amounts vary over time and space. Usually, thunderstorms are short heavy and may be confined to small areas.