4. Drainage

Rivers have always been of supreme importance to man, providing focal points for habitation, water for cultivation and avenues to travel, water power and recreation. A river or stream is a body of water flowing in a channel. The term ‘drainage’ describes the river system of an area. It is an integrated system of a river and its tributaries which collect and funnel surface water to the sea. The area drained by a single river system is called a drainage basin. The boundary line separating one drainage basin from the other is known as the watershed. A river drains the water collected from a specific area, which is called its ‘catchment area’. The catchments of large rivers are called river basins while those of small rivulets and rills are often referred to as watersheds. Watersheds are small in area while the basins cover larger areas.