The area from which a river collects rainwater and drains it into its channel is called its:

The catchment area of a river is the total area of land from which rainwater, snowmelt and groundwater flow into the river and its tributaries. All the water falling in this area "is caught" and drained by the river.

Related terms:

• Drainage basin or river basin: the area drained by a river and all its tributaries; it is broadly the same as the catchment.
• Watershed or water divide: the high ground that separates one catchment (basin) from another.
• The catchment of a dam or reservoir is the area upstream of the dam that supplies water to it.

Importance of catchment areas:

• The size, slope, soil, vegetation and rainfall of a catchment determine how much water flows in the river and how quickly.
• Forests and vegetation in the catchment slow down runoff, reduce soil erosion and help recharge groundwater.
• Deforestation, mining and construction in the catchment increase floods and silt in rivers and reservoirs.

Catchment area treatment:

• Projects such as afforestation, check dams, bunds and terracing are carried out in catchments to reduce silt entering reservoirs and to conserve soil and water.
• This is called catchment area treatment and is a part of watershed management.

Large catchments in India:

• The Ganga basin is the largest river basin in India, covering about a quarter of the country.
• The Godavari has the largest basin among peninsular rivers.

Catchment and flooding:

• When heavy rain falls over a large part of a catchment at the same time, the river may flood downstream.
• Urban areas with many paved surfaces send water quickly into drains and rivers, increasing urban flooding.

Why not the other options?

• ✗A delta is the land built of sediment at a river's mouth.
• ✗A floodplain is the flat land next to a river that floods.
• ✗An estuary is the tidal mouth of a river.