What is a Catchment Area?

A Catchment Area (also called a drainage basin or watershed) is the entire geographical area of land from which all surface water (rainwater, melting snow, streams) flows downward and collects into a single main river, lake, or reservoir.

Imagine a giant bowl. Any rain that falls inside the bowl will eventually run down to the bottom. The inside of the bowl is the catchment area, and the bottom is the river or lake.

1. Water Supply: Cities depend on the catchment areas of dams and reservoirs for their drinking water. If it doesn't rain in the catchment area, the dam won't fill up.
2. Ecology: The health of a river depends entirely on the health of its catchment area. Deforestation in a catchment area leads to soil erosion and muddy rivers.
3. Flood Control: A well-vegetated catchment area absorbs rainwater slowly, preventing sudden flash floods downstream.

They are often used interchangeably. However, 'Drainage Basin' is usually used for large river systems (like the Ganga Basin), while 'Catchment Area' is often used for the specific area feeding a smaller river, lake, or a man-made dam.