Catchment Area of a River:
The catchment area of a river is the geographical area from which water drains into a particular river system. It is also known as a river basin, catchment basin, or drainage area. This area is defined by the topography of the land, where all the precipitation, such as rainfall or snowmelt, within the boundaries of the catchment area flows into the river.

Drainage Basin:
A drainage basin is the total area drained by a river and its tributaries. It encompasses all the land, hills, and valleys where water flows into a specific river system. It is a larger concept that includes the catchment area of the main river and all its tributaries. The drainage basin is separated from other basins by high points called water divides.

Watershed:
A watershed is often used interchangeably with the term drainage basin, but it can have a slightly different meaning. A watershed refers to the land area where all the water, sediments, and dissolved substances flow into a common outlet, such as a lake, river, or ocean. It can include multiple drainage basins within its boundaries.

Difference between Watershed and Water Divide:
The terms watershed and water divide are related but have distinct meanings:

1. Watershed: A watershed refers to the entire land area where water drains into a common outlet. It includes all the areas that contribute to the flow of water, including the main river and its tributaries. Watersheds are often delineated based on the topography and hydrological patterns of the land.

2. Water Divide: A water divide, also known as a watershed divide or drainage divide, is a ridge or high point of land that separates one watershed from another. It is the boundary that determines which way water will flow. When precipitation falls on opposite sides of a water divide, it will flow in different directions, ultimately draining into different river systems.

In summary, while a watershed refers to the entire land area draining into a common outlet, a water divide defines the boundary between different watersheds by separating the flow of water. The water divide determines which watershed a particular area belongs to, while the watershed encompasses all the land that contributes water to a specific outlet.