The largest water basin in the world is the Amazon Basin. It spans 8 countries in South America. It is made up of two systems: a superficial (or fluvial) system – the Amazon River – and an underground one, the Hamza River, probably the longest underground river in the world.
In North America, the largest basin is the Mississippi Basin, which consists of the Mississippi and Missouri Rivers. It is the fourth-largest basin in the world. It covers more than three million square kilometers, its average flow rate is 18,000 cubic meters per second, and it crosses 10 of the 50 states in the United States.
The largest basin in Africa is that of the Congo River, covering almost 4 million square kilometers and nine countries. It has a flow rate of more than 40,000 cubic meters per second, and it is the second-largest basin in the world.