The basic components of a river system are the main river, which is the largest river in the system, and its tributaries, which are smaller rivers that flow into the main river. Tributaries can be further divided into sub-tributaries, which are smaller rivers that flow into the tributaries. The area of land that is drained by a river system is known as its catchment or drainage basin.
River systems play an important role in the environment. They provide water for drinking, irrigation, and transportation. They also support a variety of aquatic and terrestrial ecosystems. River systems are also important for their aesthetic and recreational value.
The study of river systems is known as hydrology. Hydrologists study the physical, chemical, and biological characteristics of river systems. They also study the interactions between river systems and the surrounding environment.