A river system consists of a main river along with its tributaries and distributaries that together drain water from a specific area. It begins at the source, usually in mountains or highlands, and flows downhill due to gravity until it reaches a mouth such as a sea, lake, or another river. Tributaries add water and sediments, increasing the river’s volume. The river system plays a major role in shaping landforms through erosion, transportation, and deposition. Famous river systems like the Ganga support agriculture, settlements, and ecosystems along their courses.