Answer:
A river system is made up of a river and its tributaries.
What is a river system?
A river system is a term used to describe the broader networks of streams, lakes, and rivers that are tributaries and distributaries of a larger river. For instance, the Mississippi River system includes the Ohio, Red, and Missouri rivers, all of which drain into the Mississippi River. Due to its interconnectedness, the condition of one river may have an effect on the health of the other rivers in the same river system. A river system can also include other types of terrain, such as the wetlands and flood plains that are affected by a major river and its tributaries and distributaries. The majority of the time, rivers have a primary source, such as snowmelt from a mountain that cascades into a number of streams, which eventually merge to form a river that empties into a much bigger river. This is an illustration of a river network. River systems are ecosystems from an environmental perspective, and if even one component of the system is contaminated or destroyed, it may have a severe impact on things like water quality and the health of plants and animals. For instance, the effects of high pollution levels or prolonged drought near a river's source will be felt throughout the rivers and lands that make up the river system.
An example of this is the Amazon River in Brazil (South America).