River is one part of the hydrological cycle. Water in rivers generally collects from precipitation, such as rain, dew, springs, underground runoff, and in certain countries river water also comes from melting ice / snow. Besides water, the river also flows sediment and pollutants.

At first there were several springs that emitted from the ground. The water that comes out forms small streams. These small streams will eventually become a river. Ice on a melting mountain slope can also become a river. Part of the flowing lake water can also become a river. The river consists of several parts, starting from a spring that flows into a creek. Some tributaries will join to form the main river. Water flow usually borders on a channel with a base and the cliff on the left and right. The end of the river where the river meets the sea is recognized as the river mouth.