Where is the source of a river?

Rivers are natural streams of water. They are formed by the movement of water from high ground to lower ground and then usually to the sea. The place where a river begins is called its source. Rivers are constantly changing as they flow over lands and have many different features. They can change shape as they erode the ground at their banks. When rivers eventually meet the sea they may form 'D' shaped masses of channels called deltas.. Small rivers are also called streams, creeks and brooks.