There are four settled societies that each developed agriculture independently along major rivers that are traditionally considered the early river valley civilizations. The are the Mesopotamian civilizations, the Nile River civilizations, the Indus River civilizations, and the Yellow and Yangtze River civilizations.
The answer is a stream. The water leaves a lake through a stream to maintain the freshness of the lake waer. A stream is where the water flows downhill from an open lake. An open lake is where the water flows constantly so that the water is fresh.
