River
The river is a great natural drainage. River sources can be from lakes, springs or rivers. From its source all the rivers are down the hill, and it is the usual way of rainwater that goes down the land to flow to the sea or large reservoirs like lakes. The mouth, or the end of the river in the sea is called the estuary, while the cause is called the ulu. River water is usually limited in a single channel, consisting of a river bottom between the two banks on the left and right. Most rain on land will pass through the river on its way to the sea. A river usually consists of several tributaries that join.