1. WATER IN NATURE.
1.RIVERS.
Rivers consist of fresh water, which flows from high land down to lower land. A river flows to the sea, to a lake or to
another river. Tributaries are small rivers that join main rivers.
To find out about a river, we have to look at:
• The length: The distance between the source and the mouth of the river.
• The course: The journey it makes.
• The volume: The amount of water that it carries.
The course of a river has three parts:
1. The upper course: It is small and narrow. The volume of water is small. This part is near the source and
the river flows quickly because it is flowing downstream.
2. The middle course: It usually goes through a valley. The river is wider and deeper and has more water.
The tributaries usually join here.
3. The lower course: It is near its end. The water flows slowly because the land is usually flat. The river is
even wider and flows slowly.
A dam is a thick wall that is build across a river to store water. A reservoir is an amount of water that is stored by a
dam.
Dams and reservoirs have many uses. For example, they provide drinking water for towns nearby.
2. GROUNDWATER.
The water from snowmelt, rain and rivers filters through the soil and between the rocks. It forms deposits of water
under the ground.
3.LAKES AND PONDS.
A lake is a large mass of fresh water. It forms a depression in the surface of the Earth. It is filled from rain water.
Many lakes also get water from a river that ends in the lake. A small lake is called a pond.
4.SALT WATER.
An ocean is a very large mass of salt water. There are 5 oceans: The Atlantic. The Pacific, the Indian, the Arctic and
the Antarctic. A smaller mass of salt water is called a sea, like the Mediterranean Sea or the Cantabric Sea in Spain.