Adaptation
The way animals change their behaviour or their bodies so that they are best equipped to survive in a certain environment.

Canyon
A very deep valley with steep sides, often with a stream flowing through it.

Dam
A barrier of material that is built across a river to create a body of water.

Drought
A long period of time without rain.

Fertiliser
Chemicals or animal waste that help to enrich the soil, and make crops grow better.

Floodplain
A flat area of land next to a river which is covered in water when the river floods.

Highlands
An area of high ground that is a long way above sea level. A good example of this is mountains from where water flows down on its way to rivers.

Irrigation
Different ways of watering the land to help crops grow.

NASA
Stands for 'National Aeronautics and Space Administration', based in the USA. NASA launches rockets and satellites into space to discover more about life on Earth, the atmosphere and other planets. Visit http://kids.earth.nasa.gov/ to learn more.

Reservoir
A man-made lake formed behind a dam.

River Basin
The area of land that a river gets it water from. It is shaped a little like a sink so that all the water drains down to the river.

Silt
Very fine mud or clay picked up from the land and carried by rivers until they are dropped when the flow of the water slows down.

Source
The starting point of a river.

Swamp
An area of land that is always wet and soggy.

Tributary
A small river or stream that feeds a bigger one.

Upstream
In the opposite direction to the water's current, away from a river's mouth and towards its source.