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Which is the world's longest river?

The River Nile in East Africa. It is 6670 kilometres long and flows from two sources in Burundi to the Mediterranean Sea.

Which river carries the most water?

The Amazon in South America. It carries one fifth of the world's river water.

How are waterfalls formed?

The river flows along a bed of hard (impermeable) rock, into an area of soft (permeable) rock. A cascade of water is formed as the water erodes away the soft rock more quickly than the hard rock. Underground caves are formed when rocks (such as limestone) allow water to pass through them.

What is acid rain?

It's pollution caused by the burning of fossil fuels in power stations, factories and vehicles. When fossil fuels like coal, oil and petrol are burned they give off sulphur dioxide and nitrogen. This dissolves in clouds and falls to Earth as acid rain, damaging trees, buildings and wildlife.

How do we make electricity from water?

A dam is built to store the water. It is pumped to a power station nearby where there are turbines, which are like giant fans. The water turns the blades of the fan and as it turns it generates electricity.