Geography: 6. Water and Rivers

Water and Rivers

Water cycle

The water cycle shows how water moves around the Earth — it never runs out, just keeps changing form.

It starts when the sun heats up water in rivers, lakes, or oceans, turning it into water vapour — this is called evaporation.

The vapour rises and cools down in the sky, forming clouds — this is condensation.

When clouds get heavy, water falls back to the ground as rain, snow or hail — this is precipitation.

Water then flows over the land or soaks into the ground — called run-off and infiltration — and ends up back in rivers and oceans.

The cycle keeps going and is very important for all living things.

Drainage basin features

A drainage basin is the area of land where all the water drains into one river and its tributaries.

The source is where a river begins, often in the hills or mountains.

The mouth is where the river ends, usually flowing into the sea or a lake.

A tributary is a smaller river or stream that flows into a bigger one.

The watershed is the edge of a drainage basin — like the high ground that separates one basin from another.

Understanding drainage basins helps us see how rivers connect landscapes and can affect flooding.

River long profile processes and landforms

A river’s long profile shows how it changes from source to mouth — from steep in the upper course to flat in the lower course.

In the upper course (near the source), rivers are fast, with steep valleys, waterfalls, and rapids.

In the middle course, the river starts to meander (bend) and create wider valleys.

In the lower course, near the mouth, rivers flow slowly and may form floodplains, deltas, or estuaries.

Rivers shape the land through erosion (wearing it away), transport (carrying material), and deposition (dropping material when the river slows down).