Liz Bonnin introduces a clip explaining the water cycle.
LIZ BONNIN: Hi, Liz Bonnin here. I'm a science, wildlife and natural history presenter and I'm passionate about conservation and the natural world, and today, we're here on the south coast by the stunning Seven Sisters cliffs, to talk to you about physical geography.
Now physical might make you think that the subject only covers solid things, like rocks and landscapes, but actually it also requires an understanding of the things that have an impact on our surroundings, and that is why we're now going to look at water.
Water is everywhere around us, as vapour, rain or clouds in the air, or in rivers and seas, and it's essential for all life, both plants and animals, to survive.
And it's constantly moving around in a process called the water cycle.
Now that's got nothing to do with floating bicycles, which is a shame, but in this clip Professor Ian Stewart does get to go on very impressive ride in a para-glider.
PROFESSOR STEWART: The fresh water that we depend on begins its life in the oceans. As the sun's rays beat down on the surface of the sea they heat the water molecules until some evaporate. It's the start of an extraordinary journey.
You know, when water evaporates it feels like it vanishes into thin air, but although we barely notice it, water molecules are suspended around us all the time. Just that we're only aware of it when they clump together as cloud.
At any one time, less than a thousandth of the world's fresh water is up here in the atmosphere. It may not seem much, but this is what spreads water from the seas to the land.
A water molecule doesn't hang around up here for very long. In fact it spends less time up here in the atmosphere than in any other time in its journey. A mere nine days until a typical water molecule crashes to earth as rain.
For most of us, rain is perhaps the most familiar stage of the water cycle. But, notoriously, the least reliable.
When the water falls as rain, it joins a bigger system cascading and carving its way across the land surface as streams and rivers. Look at that! Water absolutely everywhere!
Rivers and rain are the part of the water cycle that we depend on. Whoa! And yet they're only a tiny proportion of the world's fresh water. A measly 2% of all fresh water on the planet.
The rest of the Earth's fresh water is locked away down there, on the ground. (As the para-glider lands) Wahey! Oh, what a landing. The vast majority of it is stored as ice.
Most of the rest seeps deep into the earth, where it's known as ground water. Hidden away down here is the planet's second largest store of fresh water. But in the end, all water arrives back in the oceans, and the cycle begins again.
LIZ BONNIN: So there you go. Most of the Earth's fresh water supplies, over 65%, are frozen in the ice caps and glaciers. There's a huge amount, over 30%, trickling around in the ground and rocks beneath us, and rivers and streams only account for tiny amount. A drop in the ocean!
Liz Bonnin introduces the water cycle and explains how water is constantly moving around Earth.
Ian Stewart explains evaporation and that water is constantly suspended in the atmosphere, yet we only notice it when it falls as rain.
Once it’s fallen as rain, water joins a far bigger system - working its way across the landscape.
A huge waterfall is shown to demonstrate this, reminding us that rivers and rain are the parts of the water cycle that we depend on.
Yet, only 2% of the world’s freshwater is available in rivers and rain - most is locked away in ice or stored deep in the earth as groundwater.
Eventually, all water ends up in oceans and the cycle begins again.
This short film is from the 鶹Լ series, Physical Geography with Liz Bonnin.
Teacher Notes
This short film could be used to introduce the water cycle and how water moves around a never-ending system.
Students could consider the various stages of the water cycle that are mentioned and how water moves between each stage.
Students could also consider how small a percentage of the global water supply is available as fresh water and the implications of this.
Curriculum Notes
This topic appears in geography at KS3 and KS4 / GCSE in England, Wales and Northern Ireland and National 4/5 in Scotland.
More geography clips with Liz Bonnin:
How does a river change as it travels downstream? video
Liz Bonnin introduces a 鶹Լ archive clip of Sir David Attenborough as he follows the Amazon River downstream.
The erosion of the Grand Canyon. video
Liz Bonnin introduces the Grand Canyon with its complex and very ancient geology.
What coastal management techniques are being used on Hayling Island? video
This short film introduces the coastal management techniques used on Hayling Island in Hampshire.
What is a ‘spit’ and how does it form through longshore drift? video
Presenter Katie Knapman explains how a spit forms through longshore drift and is a dynamic feature- constantly changing the coastline.
The geological significance of the Jurassic Coast. video
A look at the Jurassic coastline and its geological significance with rocks spanning the Cretaceous, Jurassic and Triassic periods.
How has ice and other processes impacted the landscape of Yorkshire? video
Wildlife presenter Julia Bradbury explains how Malham Cove and the limestone pavement formed, highlighting the significance of glaciers on the landscape.
What does the North Norfolk coastline tell us about how glaciation shaped Britain? video
Presenter and biologist Alice Roberts explains how Britain used to be connected to Europe via a land-bridge but has changed with sea-level rise since the last Ice Age.
Glaciation of the Northern Hemisphere. video
Presenter Iain Stewart explains the glaciation of the Northern Hemisphere, looking at the El Capitan rock face.
What evidence is there for a changing climate in the UK? video
Countryfile presenter Tom Heap introduces the idea that the UK climate might be changing, with increased droughts, increased summer temperatures but wetter winters.
The continued impact of plate tectonics on our oceans. video
A look at how our oceans are constantly changing due to the underlying plate tectonics.
What can Anglesey tell us about the plate tectonics of Britain? video
Presenter Nick Crane uses a map to compare the geology of Anglesey to that of the rest of Britain - highlighting the diversity of rock types.
Deforestation and soya growth in Paraguay. video
Simon Reeves visits Paraguay to consider the deforestation that has occurred to grow soy and the challenge of conversation vs exploitation.
