Le Cycle de l'eau

Summary

This script discusses the critical nature of water conservation, especially in the context of space travel where each person consumes approximately 5 liters daily for drinking, food, and hygiene. It emphasizes the scarcity of fresh water on Earth, constituting only 0.023% of its mass, with accessible fresh water for humans and agriculture being even more limited. The script outlines the water cycle, from evaporation over the oceans to condensation and precipitation, highlighting the importance of preserving this vital resource.

Takeaways

• 💧 The average person on board a spacecraft uses about 5 liters of water per day for drinking, eating, and washing.
• 🚀 Water is a precious resource in space, with desalination units used to convert seawater into drinkable water to avoid carrying heavy water bottles from the start.
• 🌍 Earth appears to be covered by water, but in reality, water only represents 0.023% of Earth's mass.
• 🌊 If all of Earth's water were gathered together, it would fit into a sphere with a diameter of 1,385 km.
• 🏔 Freshwater makes up an even smaller portion of Earth's water, primarily stored in polar ice caps and underground, inaccessible to humans.
• 🌱 Freshwater available for the world's 7.5 billion people, agriculture, and livestock represents a tiny fraction, equivalent to seven small marbles.
• 🌧 The water cycle begins with the sun's rays causing evaporation from oceans, with additional water vapor coming from plant transpiration, especially forests.
• ☁️ When water vapor encounters cooler temperatures, it condenses into droplets, forming clouds.
• 🌨 When these droplets become too heavy, they fall as rain or snow, with a small part infiltrating the soil, eventually flowing into lakes, rivers, and returning to the ocean.
• 💦 The freshwater we use is extracted from rivers and aquifers before joining the oceans, where the cycle of evaporation, condensation, and precipitation begins anew.
• 🌿 The importance of the water cycle is highlighted, showing the continuous movement of water from the Earth's surface to the atmosphere and back.

Q & A

How much water is typically consumed per person per day on board?

Approximately 5 liters per person per day is used for food, drinking, and washing.

Why is water used directly from the sea for washing?

Using seawater directly for washing reduces the need to carry heavy bottles of water from the start.

What is the purpose of having two desalinators on board?

Having two desalinators ensures a backup in case one fails, providing a reliable source of drinking and cooking water from seawater.

What percentage of the Earth's surface is covered by water?

Water covers about 70% of the Earth's surface.

What percentage of the Earth's mass is made up of water?

Water represents only 0.023% of the Earth's mass.

If all the Earth's water was gathered together, how large would it be?

If all the Earth's water was gathered, it would fit into a sphere with a diameter of 1300 km.

How much of the Earth's water is freshwater, and where is it primarily stored?

Freshwater constitutes a much smaller amount and is primarily stored in glaciers at the poles or in the Earth's crust, out of reach for humans.

What is the volume of freshwater available for human use, agriculture, and livestock?

The available freshwater for human use, agriculture, and livestock is represented by just seven small spheres, with one sphere being only 60 km in diameter.

How does the water cycle begin?

The water cycle begins with the action of the sun's rays, causing evaporation from the oceans and transpiration from plants, particularly forests.

What happens to the water vapor in the atmosphere?

When water vapor in the atmosphere encounters cooler temperatures, it condenses into tiny droplets, forming clouds.

How does water return to the Earth's surface from the atmosphere?

Water returns to the Earth's surface from the atmosphere in the form of precipitation, such as rain or snow.

What happens to the water that falls on the ground?

Some of the water that falls on the ground seeps into lakes, rivers, and eventually returns to the ocean, while another part accumulates in glaciers or infiltrates into groundwater, starting the cycle again.