The hydrological Cycle

What is the Hydrological Cycle?

At its very core, the hydrological cycle (previously referred to as the water cycle) is the continuous movement of water from the ground to the atmosphere and back again. During primary school, you understood that this process had three main stages. These stages were: Precipitation, Evaporation and Condensation.

Diagram of The Hydrological Cycle

Alternative Diagram of The Hydrological Cycle

The Processes of The Hydrological Cycle are as follows:

Evaporation: is the process by which a liquid is converted into vapour. This occurs on the surface of a liquid.
Transpiration: is the process by which plants lose water through their leaves. Water vapour escapes through tiny openings called stomata in the leaves.
Evapotranspiration: is the loss of water from the land by evaporation and transpiration.
Condensation: is the process by which vapour is converted into a liquid. In the diagram it refers to water vapour being converted into water droplets in the atmosphere.
Precipitation: refers to any of the forms in which water falls from the atmosphere and reaches the ground including rain, snow or hail.
Interception: is the process where objects such as trees prevent the direct contact of the rain and the ground.
Infiltration: is the process by which water enters the soil.
Surface runoff: is the flow of water on the surface of the Earth into water bodies.
Percolation: is the process by which water moves downward through the soil.
Water Table: is the level at which the ground is saturated with water.
Sublimation: a process in the water cycle where water changes directly from a solid to a gas, without becoming a liquid first.
Desublimation/Deposition: occurs when water vapor turns directly into ice or snow.

It should be noted that the most important processes of The Hydrological Cycle are: evaporation, transpiration, condensation, precipitation, and runoff.

Watch this video to supplement this lesson. It will do a great job of taking you through the diagrams from earlier.

Now that you understand The Hydrological Cycle, we should finally make notice of the world's water supply. With that being said, how much of the world is water?

Seventy percent (70%) is the Earth's surface is water. This leaves the remaining thirty percent (30%) as land space of which humans only occupy roughly under 10% of that.

How is the 70% of water split up? Let's investigate.

Bar Graph breaking down the distribution of water on the Earth's surface

Of the 70% of water around the world, 97% of it is Saline Water (meaning it is located in the oceans) which requires processes like desalination to make it usable. The remaining 3% is fresh water (water that is usable without any processes necessary). However, there's a catch. Of that 3%, 68.7% is frozen in Ice Caps and Glaciers, 30.1% is Ground Water (underground forming the water table that you learned about earlier) and the remaining 0.9% is found in fresh water bodies. Of that Fresh surface water, 87% is Lakes, 11% swamps and 2% is Rivers. Take some time to crunch those numbers then think about your environment and see if you can figure out the distribution of water in your surrounding area. Then ask yourself, is that truly enough to maintain your community?

Use this video to supplement this portion of the lesson.

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