Water Cycle-Stages of the Water Cycle

Introduction to Water Cycle

Water is an essential component of life on Earth. Water and ice cover approximately 75% of our planet. The oceans contain approximately 97 percent of the water on Earth. Polar ice caps and glaciers store about 1.7 percent of the world’s water. Rivers, lakes, and soil contain about 1.7 percent. Water vapor constitutes only 0.001 percent of the Earth’s atmosphere. All these water sources are connected by the water cycle.

The water cycle is the non-stop process that connects all that water. It joins the oceans, land, and atmosphere of the Earth.

The water cycle on Earth began approximately 3.8 billion years ago, when rain fell on a cooling Earth, forming the oceans. The rain was caused by water vapor escaping from the Earth’s molten core into the atmosphere. The sun’s energy assisted in powering the water cycle, and Earth’s gravity prevented water in the atmosphere from leaving the planet.

Water Cycle:

The water on Earth is constantly moving, and the natural water cycle also called the hydrologic cycle, explains the uninterrupted movement of water on, above, and below the Earth’s surface. Water is constantly changing states, from liquid to vapor to ice, with these processes occurring in the blink of an eye and over millions of years.

The water cycle refers to the process by which water evaporates and falls on Earth as rain before flowing back into the sea via rivers.

There are 6 stages of the water cycle. They are,

• Evaporation
• Condensation
• Precipitation
• Infiltration
• Percolation
• Runoff

These specific steps cause water to circulate between oceans, the atmosphere, and the land.

Oceans:

If you look closely at this image, you will notice that it is blue. It is all water.

The oceans are by far the largest reservoir of water on the planet, accounting for over 96 percent of all water on the planet.

The oceans are critical to the water cycle because they provide nearly all of the water that evaporates from liquid to water vapor (forming clouds).

Atmosphere:

The atmosphere is all the air that extends from the bottom of an ant’s leg up to the point where there is no more air – many miles in the sky. The air outside may appear to be empty, but it is packed with molecules, including water molecules (water vapor).

The water in the air rises high into the sky and condenses into clouds, which float away in search of a picnic to rain on. The atmosphere is a superhighway in the sky that transports water all over the planet.

Stages of the Water Cycle

With the heat of the Sun, water evaporates from the hydrosphere (oceans, seas, rivers, lakes, and ponds) and forms clouds.

1. Evaporation:

Water can be found in lakes, oceans, swamps, soil, and all living creatures and plants. Water molecules become excited and spread out when heat is applied from the Sun, exertion, or artificial means.

Evaporation is the process by which water rises into the air and forms clouds of water vapor because of density loss.

Water normally evaporates when it reaches the boiling point, which is around one hundred degrees Celsius.

However, because there is less pressure holding the water molecules together in places with lower air pressure and humidity, far less heat energy is required to evaporate the water.

Water evaporated from the oceans is not salty because salt is too dense and heavy to rise with the water vapor, just as water from rivers and lakes is not salty.

Snow and ice can become water vapor without first becoming water. This is known as ‘sublimation‘, and it occurs because of low humidity and dry winds. This is most common at mountain peaks or other high points because the lower air pressure requires less energy to sublimate the ice into water vapor.

Mount Everest, for example, has all the necessary components for sublimation, including strong sunlight, low temperatures, low air pressure, strong wind, and low humidity. If you have ever seen dry ice with a fog pouting off it, you have seen sublimation in action.

The process by which water evaporates from the leaves of a plant is known as evapotranspiration. Because of the vast areas covered by plants and trees on the planet, this process produces a significant portion of the water in the atmosphere. While lakes, oceans, and streams produce approximately 90% of the world’s water vapor, the remaining ten percent is made up of various plant life.

2. Condensation:

Clouds are blown over the land by the wind, where they are cool enough to fall as rain.

When rising water vapor comes into contact with cooler air higher in the atmosphere, it cools significantly. The vapor condenses into a cloud, which is carried around the world by shifting air currents and winds.

When water vapor cools to temperatures above zero degrees Celsius, it condenses as water. Water vapor will begin to condense on the surface of tiny dust and dirt particles that rise with the vapor during the evaporation process. These tiny droplets will begin to collide and merge, forming a larger droplet.

3. Precipitation:

When a droplet becomes large enough, gravity pulls it down faster than the updraft in the cloud, causing the droplet to fall out of the cloud and onto the ground below. This is known as ‘precipitation,’ or – more colloquially – rainfall.

If precipitation occurs in extremely cold or low-pressure conditions, these water droplets will frequently crystallize and freeze. As a result, the waterfalls as solid ice, also known as hail or snow. If the conditions are in between those of snow and rain, the droplets will fall as icy cold, half-frozen water known as sleet.

4. Infiltration:

Rainwater is absorbed into the ground through a process known as ‘infiltration.’ Soil and other porous materials can absorb a large amount of water in this manner, whereas rocks and other harder substances can only retain a small amount.

Springs and pumps bring groundwater back to the surface. It is employed in agriculture, industry, and the home. After that, the water evaporates into the atmosphere. It also evaporates from the ground, snow, and reservoirs.

5. Percolation

When water percolates through the soil, it moves in all directions until it either seeps into nearby streams or sinks deeper into what is known as ‘groundwater storage.’ This is where water that does not evaporate or seep out joins up under the ground, saturating the smallest nooks and crannies of rock and soil. These formations, also known as aquifers, explain why the ground beneath the topsoil is sometimes damp or sodden.

When an aquifer becomes too full, it begins to leak onto the surface, forming what is commonly referred to as a ‘spring.’ These are frequently found in porous or brittle rock formations that can crack because of slightly acidic rainfall. If the water is near a volcano or other natural source of thermal energy, it will form a hot spring.

6. Runoff

After the water has fallen and saturated the soil or melted the snow, the water follows gravity and falls down any hills, mountains, or other inclines to form or join rivers. This is known as ‘runoff,’ and it is how water settles in lakes before returning to the ocean. The waterfalls vary in height depending on the incline of the area from which they fall, and when several threads of water meet, they form a stream.

The flow direction of water is known as ‘streamflow,’ and it is central to the concept of currents within rivers and streams. Depending on their proximity to the ocean, these streams and rivers will eventually run off to form lakes or rejoin the ocean.

Because of the amount of water stored in snow or ice, a sudden increase in heat can cause flooding as the water melts and runs off at an alarming rate. Therefore, flooding is so common in the spring after a particularly cold and harsh winter.

When the snowfall is more than evaporation or sublimation, the ice compacts densely to form ice caps. The ice caps and glaciers in the world’s coldest regions are the largest collections of ice on the planet, and they are slowly shrinking as the water in which they sit warms.

This occurs cyclically, with no beginning or end. While precipitation occurs in one part of the world, evapotranspiration occurs in another. The water cycle never ends, which is why the oceans remain level, clouds are always present somewhere in the sky, and drinkable water does not suddenly run out.