What is the Water Cycle in Ecology? Diagram, Steps and Facts

Table of Contents

What is the water cycle?

The water cycle, also termed the hydrological cycle, depicts the continuous movement of water within the Earth and its atmosphere in ecology.

Definition of the water cycle

The water cycle is the movement of water between the atmosphere and land. In more technical terms, the water cycle is the continuous process of water evaporating and condensing on planet Earth.

Water cycle explanation

The water cycle is a complicated system with several processes or steps. It is complicated in the sense that liquid water evaporates into water vapor and condenses to form clouds, and these clouds fall back to the earth’s surface as rain or snow.

Water moves through the lithosphere in various phases. For example, liquid water flows on land known as runoff, and it moves into the ground through a process known as infiltration or percolation to form the groundwater. Groundwater then moves into plants when they take up water for use via their root system. The water then evaporates from plants into the atmosphere, a process known as transpiration.

As regards the movement of water in various phases, solid ice and snow can directly decompose into gaseous water molecules via a process termed sublimation.

The water cycle encompasses energy transfer, which causes temperature changes. Water evaporates, absorbing energy from its surroundings and cooling the environment. It gives off energy and warms the environment whenever it condenses.

These heat transfers have an impact on the climate.

The water cycle’s evaporative phase purifies water, which then refills the land with freshwater. The movement of liquid water and ice transports minerals all over the world. It also plays a role in reshaping the Earth’s geological features through processes such as erosion and sedimentation.

The water cycle is indeed necessary for the survival of most life and ecosystems on Earth.

Water cycle diagram

Water Cycle Diagram
The above is a simple diagram of the water cycle illustrating the movement or circulation of water from the atmosphere to the earth’s surface and back to the atmosphere.

Water cycle steps

  1. Evaporation
  2. Sublimation
  3. Transpiration
  4. Condensation
  5. Precipitation
  6. Runoff
  7. Infiltration

The above are the steps of the water cycle; we will discuss each of the steps below.



The definition of evaporation is termed as the process by which a substance changes from liquid to a gas. Energy is needed for evaporation to occur and it is provided by the sun, atmosphere, or objects on the earth’s surface, such as humans. Everyone has a personal experience with evaporation.

Whenever the body heats up in response to air temperature or exercise, it sweats, secreting water onto the skin. The goal is to cause the body’s heat to evaporate the liquid, reducing the heat and cooling the body. It has the same consequence as when you step out of a shower or a swimming pool.

The coolness you feel is caused by the removal of body heat in order to evaporate the water on your skin.

Examples of Evaporation

  • Sweating of the skin
  • Melting of ice cubes
  • Clothes drying under the sun
  • Hair drying
  • The drying of nail polish
  • Drying-up of water bodies


In this water cycle step, ice directly converts to water vapor rather than liquid water. Sublimation, in addition to evaporation, contributes to the presence of water vapor in the atmosphere. When the temperature is low or the pressure is high, the sublimation process accelerates. The ice sheets of the cryosphere, found in the North and South Poles, as well as mountain ice caps, are the primary sources of water from sublimation. Sublimation is a more gradual process than evaporation.


Transpiration is defined as the evaporation of water from plants via stomata (tiny openings on the undersides of leaves that connect to vascular plant tissues). In simple terms, transpiration is when the water leaves the plant through tiny holes. Transpiring plants use only one percent of the transpired water that passes through them for their growth process.

The other 99% of the water is released into the environment. Transpiration in plants is vital for transporting minerals and hormones across the plant.

Condensation in the water cycle

This step of the water cycle refers to the process by which water vapor in the atmosphere is converted to liquid. Condensation in the atmosphere can manifest as clouds or dew. The process by which water appears on the side of an uninsulated cold drink can or bottle is a simple example of the condensation in the water cycle

Condensation is caused by a difference between two temperatures, that is, the air temperature and the dewpoint temperature. The dew point, in its most basic form, is the temperature at which dew can form; in fact, it is the temperature at which the air becomes saturated if it is kept cool to that level.

Water vapor condenses as a result of any additional cooling. When the air temperature and dew point are both equal, foggy conditions are common.

Condensation is the inverse process of evaporation. Because water vapor has a higher energy level than liquid water, when condensation occurs, the excess energy is released in the form of heat energy.

Examples of condensation in the water cycle

  • Condensation is the cause of ground-level fog
  • It causes fog on cold objects such as the fog accumulating on your glasses when you go from a cold room to the outdoors on a hot, humid day.
  • Condensation plays a big part in the water that drips off the outside of your glass of iced tea, and the water on the inside of your home’s windows on a cold day.

Precipitation in the water cycle

Clouds (condensed water vapor) fall as precipitation as a result of wind or temperature change. This happens when water droplets combine to form larger drops and when the air can no longer hold any more water, it falls as rain, hail, snow, or sleet. Because the temperature is low at high altitudes, the droplets lose their heat energy as is the case with rainfall.

But if the temperature is extremely low (below zero degrees), the water droplets will fall as snow. Besides that, water could fall in the form of drizzle, sleet, or hail; all these forms of precipitation make water enter the lithosphere. Precipitation is the primary means by which we obtain fresh water on Earth.


This occurs when there is an abundance of precipitation and the ground becomes saturated (cannot absorb any more water). Runoff creates rivers and lakes. Although some of the accumulated runoff can evaporate into the atmosphere, the majority of water in rivers and lakes returns to the oceans.

If runoff water only flows into the lake (with no outlet for the water to flow out), evaporation is the only way for water to return to the atmosphere.

The evaporation of this runoff into the atmosphere restarts the hydrologic cycle. Some of the water percolates into the soil to the groundwater, only to be drawn back into the plants for transpiration.


Not all of the runoff of precipitation flows into rivers but is absorbed by plants or evaporates; some penetrate deeply into the soil via a process referred to as infiltration. The water seeps down, raising the level of the groundwater table (pure water).

Water cycle facts

  • Water is an inexhaustible resource that cannot be created or destroyed by man.
  • The sun is an enforcer of the water cycle through the provision of heat that causes water to change state.
  • Water either emits or absorbs energy when it changes from one state to another and moves from one location to another.
  • The process by which water evaporates from plant leaves into the atmosphere is known as transpiration.
  • Condensation occurs when water evaporates into the atmosphere and cools and condenses to form clouds.
  • Aquifers are underground freshwater reservoirs found in rocks and minerals.
  • Groundwater, or water stored beneath the Earth’s surface, can stay in place for thousands of years.
  • Fossil water refers to extremely old groundwater.
  • Water covers approximately 70% of the Earth’s surface.
  • Water can be found not only underground, but also in ice caps, snow, and glaciers.
  • Because water is constantly recycled, the water you drink today may be the same as the water dinosaurs drank millions of years ago.
  • Whenever the clouds become too heavy from collecting water, they discharge it in the form of precipitation.
  • Precipitation takes many forms like rain, sleet, snow, or hail.
  • Water that falls during precipitation either becomes a part of a body of water, such as an ocean or a lake, or it seeps into the ground.
  • Only about 3 percent of the water on Earth is freshwater or drinkable water.

The above-listed points are emphasizing about the simple water cycle facts. It can also be used to explain the water cycle for kids.

Importance of the water cycle

  1. Provision of freshwater.
  2. Purification of water.
  3. Distributes water to all life forms.
  4. Sustains life.
  5. Helps in propelling the biogeochemical cycle (e.g., carbon cycle and nitrogen cycle).
  6. Aid in the regulation of climate.

What is evaporation?

Evaporation is the way or method by which water changes its state from a liquid to a gas or vapor. Evaporation is the primary mechanism by which water moves from the liquid to the water cycle as atmospheric water vapor.

What is transpiration?

Transpiration is the process by which plants emit water vapor through holes in their leaves or simply, it is the method water leave plants to go back into the atmosphere in the form of water vapor.