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The water cycle, also known as the hydrologic cycle, is the continuous movement of water on, above, and below the surface of the Earth. This immense system, driven by energy from the sun, is essential for all life on our planet. The Earth's water is constantly in motion, changing between liquid, vapor (gas), and ice (solid) states. The cycle has no starting point, but it can be best understood by following water through its various processes: evaporation, condensation, precipitation, and collection. While the total amount of water on Earth remains relatively constant over time, its distribution among the major reservoirs—ice, fresh water, saline water, and atmospheric water—is variable.

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Evaporation is the primary process by which water changes from a liquid to a gas or vapor, and it is the main pathway for water to enter the atmosphere. The sun's energy heats water in oceans, lakes, and rivers, causing it to evaporate. A significant amount of water vapor also enters the atmosphere through transpiration, a process where plants absorb water through their roots and then release it as vapor through small pores on the undersides of their leaves. The combined process of evaporation and transpiration is often referred to as evapotranspiration.

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Once in the atmosphere, the water vapor rises, cools, and undergoes condensation. Condensation is the process by which water vapor in the air is changed into liquid water. As warm, moist air rises, it cools and is no longer able to hold all of its water vapor. The excess vapor condenses to form tiny water droplets or ice crystals. These particles are very small and light, and they group together to form clouds. Clouds are simply visible masses of condensed water vapor.

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When so much water has condensed that the air cannot hold it anymore, the clouds get heavy and the water falls back to the Earth in the form of precipitation. Precipitation can occur in various forms, including rain, snow, sleet, or hail, depending on the temperature of the atmosphere. Most precipitation falls back into the oceans, but a significant portion falls over land. Once it reaches the ground, the water's journey continues in several ways.

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The final stage of the cycle is collection. The precipitation that falls on land can be stored on the surface in lakes, rivers, or as ice caps and glaciers. It can also be absorbed into the ground through a process called infiltration. This groundwater can be stored in underground aquifers for long periods, or it can slowly flow and eventually seep back into rivers and oceans. Water that does not get absorbed by the ground flows over the land as surface runoff, which travels down slopes due to gravity, collecting in rivers and streams that eventually carry it back to the oceans. From these collection points, the sun's energy once again powers evaporation, and the cycle continues its perpetual journey.

Paragraph 1

The water cycle, also known as the hydrologic cycle, is the continuous movement of water on, above, and below the surface of the Earth. This immense system, driven by energy from the sun, is essential for all life on our planet. The Earth's water is constantly in motion, changing between liquid, vapor (gas), and ice (solid) states. The cycle has no starting point, but it can be best understood by following water through its various processes: evaporation, condensation, precipitation, and collection. While the total amount of water on Earth remains relatively constant over time, its distribution among the major reservoirs—ice, fresh water, saline water, and atmospheric water—is variable.

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Evaporation is the primary process by which water changes from a liquid to a gas or vapor, and it is the main pathway for water to enter the atmosphere. The sun's energy heats water in oceans, lakes, and rivers, causing it to evaporate. A significant amount of water vapor also enters the atmosphere through transpiration, a process where plants absorb water through their roots and then release it as vapor through small pores on the undersides of their leaves. The combined process of evaporation and transpiration is often referred to as evapotranspiration.

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Once in the atmosphere, the water vapor rises, cools, and undergoes condensation. Condensation is the process by which water vapor in the air is changed into liquid water. As warm, moist air rises, it cools and is no longer able to hold all of its water vapor. The excess vapor condenses to form tiny water droplets or ice crystals. These particles are very small and light, and they group together to form clouds. Clouds are simply visible masses of condensed water vapor.

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When so much water has condensed that the air cannot hold it anymore, the clouds get heavy and the water falls back to the Earth in the form of precipitation. Precipitation can occur in various forms, including rain, snow, sleet, or hail, depending on the temperature of the atmosphere. Most precipitation falls back into the oceans, but a significant portion falls over land. Once it reaches the ground, the water's journey continues in several ways.

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The final stage of the cycle is collection. The precipitation that falls on land can be stored on the surface in lakes, rivers, or as ice caps and glaciers. It can also be absorbed into the ground through a process called infiltration. This groundwater can be stored in underground aquifers for long periods, or it can slowly flow and eventually seep back into rivers and oceans. Water that does not get absorbed by the ground flows over the land as surface runoff, which travels down slopes due to gravity, collecting in rivers and streams that eventually carry it back to the oceans. From these collection points, the sun's energy once again powers evaporation, and the cycle continues its perpetual journey.