Summary
The continuous movement of water through evaporation, condensation, precipitation and runoff.
In depth
Evaporation and transpiration raise water into the atmosphere, condensation forms clouds, and precipitation returns it. Runoff and infiltration feed rivers and groundwater. The sun drives the cycle.
Deforestation reduces transpiration and rainfall locally.
Human changes include dams, groundwater extraction, irrigation and land cover change. Residence times range from days (atmosphere) to thousands of years (deep ice, aquifers).
Common mistake: water is not created or destroyed; it is moved between reservoirs.
The oceans hold about 97 percent of water and ice caps 2 percent; freshwater lakes and rivers hold less than 0.01 percent. Residence times vary from days in the atmosphere to thousands of years in deep groundwater and ice. Solar energy drives evaporation, and about 90 percent of evaporation is from the oceans. Transpiration from forests recycles rain within continents, as in the Amazon, where the forest generates a significant part of its own rainfall.
Humans alter the cycle by building dams, draining wetlands, pumping groundwater faster than recharge and changing land cover; warming increases evaporation and intensifies extreme rainfall. Water is also moved virtually in crops and products.
Key idea: water is continuously recycled, but usable freshwater is distributed unevenly in space and time.
Frequently asked questions
What is Water Cycle?
The continuous movement of water through evaporation, condensation, precipitation and runoff.
Which area of biology covers Water Cycle, and how advanced is it?
Water Cycle is one of the 54 topics in Ecology. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Climate Change Ecology, Biomes, Carrying Capacity.
Can you give an example of Water Cycle?
About 97 percent of water is in oceans and under 1 percent is easily usable freshwater.
What should I learn before Water Cycle?
Water Cycle is a Beginner topic, so no earlier topic is required. Other Beginner topics in Ecology that pair well with it include Ecology, Ecosystem, Biotic and Abiotic Factors.
What topics are related to Water Cycle?
The closest topics to Water Cycle are Climate Change Ecology, Biomes, Carrying Capacity, Ecology. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Water Cycle?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Water Cycle. To practise the whole of Ecology, use the Ecology quiz.
How is Water Cycle different from Climate Change Ecology?
Water Cycle: The continuous movement of water through evaporation, condensation, precipitation and runoff. Climate Change Ecology: Warming shifts species ranges, phenology and interactions, creating mismatches in ecosystems. Read both side by side and note what each one explains.
What is a common mistake about Water Cycle?
Water is not created or destroyed; it is moved between reservoirs.
How should I study Water Cycle step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Climate Change Ecology and explain the difference aloud. Finally, take the Ecology quiz and come back to this page for any question you miss.