• Water Science School HOME • Water Cycle Diagrams • Glossary of Water Cycle Terms • Water Pools and Fluxes Data Tables Show
What is the water cycle?Viewed from space, the most striking feature of our planet is the water. In both liquid and frozen form, it covers 75% of the Earth's surface. It fills the sky with clouds. Water is practically everywhere on Earth, from inside the planet's rocky crust to inside the cells of the human body (NASA). What's important to keep in mind is that all of this water is in constant motion across our planet.Credit: NASA The water cycle describes where water is on Earth and how it moves. Water is stored in the atmosphere, on the land surface, and below the ground. It can be a liquid, a solid, or a gas. Liquid water can be fresh or saline (salty). Water moves between the places it is stored. Water moves at large scales,
through watersheds, the atmosphere, and below the Earth's surface. Water moves at very small scales too. It is in us, plants, and other organisms. Human activities impact the water cycle, affecting where water is stored, how it moves, and how clean it is. Pools store waterOceans store 96% of all water on Earth. Ocean water is saline, meaning it’s salty. On land, saline water is stored in saline lakes. The rest of the water on Earth is fresh water. Fresh water
is stored in liquid form in freshwater lakes, artificial reservoirs, rivers, and wetlands. Water is stored in solid, frozen form in
ice sheets and glaciers, and in snowpack at high elevations or near Earth's poles. Water vapor is a gas and is stored as atmospheric moisture over the ocean and land. In the soil, frozen water is stored as permafrost and liquid water is stored as
soil moisture. Deeper below ground, liquid water is stored as groundwater in aquifers. Water in groundwater aquifers is found within cracks and pores in the rock. Fluxes move water between poolsClouds are formed by water condensing in the atmosphere. When the water is released back to the Earth's surface we experience precipitation. Both condensation and precipitation are important fluxes in our water cycle.Credit: Tobias Hämmer | Pixabay As
it moves, water can change form between liquid, solid, and gas. Circulation mixes water in the oceans and transports water vapor in the atmosphere. Water moves between the atmosphere and the surface through evaporation, evapotranspiration, and
precipitation. Water moves across the surface through snowmelt, runoff, and
streamflow. Water moves into the ground through infiltration and groundwater recharge. Underground, groundwater flows within
aquifers. Groundwater can return to the surface through natural discharge into rivers, the ocean, and from springs. What drives the water cycle?Water moves naturally and because of human actions. Energy from the sun and the force
of gravity drive the continual movement of water between pools. The sun’s energy causes liquid water to evaporate into water vapor. Evapotranspiration is the main way water moves into the atmosphere from the land surface and oceans. Gravity causes water to flow downward on land. It causes rain, snow, and hail to fall from clouds. Humans alter the water cycleA reservoir is a human-made lake. Reservoirs form when a dam is built on a river, allowing water to pool behind the dam.Credit: Thomas Ehrhardt | Pixabay In addition to natural processes, human water use affects where water is stored and how water moves. We redirect rivers. We build dams to store water. We drain water from wetlands for development. We use water from rivers, lakes, reservoirs, and groundwater aquifers. We use that water to supply our homes and communities. We use it for agricultural irrigation and grazing livestock. We use it in industrial activities like thermoelectric power generation, mining, and aquaculture. We also affect water quality. In agricultural and urban areas,
irrigation and precipitation wash fertilizers and pesticides into rivers and groundwater. Power plants and factories return heated and contaminated water to rivers. Runoff carries chemicals,
sediment, and sewage into rivers and lakes. Downstream from these sources, contaminated water can cause harmful algal blooms, spread diseases, and harm habitats for wildlife. The water cycle and climate changeClimate change is actively affecting the water cycle. It is impacting water quantity and timing. Precipitation patterns are changing. The frequency, intensity, and length of extreme weather events, like floods or droughts, are also changing. Ocean
sea levels are rising, leading to coastal flooding. Climate change is also impacting water quality. It is causing ocean acidification which damages the shells and skeletons of many marine organisms. Climate change increases the likelihood and intensity of
wildfires, which introduces unwanted pollutants from soot and ash into nearby lakes and streams. What determines water availability?Humans and other organisms rely on water for life. The amount of water that is available depends on how much water there is in each pool (water quantity). Water availability also depends on when and how fast water
moves (water timing) through the water cycle. Finally, water availability depends on how clean the water is (water quality). By understanding human impacts on the water cycle, we can work toward using water sustainably. Read more about the components of the water cycle in more detail:Atmosphere · Condensation · Evaporation · Evapotranspiration · Freshwater lakes and rivers · Groundwater flow · Groundwater storage · Ice and snow · Infiltration · Oceans · Precipitation · Snowmelt · Springs · Streamflow · Sublimation · Surface runoff Which of the following trophic levels represents a primary producer in an aquatic food chain?First trophic level.
The plants in this image, and the algae and phytoplankton in the lake, are primary producers. They take nutrients from the soil or the water, and manufacture their own food by photosynthesis, using energy from the sun.
Which of the following types of organisms are required to complete the nitrogen cycle including the process of denitrification responses?The final aspect of the nitrogen cycle is the process of denitrification. This process is performed by a variety of microscopic bacteria, fungi, and other organsims. Nitrates in the soil are broken down by these organsisms, and nitrogen is released into the atmosphere. This complete the cycle.
What represents a carbon sink that holds carbon compounds for the shortest period of time?The shortest carbon sink sink is found in the tropical rainforests where nutrient cycling happens very quickly. Plants in this region can grow, die, and decompose within a year which means that very little carbon might get stored over the long term.
Which of the following terrestrial biomes has the lowest primary productivity per unit area?So, the correct option is 'Open Ocean'.
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Which of the following best identifies a key component of the hydrologic cycle that powers the movement of water and is missing from the diagram terrestrial animals?
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