The Water Cycle
The following video provides a schematic summary of the water cycle.
Video: The Water Cycle (1:23) This video is not narrated and is set to music.
The hydrologic cycle describes the large-scale movement of water between reservoirs including the ocean, rivers and lakes, the atmosphere, ice sheets, and underground storage or groundwater.
A diagram titled "The Water Cycle," created by the U.S. Geological Survey and the U.S. Department of the Interior. It illustrates the continuous movement of water on, above, and below Earth's surface. The diagram features a landscape with mountains, a forest, and an ocean under a partly cloudy sky with a sun. Blue arrows indicate the flow of water through various processes: evaporation from the ocean, condensation in the atmosphere, precipitation as rain or snow, water storage in the atmosphere, ice, and snow, snowmelt runoff to streams, surface runoff, streamflow, freshwater storage in springs, infiltration into the ground, ground-water discharge, and ground-water storage. The ocean is labeled as "Water storage in oceans."
- Diagram Overview
- Title: The Water Cycle
- Creators: U.S. Geological Survey, U.S. Department of the Interior
- Type: Illustrated diagram of water movement
- Landscape Features
- Mountains: Left side, with snow
- Forest: Central area, green with trees
- Ocean: Right side, blue with waves
- Sky: Partly cloudy with a sun on the right
- Water Cycle Processes (Indicated by Blue Arrows)
- Evaporation
- Position: From the ocean to the atmosphere
- Condensation
- Position: In the atmosphere, forming clouds
- Precipitation
- Position: From clouds to the ground as rain or snow
- Water Storage in the Atmosphere
- Position: Within clouds
- Water Storage in Ice and Snow
- Position: On mountains
- Snowmelt Runoff to Streams
- Position: From mountains to streams
- Surface Runoff
- Position: From land to the ocean
- Streamflow
- Position: Through rivers and streams
- Freshwater Storage
- Label: Spring
- Position: Near the base of mountains
- Infiltration
- Position: From surface to underground
- Ground-water Discharge
- Position: From underground to the ocean
- Ground-water Storage
- Position: Below the surface
- Water Storage in Oceans
- Position: Right side of the diagram
- Evaporation
- Visual Elements
- Arrows: Blue, showing the direction of water movement
- Colors: Blue for water, green for land, white for clouds and snow
- Additional Notes
- Sun: Top right, indicating solar energy driving the cycle
- Labels: Clearly marked for each process and storage type
Water evaporates from bodies of water such as the ocean and lakes to form clouds. The moisture in clouds ultimately falls as rain or snow, some of which returns back to the ocean, lakes, and rivers. The remainder percolates into the soil, where it reacts with organic material and minerals and ultimately moves downwards to form groundwater. The amount that percolates depends strongly on evaporation as well as soil moisture, as shown in the video below.
Video: NASA Land Globe Animation (1:00) This video is not narrated.
As rain and snow fall to earth over the land, the increase in water competes with the loss of water due to daylight evaporation.
Precipitation:
0.01 to 10 millimeters per hour in steps of (0.01, 0.1, 1, 10)
Different kinds of soil retain different amounts of water in the ground, so the flow of rivers and the filling of underground aquifers can be hard to predict.
Rate of change of total land water:
-1.5 to 1.5 grams per square meter per second in steps of (0.5)
Freshwater used for drinking, agriculture, and industry derives dominantly from rivers, lakes, and groundwater, with the latter reservoir accounting for approximately 30 percent of freshwater on the earth’s surface by % of potable (i.e., safe drinking) water. In the US, 86% of households derive water from public suppliers, and 14% supply their own water from wells. Nevertheless, households utilize only one percent of water extracted, the remaining 99% of water is supplied to industry (4%), agriculture (37% compared to 69% worldwide), and thermoelectric power plants (41%). Water use in most areas of the US has increased substantially over the last century.