Text Description of the USGS Water Cycle Diagram

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Text Description of the Illustration

The illustration depicts an expansive landscape encapsulating the major pools and fluxes of water on Earth. It is drawn from a high angled perspective that makes features at the bottom of the illustration appear close and features toward the top of the illustration appear far away. There is a large landmass in the central and right part of the illustration, and an ocean to the left. Both the land and the ocean extend into the distance. In the foreground, the front and right side of the landscape are cut away to reveal the subsurface. Water is shown in a bright blue, and the background landscape is greyscale.

Where the landscape meets the ocean there is a coastal plain with wetlands and a small city. Moving inland from the coast, the plain begins to rise and meets the base of a coastal mountain range. In the distance, on the leeward side of the range, there is an arid basin with a small city and a terminal saline lake. The basin is ringed by mountains, and to its right, high mountain peaks form a range that extends eastward, forming the horizon. Large clouds above the mountains are generating precipitation, and the high peaks are covered in snow. A glacier has formed down one valley, and the meltwater from the glacier forms a braided river that drains across the landscape into the foreground feeding back into the ocean. Further to the right in the distant high mountains, seasonal snowpack melts into streams that flow into a man-made reservoir. The outflow from the reservoir feeds a river that drains into an agricultural valley, where water from the river and groundwater are used to irrigate fields of crops. The wells that pump groundwater are visible because the landscape is cut away to display the subsurface. The wells access water from aquifers at different depths beneath the surface. On the surface of the landscape, the river meanders leftward through the valley, flowing through rangeland that is used to graze livestock. It continues into the central foreground of the illustration, passing through an industrial area where factories, mining operations and a thermoelectric power plant use river water for their operations. Finally, it flows past a large city on the coast and back into the ocean at the left of the illustration.

 

Diagram Inset Text

The Water Cycle

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, saline (salty), or a mix (brackish). Water moves between the places it is stored. Water moves at large scales and at very small scales. Water moves naturally and because of human actions. Human water use affects where water is stored, how it moves, and how clean it is. 

Pools store water. 96% of all water is stored in oceans and is saline. On land, saline water is stored in saline lakes. 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 the 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, within cracks and pores in the rock.   

Fluxes move water between pools. 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. It can return to the surface through natural groundwater discharge into rivers, the ocean, and from springs. 

We alter the water cycle. 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. The amount of water that is available depends on how much water is in each pool (water quantity). It also depends on when and how fast water moves (water timing), how much water we use (water use), and how clean the water is (water quality). 

We 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. Climate change is affecting the water cycle. It is affecting water quality, quantity, timing, and use. It is causing ocean acidification, sea level rise, and more extreme weather. By understanding these impacts, we can work toward using water sustainably. 

Visit www.usgs.gov/water-cycle for definitions.