Current (stream)

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The water in this stream forms varying currents as it makes its way downhill Stream in the redwoods.jpg
The water in this stream forms varying currents as it makes its way downhill

A current, in a river or stream, is the flow of water influenced by gravity as the water moves downhill to reduce its potential energy. The current varies spatially as well as temporally within the stream, dependent upon the flow volume of water, stream gradient, and channel geometry. In tidal zones, the current in rivers and streams may reverse on the flood tide before resuming on the ebb tide.

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Tide Rise and fall of the sea level under astronomical gravitational influences

Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun, and the rotation of the Earth.

Estuary Partially enclosed coastal body of brackish water

An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environments and are an example of an ecotone. Estuaries are subject both to marine influences such as tides, waves, and the influx of saline water and to fluvial influences such as flows of freshwater and sediment. The mixing of seawater and freshwater provides high levels of nutrients both in the water column and in sediment, making estuaries among the most productive natural habitats in the world.

Rip current Narrow current of water that moves directly away from the shore, cutting through the lines of breaking waves

A rip current, often simply called a rip, is a specific kind of water current that can occur near beaches with breaking waves. A rip is a strong, localized, and narrow current of water which moves directly away from the shore, cutting through the lines of breaking waves like a river running out to sea. A rip current is strongest and fastest nearest the surface of the water.

A rip tide, or riptide, is a strong, offshore current that is caused by the tide pulling water through an inlet along a barrier beach, at a lagoon or inland marina where tide water flows steadily out to sea during ebb tide. It is a strong tidal flow of water within estuaries and other enclosed tidal areas. The riptides become the strongest where the flow is constricted. When there is a falling or ebbing tide, the outflow water is strongly flowing through an inlet toward the sea, especially once stabilized by jetties. During these falling and ebbing tides, a riptide can carry a person far offshore. For example, the ebbing tide at Shinnecock Inlet in Southampton, New York, extends more than 300 metres (980 ft) offshore. Because of this, riptides are typically more powerful than rip currents.

Ocean current Directional mass flow of oceanic water generated by external or internal forces

An ocean current is a continuous, directed movement of sea water generated by a number of forces acting upon the water, including wind, the Coriolis effect, breaking waves, cabbeling, and temperature and salinity differences. Depth contours, shoreline configurations, and interactions with other currents influence a current's direction and strength. Ocean currents are primarily horizontal water movements.

Physical oceanography Study of physical conditions and physical processes within the ocean

Physical oceanography is the study of physical conditions and physical processes within the ocean, especially the motions and physical properties of ocean waters.

Thermohaline circulation A part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes

Thermohaline circulation (THC) is a part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes. The adjective thermohaline derives from thermo- referring to temperature and -haline referring to salt content, factors which together determine the density of sea water. Wind-driven surface currents travel polewards from the equatorial Atlantic Ocean, cooling en route, and eventually sinking at high latitudes. This dense water then flows into the ocean basins. While the bulk of it upwells in the Southern Ocean, the oldest waters upwell in the North Pacific. Extensive mixing therefore takes place between the ocean basins, reducing differences between them and making the Earth's oceans a global system. The water in these circuits transport both energy and mass around the globe. As such, the state of the circulation has a large impact on the climate of the Earth.

Body of water Any significant accumulation of water, generally on a planets surface

A body of water or waterbody is any significant accumulation of water, generally on a planet's surface. The term most often refers to oceans, seas, and lakes, but it includes smaller pools of water such as ponds, wetlands, or more rarely, puddles. A body of water does not have to be still or contained; rivers, streams, canals, and other geographical features where water moves from one place to another are also considered bodies of water.

Oyashio Current Cold subarctic ocean current that flows south and circulates counterclockwise in the western North Pacific Ocean

Oyashio, also known as Oya Siwo, Okhotsk or the Kurile current, is a cold subarctic ocean current that flows south and circulates counterclockwise in the western North Pacific Ocean. The waters of the Oyashio Current originate in the Arctic Ocean and flow southward via the Bering Sea, passing through the Bering Strait and transporting cold water from the Arctic Sea into the Pacific Ocean and the Sea of Okhotsk. It collides with the Kuroshio Current off the eastern shore of Japan to form the North Pacific Current. The nutrient-rich Oyashio is named for its metaphorical role as the parent that provides for and nurtures marine organisms.

Ipswich River

Ipswich River is a small river in northeastern Massachusetts, United States. It held significant importance in early colonial migrations inland from the ocean port of Ipswich. The river provided safe harborage at offshore Plum Island Sound to early Massachusetts subsistence farmers, who were also fishermen. A part of the river forms town boundaries and divides Essex County, Massachusetts on the coast from the more inland Middlesex County. It is 35 miles (56 km) long, and its watershed is approximately 155 square miles (401 km2), with an estimated population in the area of 160,000 people.

Streamflow, or channel runoff, is the flow of water in streams, rivers, and other channels, and is a major element of the water cycle. It is one component of the runoff of water from the land to waterbodies, the other component being surface runoff. Water flowing in channels comes from surface runoff from adjacent hillslopes, from groundwater flow out of the ground, and from water discharged from pipes. The discharge of water flowing in a channel is measured using stream gauges or can be estimated by the Manning equation. The record of flow over time is called a hydrograph. Flooding occurs when the volume of water exceeds the capacity of the channel.

A tidal river is a river whose flow and level are influenced by tides. A section of a larger river affected by the tides is a tidal reach, but it may sometimes be considered a tidal river if it has been given a separate name.

Marine currents can carry large amounts of water, largely driven by the tides, which are a consequence of the gravitational effects of the planetary motion of the Earth, the Moon and the Sun. Augmented flow velocities can be found where the underwater topography in straits between islands and the mainland or in shallows around headlands plays a major role in enhancing the flow velocities, resulting in appreciable kinetic energy. The sun acts as the primary driving force, causing winds and temperature differences. Because there are only small fluctuations in current speed and stream location with minimal changes in direction, ocean currents may be suitable locations for deploying energy extraction devices such as turbines. Other effects such as regional differences in temperature and salinity and the Coriolis effect due to the rotation of the earth are also major influences. The kinetic energy of marine currents can be converted in much the same way that a wind turbine extracts energy from the wind, using various types of open-flow rotors.

River Roach River in Essex, England

The River Roach is a river that flows entirely through the English county of Essex. It is one of four main streams that originate in the Rayleigh Hills to the west, and flow east. They then flow towards the centre of the Rochford Basin, a circular feature which may have been caused by an asteroid impact in the Late Oligocene or Early Miocene periods. To the east of Rochford, the river becomes tidal, and is governed by the Crouch Harbour Authority. It joins the River Crouch between Wallasea Island and Foulness Island. To the west of Rochford, there is some doubt as to which of the four streams is officially the Roach.

River Natural flowing watercourse

A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of water. Small rivers can be referred to using names such as stream, creek, brook, rivulet, and rill. There are no official definitions for the generic term river as applied to geographic features, although in some countries or communities a stream is defined by its size. Many names for small rivers are specific to geographic location; examples are "run" in some parts of the United States, "burn" in Scotland and northeast England, and "beck" in northern England. Sometimes a river is defined as being larger than a creek, but not always: the language is vague.

Gulf Stream Warm Atlantic Ocean current

The Gulf Stream, together with its northern extension the North Atlantic Drift, is a warm and swift Atlantic ocean current that originates in the Gulf of Mexico and stretches to the tip of Florida and follows the eastern coastlines of the United States and Newfoundland before crossing the Atlantic Ocean as the North Atlantic Current. The process of western intensification causes the Gulf Stream to be a northwards accelerating current off the east coast of North America. At about 40°0′N30°0′W, it splits in two, with the northern stream, the North Atlantic Drift, crossing to Northern Europe and the southern stream, the Canary Current, recirculating off West Africa.

Estuarine water circulation is controlled by the inflow of rivers, the tides, rainfall and evaporation, the wind, and other oceanic events such as an upwelling, an eddy, and storms. Estuarine water circulation patterns are influenced by vertical mixing and stratification, and can affect residence time and exposure time.

Marine habitats Habitat that supports marine life

Marine habitats are habitats that support marine life. Marine life depends in some way on the saltwater that is in the sea. A habitat is an ecological or environmental area inhabited by one or more living species. The marine environment supports many kinds of these habitats. Marine habitats can be divided into coastal and open ocean habitats. Coastal habitats are found in the area that extends from as far as the tide comes in on the shoreline out to the edge of the continental shelf. Most marine life is found in coastal habitats, even though the shelf area occupies only seven percent of the total ocean area. Open ocean habitats are found in the deep ocean beyond the edge of the continental shelf.

Tidal stream generator

A tidal stream generator, often referred to as a tidal energy converter (TEC), is a machine that extracts energy from moving masses of water, in particular tides, although the term is often used in reference to machines designed to extract energy from run of river or tidal estuarine sites. Certain types of these machines function very much like underwater wind turbines, and are thus often referred to as tidal turbines. They were first conceived in the 1970s during the oil crisis.

Tidal barrage Dam-like structure

A tidal barrage is a dam-like structure used to capture the energy from masses of water moving in and out of a bay or river due to tidal forces.