Discharge (hydrology)

A floodplain or flood plain or bottomlands is an area of land adjacent to a river. Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high discharge. The soils usually consist of clays, silts, sands, and gravels deposited during floods.

Because of regular flooding, floodplains frequently have high soil fertility since nutrients are deposited with the flood waters. This can encourage farming; some important agricultural regions, such as the Nile and Mississippi river basins, heavily exploit floodplains. Agricultural and urban regions have developed near or on floodplains to take advantage of the rich soil and freshwater. However, the risk of inundation has led to increasing efforts to control flooding.

The St. Lawrence River (French: Fleuve Saint-Laurent, pronounced [flœv sɛ̃ lɔʁɑ̃]) is a large international river in the middle latitudes of North America connecting the Great Lakes to the North Atlantic Ocean. Its waters flow in a northeasterly direction from Lake Ontario to the Gulf of St. Lawrence, traversing Ontario and Quebec in Canada and New York in the United States. A section of the river demarcates the Canada–U.S. border.

As the primary drainage outflow of the Great Lakes Basin, the St. Lawrence has the second-highest discharge of any river in North America (after the Mississippi River) and the 16th-highest in the world. The estuary of the St. Lawrence is often cited by scientists as the largest in the world. Significant natural landmarks of the river and estuary include the 1,864 river islands of the Thousand Islands, the endangered whales of Saguenay–St. Lawrence Marine Park, and the limestone monoliths of the Mingan Archipelago.

Canals or artificial waterways are waterways or engineered channels built for drainage management (e.g. flood control and irrigation) or for conveyancing water transport vehicles (e.g. water taxi). They carry free, calm surface flow under atmospheric pressure, and can be thought of as artificial rivers.

In most cases, a canal has a series of dams and locks that create reservoirs of low speed current flow. These reservoirs are referred to as slack water levels, often just called levels. A canal can be called a navigation canal when it parallels a natural river and shares part of the latter's discharges and drainage basin, and leverages its resources by building dams and locks to increase and lengthen its stretches of slack water levels while staying in its valley.

The Volga (Russian: Волга, pronounced [ˈvoɫɡə] ) is the longest river in Europe and the longest endorheic basin river in the world. Situated in Russia, it flows through Central Russia to Southern Russia and into the Caspian Sea. The Volga has a length of 3,531 km (2,194 mi), and a catchment area of 1,360,000 km (530,000 sq mi). It is also Europe's largest river in terms of average discharge at delta – between 8,000 m/s (280,000 cu ft/s) and 8,500 m/s (300,000 cu ft/s) – and of drainage basin. It is widely regarded as the national river of Russia. The hypothetical old Russian state, the Rus' Khaganate, arose along the Volga c. 830 AD. Historically, the river served as an important meeting place of various Eurasian civilizations.

The river flows in Russia through forests, forest steppes and steppes. Five of the ten largest cities of Russia, including the nation's capital, Moscow, are located in the Volga's drainage basin. Because the Volga drains into the Caspian Sea, which is an endorheic body of water, the Volga does not naturally connect to any of the world's oceans.

In physics and engineering, in particular fluid dynamics, the volumetric flow rate (also known as volume flow rate, or volume velocity) is the volume of fluid which passes per unit time; usually it is represented by the symbol Q (sometimes ${\displaystyle {\dot {V}}}$). Its SI unit is cubic metres per second (m/s).

It contrasts with mass flow rate, which is the other main type of fluid flow rate. In most contexts a mention of "rate of fluid flow" is likely to refer to the volumetric rate. In hydrometry, the volumetric flow rate is known as discharge.

Streamflow, or channel runoff, is the flow of water in streams and other channels, and is a major element of the water cycle. It is one runoff component, the movement 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.

This article lists rivers by their average discharge measured in descending order of their water flow rate. Here, only those rivers whose discharge is more than 2,000 m/s (71,000 cu ft/s) are shown. It can be thought of as a list of the biggest rivers on Earth, measured by a specific metric.

For context, the volume of an Olympic-size swimming pool is 2,500 m (88,000 cu ft). The average flow rate at the mouth of the Amazon is sufficient to fill more than 83 such pools each second. The estimated global total for all rivers is 1.2 million m³/s (43 million cu ft/s), of which the Amazon would be approximately 18%.

The Po (/poʊ/ POH, Italian: [ˈpɔ]) is the longest river in Italy. It flows eastward across northern Italy, starting from the Cottian Alps. The river's length is 652 km (405 mi), or 682 km (424 mi) if the Maira, a right bank tributary, is included. The headwaters of the Po are formed by a spring seeping from a stony hillside at Pian del Re, a flat place at the head of the Val Po under the northwest face of Monviso. The Po then extends along the 45th parallel north before ending at a delta projecting into the Adriatic Sea near Venice.

Draining a basin of 74,000 km (29,000 sq mi), the Po is characterized by its large discharge (several rivers over 1,000 km have a discharge inferior or equal to the Po). It is, with the Rhône and Nile, one of the three Mediterranean rivers with the largest water discharge. As a result of its characteristics, the river is subject to heavy flooding. Consequently, over half its length is controlled with embankments.

The Orinoco (Spanish pronunciation: [oɾiˈnoko]) is one of the longest rivers in South America at 2,140 km (1,330 mi). Its drainage basin, sometimes known as the Orinoquia, covers approximately 1,000,000 km (390,000 sq mi), with 65% of it in Venezuela and 35% in Colombia. It is the fourth largest river in the world by discharge volume of water (39,000 m/s (1,400,000 cu ft/s) at delta) due to the high precipitation throughout its catchment area (2,300 millimetres per are [0.084 in/sq ft]). The Orinoco River and its tributaries are the major transportation system for eastern and interior Venezuela and the Llanos of Colombia. The environment and wildlife in the Orinoco's basin are extremely diverse.

A body of water, such as a river, canal or lake, is navigable if it is deep, wide and calm enough for a water vessel (e.g. boats) to pass safely. Navigability is also referred to in the broader context of a body of water having sufficient under keel clearance for a vessel.

Such a navigable water is called a waterway, and is preferably with few obstructions against direct traverse that need avoiding, such as rocks, reefs or trees. Bridges built over waterways must have sufficient clearance. High flow speed may make a channel unnavigable due to risk of ship collisions. Waters may be unnavigable because of ice, particularly in winter or high-latitude regions. Navigability also depends on context: a small river may be navigable by smaller craft such as a motorboat or a kayak, but unnavigable by a larger freighter or cruise ship. Shallow rivers may be made navigable by the installation of locks that regulate flow and increase upstream water level, or by dredging that deepens parts of the stream bed.

In hydrology, a current in a water body is the flow of water in any one particular direction. The current varies spatially as well as temporally, dependent upon the flow rate, stream gradient, and channel geometry. In tidal zones, the current and streams may reverse on the flood tide before resuming on the ebb tide. On a global scale, wind and the rotation of the earth greatly influence the flow of ocean currents.

In a stream or river the current is influenced by gravity; the term upstream (or upriver) refers to the direction towards the source of the stream (or river), i.e. against the direction of flow. Likewise, the term downstream or downriver describes the direction towards the mouth of the stream or river, in which the current flows. The terms left bank and right bank refer to the banks as seen from the direction of flow, in the downstream direction.

The Timok (Serbian and Bulgarian: Тимок, Romanian: Timoc), sometimes also known as Great Timok (Serbian: Велики Тимок / Veliki Timok, Romanian: Timocul Mare), is a river in eastern Serbia, a right tributary of the Danube. For the last 15 km of its run it forms a border between eastern Serbia and western Bulgaria.

It is a branchy system of many shorter rivers, many of them having the same name (Timok), only clarified with adjectives. From the farthest source in the system, that of the Svrljiški Timok, until its confluence (as Veliki Timok), the Timok is 202 km long. The area of the river basin is 4,626 km (1,786 sq mi). Its average discharge at the mouth is 31 m/s (1,100 cu ft/s). The Timok Valley is known for the most important Vlach population in Eastern Serbia.

The Bou Regreg (Arabic: أبو رقراق) is a river located in western Morocco which discharges into the Atlantic Ocean between the cities of Rabat and Salé. The estuary of this river is termed Wadi Sala.

The river is 240 kilometres long, with a tidal estuary of approximately 24 kilometres extending upriver. Its average discharge is 23 m/s and can reach 1500 m/s during periods of flooding. The source of the river originates from the Middle Atlas mountains at an altitude of 1627 meters on the level of Jbel Mtourzgane (province of Khemisset) and of Grou (province of Khénifra) and descends to its mouth at the Atlantic Ocean separating the cities of Rabat to the south and Salé to the north.