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97-625: The Kaiwharawhara Stream is a stream in the North Island of New Zealand – it flows through the northwestern part of New Zealand's capital, Wellington . Its headwaters lie within the suburb of Karori , and it passes through other suburbs and Otari-Wilton's Bush before reaching the western shore of Wellington Harbour in Kaiwharawhara near the terminal of the Interislander ferry. Part of its length runs roughly alongside

194-497: A 107 m (351 ft) tunnel was built as an air-raid shelter in 1944 and the stream was diverted through it after the war, to improve flood protection and allow for additional oil storage tanks. Fish in the stream include shortfinned eel , longfin eel (ōrea), giant kōkopu , kōaro , banded kōkopu , īnanga , shortjaw kōkopu , common bully (toitoi), giant bully (tītarakura), bluegill bully , redfin bully , goldfish , koi carp , perch and brown trout . About 20% of

291-439: A 6- or 7-fold increase in the flux of NO x to the atmosphere. Its production is a function of combustion temperature - the higher the temperature, the more NO x is produced. Fossil fuel combustion is a primary contributor, but so are biofuels and even the burning of hydrogen. However, the rate that hydrogen is directly injected into the combustion chambers of internal combustion engines can be controlled to prevent

388-403: A bed armor layer, and other depositional features, plus well defined banks due to bank erosion, are good identifiers when assessing for perennial streams. Particle size will help identify a perennial stream. Perennial streams cut through the soil profile, which removes fine and small particles. By assessing areas for relatively coarse material left behind in the stream bed and finer sediments along

485-658: A continuous aquatic habitat until they reach maturity. Crayfish and other crustaceans , snails , bivalves (clams), and aquatic worms also indicate the stream is perennial. These require a persistent aquatic environment for survival. Fish and amphibians are secondary indicators in assessment of a perennial stream because some fish and amphibians can inhabit areas without persistent water regime. When assessing for fish, all available habitat should be assessed: pools, riffles, root clumps and other obstructions. Fish will seek cover if alerted to human presence, but should be easily observed in perennial streams. Amphibians also indicate

582-470: A continuous or intermittent stream. The same non-perennial channel might change characteristics from intermittent to ephemeral over its course. Washes can fill up quickly during rains, and there may be a sudden torrent of water after a thunderstorm begins upstream, such as during monsoonal conditions. In the United States, an intermittent or seasonal stream is one that only flows for part of

679-615: A creek, especially one that is fed by a spring or seep . It is usually small and easily forded . A brook is characterised by its shallowness. A creek ( / k r iː k / ) or crick ( / k r ɪ k / ): In hydrography, gut is a small creek; this is seen in proper names in eastern North America from the Mid-Atlantic states (for instance, The Gut in Pennsylvania, Ash Gut in Delaware, and other streams) down into

776-422: A drainage network. Although each tributary has its own source, international practice is to take the source farthest from the river mouth as the source of the entire river system, from which the most extended length of the river measured as the starting point is taken as the length of the whole river system, and that furthest starting point is conventionally taken as the source of the whole river system. For example,

873-445: A few notable and well-known exceptions that include most Prochlorococcus and some Synechococcus that can only take up nitrogen as ammonium. The nutrients in the ocean are not uniformly distributed. Areas of upwelling provide supplies of nitrogen from below the euphotic zone. Coastal zones provide nitrogen from runoff and upwelling occurs readily along the coast. However, the rate at which nitrogen can be taken up by phytoplankton

970-533: A further build-up of fixed nitrogen in the ocean, with the potential consequence of eutrophication . Gray arrows represent an increase while black arrows represent a decrease in the associated process. As a result of extensive cultivation of legumes (particularly soy , alfalfa , and clover ), growing use of the Haber–Bosch process in the production of chemical fertilizers , and pollution emitted by vehicles and industrial plants, human beings have more than doubled

1067-540: A larger stream. Common terms for individual river distributaries in English-speaking countries are arm and channel . There are a number of regional names for a stream. A stream's source depends on the surrounding landscape and its function within larger river networks. While perennial and intermittent streams are typically supplied by smaller upstream waters and groundwater, headwater and ephemeral streams often derive most of their water from precipitation in

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1164-529: A major proportion of nitrogen conversion in the oceans . The stoichiometrically balanced formula for the ANAMMOX chemical reaction can be written as following, where an ammonium ion includes the ammonia molecule, its conjugated base : This an exergonic process (here also an exothermic reaction ) releasing energy, as indicated by the negative value of Δ G °, the difference in Gibbs free energy between

1261-404: A path into mines or other underground chambers. According to official U.S. definitions, the channels of intermittent streams are well-defined, as opposed to ephemeral streams, which may or may not have a defined channel, and rely mainly on storm runoff, as their aquatic bed is above the water table . An ephemeral stream does not have the biological, hydrological, and physical characteristics of

1358-412: A perennial stream and include tadpoles , frogs , salamanders , and newts . These amphibians can be found in stream channels, along stream banks, and even under rocks. Frogs and tadpoles usually inhabit shallow and slow moving waters near the sides of stream banks. Frogs will typically jump into water when alerted to human presence. Well defined river beds composed of riffles, pools, runs, gravel bars,

1455-483: A perennial stream, fine sediment may cling to riparian plant stems and tree trunks. Organic debris drift lines or piles may be found within the active overbank area after recent high flow. Streams, headwaters, and streams flowing only part of the year provide many benefits upstream and downstream. They defend against floods, remove contaminants, recycle nutrients that are potentially dangerous as well as provide food and habitat for many forms of fish. Such streams also play

1552-432: A plant or animal dies or an animal expels waste, the initial form of nitrogen is organic . Bacteria or fungi convert the organic nitrogen within the remains back into ammonium ( NH + 4 ), a process called ammonification or mineralization . Enzymes involved are: The conversion of ammonium to nitrate is performed primarily by soil-living bacteria and other nitrifying bacteria. In the primary stage of nitrification,

1649-472: A process that leads to high algal population and growth, especially blue-green algal populations. While not directly toxic to fish life, like ammonia, nitrate can have indirect effects on fish if it contributes to this eutrophication. Nitrogen has contributed to severe eutrophication problems in some water bodies. Since 2006, the application of nitrogen fertilizer has been increasingly controlled in Britain and

1746-406: A slow-moving wetted channel or stagnant area. This is evidence that iron-oxidizing bacteria are present, indicating persistent expression of oxygen-depleted ground water. In a forested area, leaf and needle litter in the stream channel is an additional indicator. Accumulation of leaf litter does not occur in perennial streams since such material is continuously flushed. In the adjacent overbank of

1843-486: A stream as intermittent, "showing interruptions in time or space". Generally, streams that flow only during and immediately after precipitation are termed ephemeral . There is no clear demarcation between surface runoff and an ephemeral stream, and some ephemeral streams can be classed as intermittent—flow all but disappearing in the normal course of seasons but ample flow (backups) restoring stream presence — such circumstances are documented when stream beds have opened up

1940-424: A stream is a critical factor in determining its character and is entirely determined by its base level of erosion. The base level of erosion is the point at which the stream either enters the ocean, a lake or pond, or enters a stretch in which it has a much lower gradient, and may be specifically applied to any particular stretch of a stream. In geological terms, the stream will erode down through its bed to achieve

2037-399: A symbiotic relationship with rhizobia, some nitrogen is assimilated in the form of ammonium ions directly from the nodules. It is now known that there is a more complex cycling of amino acids between Rhizobia bacteroids and plants. The plant provides amino acids to the bacteroids so ammonia assimilation is not required and the bacteroids pass amino acids (with the newly fixed nitrogen) back to

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2134-524: A thin layer called sheet wash, combined with a network of tiny rills, which together form the sheet runoff; when this water is focused in a channel, a stream is born. Some rivers and streams may begin from lakes or ponds. Freshwater's primary sources are precipitation and mountain snowmelt. However, rivers typically originate in the highlands, and are slowly created by the erosion of mountain snowmelt into lakes or rivers. Rivers usually flow from their source topographically, and erode as they pass until they reach

2231-627: A vital role in preserving our drinking water quality and supply, ensuring a steady flow of water to surface waters and helping to restore deep aquifers. The extent of land basin drained by a stream is termed its drainage basin (also known in North America as the watershed and, in British English, as a catchment). A basin may also be composed of smaller basins. For instance, the Continental Divide in North America divides

2328-449: Is Azotobacter . Symbiotic nitrogen-fixing bacteria such as Rhizobium usually live in the root nodules of legumes (such as peas, alfalfa, and locust trees). Here they form a mutualistic relationship with the plant, producing ammonia in exchange for carbohydrates . Because of this relationship, legumes will often increase the nitrogen content of nitrogen-poor soils. A few non-legumes can also form such symbioses . Today, about 30% of

2425-427: Is 1 mg/L. Dissolved Inorganic Nitrogen has a 5-year median of 1.01 mg/L, Ammoniacal Nitrogen , 0.006 mg/L, Nitrate Nitrogen , 1 mg/L, Dissolved Reactive Phosphorus , 0.0355 mg/L, Total Phosphorus, 0.048 mg/L, MCI , 96.6, QMCI 1.76, ASPM , 2.130, Taxonomic richness , 26, EPT richness 31%. Several tracks pass through the valley, including Te Araroa long distance trail, which uses

2522-435: Is a stream that branches off and flows away from a main stream channel, and the phenomenon is known as river bifurcation . Distributaries are common features of river deltas , and are often found where a valleyed stream enters wide flatlands or approaches the coastal plains around a lake or an ocean . They can also occur inland, on alluvial fans , or where a tributary stream bifurcates as it nears its confluence with

2619-518: Is also known as the ANAMMOX process, an abbreviation coined by joining the first syllables of each of these three words. This biological process is a redox comproportionation reaction, in which ammonia (the reducing agent giving electrons) and nitrite (the oxidizing agent accepting electrons) transfer three electrons and are converted into one molecule of diatomic nitrogen ( N 2 ) gas and two water molecules. This process makes up

2716-496: Is an anaerobic respiration process. Microbes which undertake DNRA oxidise organic matter and use nitrate as an electron acceptor, reducing it to nitrite , then ammonium ( NO − 3 → NO − 2 → NH + 4 ). Both denitrifying and nitrate ammonification bacteria will be competing for nitrate in the environment, although DNRA acts to conserve bioavailable nitrogen as soluble ammonium rather than producing dinitrogen gas. The AN aerobic AMM onia OX idation process

2813-432: Is an important component of the marine environment. One reason is that only continual input of new nitrogen can determine the total capacity of the ocean to produce a sustainable fish harvest. Harvesting fish from regenerated nitrogen areas will lead to a decrease in nitrogen and therefore a decrease in primary production. This will have a negative effect on the system. However, if fish are harvested from areas of new nitrogen

2910-458: Is an important process in the ocean as well. While the overall cycle is similar, there are different players and modes of transfer for nitrogen in the ocean. Nitrogen enters the water through the precipitation, runoff, or as N 2 from the atmosphere. Nitrogen cannot be utilized by phytoplankton as N 2 so it must undergo nitrogen fixation which is performed predominately by cyanobacteria . Without supplies of fixed nitrogen entering

3007-613: Is decreased in oligotrophic waters year-round and temperate water in the summer resulting in lower primary production. The distribution of the different forms of nitrogen varies throughout the oceans as well. Nitrate is depleted in near-surface water except in upwelling regions. Coastal upwelling regions usually have high nitrate and chlorophyll levels as a result of the increased production. However, there are regions of high surface nitrate but low chlorophyll that are referred to as HNLC (high nitrogen, low chlorophyll) regions. The best explanation for HNLC regions relates to iron scarcity in

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3104-484: Is likely to enhance nitrogen fixation by diazotrophs (gray arrow), which utilize H ions to convert nitrogen into bioavailable forms such as ammonia ( NH 3 ) and ammonium ions ( NH + 4 ). However, as pH decreases, and more ammonia is converted to ammonium ions (gray arrow), there is less oxidation of ammonia to nitrite (NO 2 ), resulting in an overall decrease in nitrification and denitrification (black arrows). This in turn would lead to

3201-425: Is present in the environment in a wide variety of chemical forms including organic nitrogen, ammonium ( NH + 4 ), nitrite ( NO − 2 ), nitrate ( NO − 3 ), nitrous oxide ( N 2 O ), nitric oxide (NO) or inorganic nitrogen gas ( N 2 ). Organic nitrogen may be in the form of a living organism, humus or in the intermediate products of organic matter decomposition. The processes in

3298-412: Is reduced to NO − 2 , N 2 O, N 2 , and NH + 4 depending on the conditions and microbial species involved. The fecal plumes of cetaceans also act as a junction in the marine nitrogen cycle, concentrating nitrogen in the epipelagic zones of ocean environments before its dispersion through various marine layers, ultimately enhancing oceanic primary productivity. The nitrogen cycle

3395-425: Is sometimes termed a "young" or "immature" stream, and the later state a "mature" or "old" stream. Meanders are looping changes of direction of a stream caused by the erosion and deposition of bank materials. These are typically serpentine in form. Typically, over time the meanders gradually migrate downstream. If some resistant material slows or stops the downstream movement of a meander, a stream may erode through

3492-441: Is toxic to plants. Due to their very high solubility and because soils are highly unable to retain anions , nitrates can enter groundwater . Elevated nitrate in groundwater is a concern for drinking water use because nitrate can interfere with blood-oxygen levels in infants and cause methemoglobinemia or blue-baby syndrome. Where groundwater recharges stream flow, nitrate-enriched groundwater can contribute to eutrophication ,

3589-456: Is usually called a creek and marked on topographic maps with a solid blue line. There are five generic classifications: "Macroinvertebrate" refers to easily seen invertebrates , larger than 0.5 mm, found in stream and river bottoms. Macroinvertebrates are larval stages of most aquatic insects and their presence is a good indicator that the stream is perennial. Larvae of caddisflies , mayflies , stoneflies , and damselflies require

3686-671: The Johnsonville Branch railway , a branch line that once formed part of the North Island Main Trunk Railway – the latter now passes over the stream near its mouth. Its main tributary is the Korimako Stream (which flows from Khandallah and Ngaio ), though it is also fed by other tributaries, and its catchment covers roughly 19 square kilometres (7.3 sq mi). Much of this area consists of parkland and other reserves, though

3783-691: The Tombigbee River basin. Continuing in this vein, a component of the Mississippi River basin is the Ohio River basin, which in turn includes the Kentucky River basin, and so forth. Stream crossings are where streams are crossed by roads , pipelines , railways , or any other thing which might restrict the flow of the stream in ordinary or flood conditions. Any structure over or in a stream which results in limitations on

3880-450: The nitrogenase enzyme that combines gaseous nitrogen with hydrogen to produce ammonia , which is converted by the bacteria into other organic compounds . Most biological nitrogen fixation occurs by the activity of molybdenum (Mo)-nitrogenase, found in a wide variety of bacteria and some Archaea . Mo-nitrogenase is a complex two-component enzyme that has multiple metal-containing prosthetic groups. An example of free-living bacteria

3977-441: The stratosphere , where it breaks down and acts as a catalyst in the destruction of atmospheric ozone . Nitrous oxide is also a greenhouse gas and is currently the third largest contributor to global warming , after carbon dioxide and methane . While not as abundant in the atmosphere as carbon dioxide, it is, for an equivalent mass, nearly 300 times more potent in its ability to warm the planet. Ammonia ( NH 3 ) in

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4074-480: The velocity of the stream. A perennial stream is one which flows continuously all year. Some perennial streams may only have continuous flow in segments of its stream bed year round during years of normal rainfall. Blue-line streams are perennial streams and are marked on topographic maps with a solid blue line. The word "perennial" from the 1640s, meaning "evergreen," is established in Latin perennis, keeping

4171-704: The Caribbean (for instance, Guinea Gut , Fish Bay Gut , Cob Gut , Battery Gut and other rivers and streams in the United States Virgin Islands , in Jamaica (Sandy Gut, Bens Gut River, White Gut River), and in many streams and creeks of the Dutch Caribbean ). A river is a large natural stream that is much wider and deeper than a creek and not easily fordable, and may be a navigable waterway . The linear channel between

4268-676: The Northern Walkway from Cummings Park via the Korimako valley and then a short length beside the Kaiwharawhara to Wadestown . The Sanctuary to Sea walkway uses most of the valley. Stream The flow of a stream is controlled by three inputs – surface runoff (from precipitation or meltwater ), daylighted subterranean water , and surfaced groundwater ( spring water ). The surface and subterranean water are highly variable between periods of rainfall. Groundwater, on

4365-436: The United States. This is occurring along the same lines as control of phosphorus fertilizer, restriction of which is normally considered essential to the recovery of eutrophied waterbodies. Denitrification is the reduction of nitrates back into nitrogen gas ( N 2 ), completing the nitrogen cycle. This process is performed by bacterial species such as Pseudomonas and Paracoccus , under anaerobic conditions. They use

4462-688: The aboveground physiology and growth of plants near large point sources of nitrogen pollution. Changes to plant species may also occur as nitrogen compound accumulation increases availability in a given ecosystem, eventually changing the species composition, plant diversity, and nitrogen cycling. Ammonia and ammonium – two reduced forms of nitrogen – can be detrimental over time due to increased toxicity toward sensitive species of plants, particularly those that are accustomed to using nitrate as their source of nitrogen, causing poor development of their roots and shoots. Increased nitrogen deposition also leads to soil acidification, which increases base cation leaching in

4559-514: The annual transfer of nitrogen into biologically available forms. In addition, humans have significantly contributed to the transfer of nitrogen trace gases from Earth to the atmosphere and from the land to aquatic systems. Human alterations to the global nitrogen cycle are most intense in developed countries and in Asia, where vehicle emissions and industrial agriculture are highest. Generation of Nr, reactive nitrogen , has increased over 10 fold in

4656-533: The atmosphere either by evaporation from soil and water bodies, or by plant evapotranspiration. By infiltration some of the water sinks into the earth and becomes groundwater, much of which eventually enters streams. Most precipitated water is partially bottled up by evaporation or freezing in snow fields and glaciers. The majority of the water flows as a runoff from the ground; the proportion of this varies depending on several factors, such as climate, temperature, vegetation, types of rock, and relief. This runoff begins as

4753-512: The atmosphere has tripled as the result of human activities. It is a reactant in the atmosphere, where it acts as an aerosol , decreasing air quality and clinging to water droplets, eventually resulting in nitric acid ( H NO 3 ) that produces acid rain . Atmospheric ammonia and nitric acid also damage respiratory systems. The very high temperature of lightning naturally produces small amounts of NO x , NH 3 , and HNO 3 , but high-temperature combustion has contributed to

4850-525: The base level of erosion throughout its course. If this base level is low, then the stream will rapidly cut through underlying strata and have a steep gradient, and if the base level is relatively high, then the stream will form a flood plain and meander. Typically, streams are said to have a particular elevation profile , beginning with steep gradients, no flood plain, and little shifting of channels, eventually evolving into streams with low gradients, wide flood plains, and extensive meanders. The initial stage

4947-597: The base stage of erosion. The scientists have offered a way based on data to define the origin of the lake. A classified sample was the one measured by the Chinese researchers from the University of Chinese Academy of Sciences. As an essential symbol of the river formation environment, the river source needs an objective and straightforward and effective method of judging . A calculation model of river source catchment area based on critical support flow (CSD) proposed, and

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5044-532: The catchment is predominantly in native vegetation, which includes karaka , parviflora var. arborea (koromiko-taranga), makomako , melicytus ramiflorus (mahoe), phormium tenax (harakeke) plagianthus regius (manatu), pohutukawa , pteridium esculentum (aruhe), rangiora , taupata , toetoe and veronica . Weeds in the valley include paraserianthes lophantha (brush wattle), cytisus scoparius (broom), fennel , gorse , pampas grass , rapeseed , tradescantia fluminensis and tree lupin . As noted above,

5141-466: The cycle. N 2 can be returned to the atmosphere through denitrification . Ammonium is thought to be the preferred source of fixed nitrogen for phytoplankton because its assimilation does not involve a redox reaction and therefore requires little energy. Nitrate requires a redox reaction for assimilation but is more abundant so most phytoplankton have adapted to have the enzymes necessary to undertake this reduction ( nitrate reductase ). There are

5238-503: The emission of NO x , an unintentional waste product. When those reactive nitrogens are released into the lower atmosphere, they can induce the formation of smog, particulate matter , and aerosols, all of which are major contributors to adverse health effects on human health from air pollution. In the atmosphere, NO 2 can be oxidized to nitric acid ( HNO 3 ), and it can further react with NH 3 to form ammonium nitrate ( NH 4 NO 3 ), which facilitates

5335-462: The euphotic zone is referred to as new nitrogen because it is newly arrived from outside the productive layer. The new nitrogen can come from below the euphotic zone or from outside sources. Outside sources are upwelling from deep water and nitrogen fixation. If the organic matter is eaten, respired, delivered to the water as ammonia, and re-incorporated into organic matter by phytoplankton it is considered recycled/regenerated production. New production

5432-467: The euphotic zone. Bacteria are able to convert ammonia to nitrite and nitrate but they are inhibited by light so this must occur below the euphotic zone. Ammonification or Mineralization is performed by bacteria to convert organic nitrogen to ammonia. Nitrification can then occur to convert the ammonium to nitrite and nitrate. Nitrate can be returned to the euphotic zone by vertical mixing and upwelling where it can be taken up by phytoplankton to continue

5529-444: The fact that nitrite and ammonium are intermediate species. They are both rapidly produced and consumed through the water column. The amount of ammonium in the ocean is about 3 orders of magnitude less than nitrate. Between ammonium, nitrite, and nitrate, nitrite has the fastest turnover rate. It can be produced during nitrate assimilation, nitrification, and denitrification; however, it is immediately consumed again. Nitrogen entering

5626-652: The flow is reduced to a trickle or less. Typically torrents have Apennine rather than Alpine sources, and in the summer they are fed by little precipitation and no melting snow. In this case the maximum discharge will be during the spring and autumn. An intermittent stream can also be called a winterbourne in Britain, a wadi in the Arabic -speaking world or torrente or rambla (this last one from arabic origin) in Spain and Latin America. In Australia, an intermittent stream

5723-447: The form of rain and snow. Most of this precipitated water re-enters the atmosphere by evaporation from soil and water bodies, or by the evapotranspiration of plants. Some of the water proceeds to sink into the earth by infiltration and becomes groundwater, much of which eventually enters streams. Some precipitated water is temporarily locked up in snow fields and glaciers , to be released later by evaporation or melting. The rest of

5820-458: The health of plants, animals, fish, and humans. Decreases in biodiversity can also result if higher nitrogen availability increases nitrogen-demanding grasses, causing a degradation of nitrogen-poor, species-diverse heathlands . Increasing levels of nitrogen deposition is shown to have several adverse effects on both terrestrial and aquatic ecosystems . Nitrogen gases and aerosols can be directly toxic to certain plant species, affecting

5917-487: The higher combustion temperatures that produce NO x . Ammonia and nitrous oxides actively alter atmospheric chemistry . They are precursors of tropospheric (lower atmosphere) ozone production, which contributes to smog and acid rain , damages plants and increases nitrogen inputs to ecosystems. Ecosystem processes can increase with nitrogen fertilization , but anthropogenic input can also result in nitrogen saturation, which weakens productivity and can damage

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6014-760: The human body, nitrate can react with organic compounds through nitrosation reactions in the stomach to form nitrosamines and nitrosamides , which are involved in some types of cancers (e.g., oral cancer and gastric cancer ). Human activities have also dramatically altered the global nitrogen cycle by producing nitrogenous gases associated with global atmospheric nitrogen pollution. There are multiple sources of atmospheric reactive nitrogen (Nr) fluxes. Agricultural sources of reactive nitrogen can produce atmospheric emission of ammonia ( NH 3 ), nitrogen oxides ( NO x ) and nitrous oxide ( N 2 O ). Combustion processes in energy production, transportation, and industry can also form new reactive nitrogen via

6111-407: The immediate vicinity of a stream is called a riparian zone . Given the status of the ongoing Holocene extinction , streams play an important corridor role in connecting fragmented habitats and thus in conserving biodiversity . The study of streams and waterways in general is known as surface hydrology and is a core element of environmental geography . A brook is a stream smaller than

6208-509: The impact of nitric acid rain deposition, resulting in the killing of fish and many other aquatic species. Ammonia ( NH 3 ) is highly toxic to fish, and the level of ammonia discharged from wastewater treatment facilities must be closely monitored. Nitrification via aeration before discharge is often desirable to prevent fish deaths. Land application can be an attractive alternative to aeration. Leakage of Nr (reactive nitrogen) from human activities can cause nitrate accumulation in

6305-532: The lake has significant feeder rivers. The Kagera River, which flows into Lake Victoria near Bukoba's Tanzanian town , is the longest feeder, though sources do not agree on which is the Kagera's longest tributary and therefore the Nile's most remote source itself. To qualify as a stream, a body of water must be either recurring or perennial. Recurring (intermittent) streams have water in the channel for at least part of

6402-683: The mainly easterly-draining Atlantic Ocean and Arctic Ocean basins from the largely westerly-flowing Pacific Ocean basin. The Atlantic Ocean basin, however, may be further subdivided into the Atlantic Ocean and Gulf of Mexico drainages. (This delineation is termed the Eastern Continental Divide .) Similarly, the Gulf of Mexico basin may be divided into the Mississippi River basin and several smaller basins, such as

6499-532: The marine cycle, the fixed nitrogen would be used up in about 2000 years. Phytoplankton need nitrogen in biologically available forms for the initial synthesis of organic matter. Ammonia and urea are released into the water by excretion from plankton. Nitrogen sources are removed from the euphotic zone by the downward movement of the organic matter. This can occur from sinking of phytoplankton, vertical mixing, or sinking of waste of vertical migrators. The sinking results in ammonia being introduced at lower depths below

6596-412: The meaning as "everlasting all year round," per "over" plus annus "year." This has been proved since the 1670s by the "living years" in the sense of botany. The metaphorical sense of "enduring, eternal" originates from 1750. They are related to "perennial." See biennial for shifts in vowels. Perennial streams have one or more of these characteristics: Absence of such characteristics supports classifying

6693-459: The movement of fish or other ecological elements may be an issue. Nitrogen cycle#Consequence of human modification of the nitrogen cycle The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmospheric , terrestrial , and marine ecosystems . The conversion of nitrogen can be carried out through both biological and physical processes. Important processes in

6790-567: The natural water environment, which can create harmful impacts on human health. Excessive use of N-fertilizer in agriculture has been a significant source of nitrate pollution in groundwater and surface water. Due to its high solubility and low retention by soil, nitrate can easily escape from the subsoil layer to the groundwater, causing nitrate pollution. Some other non-point sources for nitrate pollution in groundwater originate from livestock feeding, animal and human contamination, and municipal and industrial waste. Since groundwater often serves as

6887-453: The neck between two legs of a meander to become temporarily straighter, leaving behind an arc-shaped body of water termed an oxbow lake or bayou . A flood may also cause a meander to be cut through in this way. The stream load is defined as the solid matter carried by a stream. Streams can carry sediment, or alluvium. The amount of load it can carry (capacity) as well as the largest object it can carry (competence) are both dependent on

6984-605: The nitrate as an electron acceptor in the place of oxygen during respiration. These facultatively (meaning optionally) anaerobic bacteria can also live in aerobic conditions. Denitrification happens in anaerobic conditions e.g. waterlogged soils. The denitrifying bacteria use nitrates in the soil to carry out respiration and consequently produce nitrogen gas, which is inert and unavailable to plants. Denitrification occurs in free-living microorganisms as well as obligate symbionts of anaerobic ciliates. Dissimilatory nitrate reduction to ammonium (DNRA), or nitrate/nitrite ammonification,

7081-462: The nitrogen cycle include fixation , ammonification , nitrification , and denitrification . The majority of Earth's atmosphere (78%) is atmospheric nitrogen , making it the largest source of nitrogen. However, atmospheric nitrogen has limited availability for biological use, leading to a scarcity of usable nitrogen in many types of ecosystems . The nitrogen cycle is of particular interest to ecologists because nitrogen availability can affect

7178-426: The nitrogen cycle is to transform nitrogen from one form to another. Many of those processes are carried out by microbes , either in their effort to harvest energy or to accumulate nitrogen in a form needed for their growth. For example, the nitrogenous wastes in animal urine are broken down by nitrifying bacteria in the soil to be used by plants. The diagram alongside shows how these processes fit together to form

7275-459: The nitrogen cycle. The conversion of nitrogen gas ( N 2 ) into nitrates and nitrites through atmospheric, industrial and biological processes is called nitrogen fixation. Atmospheric nitrogen must be processed, or " fixed ", into a usable form to be taken up by plants. Between 5 and 10 billion kg per year are fixed by lightning strikes, but most fixation is done by free-living or symbiotic bacteria known as diazotrophs . These bacteria have

7372-433: The nitrogen will be replenished. As illustrated by the diagram on the right, additional carbon dioxide (CO 2 ) is absorbed by the ocean and reacts with water, carbonic acid ( H 2 CO 3 ) is formed and broken down into both bicarbonate ( HCO − 3 ) and hydrogen ( H ) ions (gray arrow), which reduces bioavailable carbonate ( CO 2− 3 ) and decreases ocean pH (black arrow). This

7469-487: The ocean, which may play an important part in ocean dynamics and nutrient cycles. The input of iron varies by region and is delivered to the ocean by dust (from dust storms ) and leached out of rocks. Iron is under consideration as the true limiting element to ecosystem productivity in the ocean. Ammonium and nitrite show a maximum concentration at 50–80 m (lower end of the euphotic zone ) with decreasing concentration below that depth. This distribution can be accounted for by

7566-596: The origin of the Nile River is the confluence of the White Nile and the Blue Nile, but the source of the whole river system is in its upper reaches. If there is no specific designation, "length of the Nile" refers to the "river length of the Nile system", rather than to the length of the Nile river from the point where it is formed by a confluence of tributaries. The Nile's source is often cited as Lake Victoria, but

7663-430: The other hand, has a relatively constant input and is controlled more by long-term patterns of precipitation. The stream encompasses surface, subsurface and groundwater fluxes that respond to geological, geomorphological, hydrological and biotic controls. Streams are important as conduits in the water cycle , instruments in groundwater recharge , and corridors for fish and wildlife migration. The biological habitat in

7760-489: The oxidation of ammonium ( NH + 4 ) is performed by bacteria such as the Nitrosomonas species, which converts ammonia to nitrites ( NO − 2 ). Other bacterial species such as Nitrobacter , are responsible for the oxidation of the nitrites ( NO − 2 ) into nitrates ( NO − 3 ). It is important for the ammonia ( NH 3 ) to be converted to nitrates or nitrites because ammonia gas

7857-415: The parallel ridges or bars on a shoreline beach or river floodplain, or between a bar and the shore. Also called a swale . A tributary is a contributory stream to a larger stream, or a stream which does not reach a static body of water such as a lake , bay or ocean but joins another river (a parent river). Sometimes also called a branch or fork. A distributary , or a distributary channel ,

7954-453: The past century due to global industrialisation . This form of nitrogen follows a cascade through the biosphere via a variety of mechanisms, and is accumulating as the rate of its generation is greater than the rate of denitrification . Nitrous oxide ( N 2 O ) has risen in the atmosphere as a result of agricultural fertilization, biomass burning, cattle and feedlots, and industrial sources. N 2 O has deleterious effects in

8051-422: The plant, thus forming an interdependent relationship. While many animals, fungi, and other heterotrophic organisms obtain nitrogen by ingestion of amino acids , nucleotides , and other small organic molecules, other heterotrophs (including many bacteria ) are able to utilize inorganic compounds, such as ammonium as sole N sources. Utilization of various N sources is carefully regulated in all organisms. When

8148-427: The primary domestic water supply, nitrate pollution can be extended from groundwater to surface and drinking water during potable water production, especially for small community water supplies, where poorly regulated and unsanitary waters are used. The WHO standard for drinking water is 50 mg NO − 3 L for short-term exposure, and for 3 mg NO − 3 L chronic effects. Once it enters

8245-419: The products of reaction and the reagents. Though nitrogen fixation is the primary source of plant-available nitrogen in most ecosystems , in areas with nitrogen-rich bedrock , the breakdown of this rock also serves as a nitrogen source. Nitrate reduction is also part of the iron cycle , under anoxic conditions Fe(II) can donate an electron to NO − 3 and is oxidized to Fe(III) while NO − 3

8342-410: The rate of key ecosystem processes, including primary production and decomposition . Human activities such as fossil fuel combustion, use of artificial nitrogen fertilizers, and release of nitrogen in wastewater have dramatically altered the global nitrogen cycle . Human modification of the global nitrogen cycle can negatively affect the natural environment system and also human health. Nitrogen

8439-469: The relationship between CSA and CSD with a minimum catchment area established. Using the model for comparison in two basins in Tibet (Helongqu and Niyang River White Water), the results show that the critical support flow (Qc) of the housing dragon song is 0.0028 m /s. At the same time, the white water curvature is 0.0085 m /s. Besides, the critical support flow can vary with hydrologic climate conditions, and

8536-425: The side of the stream or within the floodplain will be a good indicator of persistent water regime. A perennial stream can be identified 48 hours after a storm. Direct storm runoff usually has ceased at this point. If a stream is still flowing and contributing inflow is not observed above the channel, the observed water is likely baseflow. Another perennial stream indication is an abundance of red rust material in

8633-748: The soil and amounts of aluminum and other potentially toxic metals, along with decreasing the amount of nitrification occurring and increasing plant-derived litter. Due to the ongoing changes caused by high nitrogen deposition, an environment's susceptibility to ecological stress and disturbance – such as pests and pathogens – may increase, thus making it less resilient to situations that otherwise would have little impact on its long-term vitality. Additional risks posed by increased availability of inorganic nitrogen in aquatic ecosystems include water acidification; eutrophication of fresh and saltwater systems; and toxicity issues for animals, including humans. Eutrophication often leads to lower dissolved oxygen levels in

8730-471: The stream passes through a disused landfill and has other pollution sources. The stream mouth has lead and zinc pollution. It is in the worst 25% of all sites across the country for E. coli and very likely degrading. A 5-year median for clarity is 3.34 m (11.0 ft) and likely improving. Similarly turbidity 5-year median is 1.26 NTU and improving, as is Total Nitrogen with a 5-year median of 1.2 mg/L. The 5-year median of Total Oxidised Nitrogen

8827-519: The total fixed nitrogen is produced industrially using the Haber-Bosch process, which uses high temperatures and pressures to convert nitrogen gas and a hydrogen source (natural gas or petroleum) into ammonia. Plants can absorb nitrate or ammonium from the soil by their root hairs. If nitrate is absorbed, it is first reduced to nitrite ions and then ammonium ions for incorporation into amino acids, nucleic acids, and chlorophyll. In plants that have

8924-655: The vital support flow Qc in wet areas (white water) is larger than in semi-arid regions (heap slot). The proposed critical support flow (CSD) concept and model method can be used to determine the hydrographic indicators of river sources in complex geographical areas, and it can also reflect the impact of hydrologic climate change on river recharge in different regions. The source of a river or stream (its point of origin) can consist of lakes, swamps, springs, or glaciers. A typical river has several tributaries; each of these may be made up of several other smaller tributaries, so that together this stream and all its tributaries are called

9021-635: The water column, including hypoxic and anoxic conditions, which can cause death of aquatic fauna. Relatively sessile benthos, or bottom-dwelling creatures, are particularly vulnerable because of their lack of mobility, though large fish kills are not uncommon. Oceanic dead zones near the mouth of the Mississippi in the Gulf of Mexico are a well-known example of algal bloom -induced hypoxia . The New York Adirondack Lakes , Catskills , Hudson Highlands , Rensselaer Plateau and parts of Long Island display

9118-512: The water flows off the land as runoff, the proportion of which varies according to many factors, such as wind, humidity, vegetation, rock types, and relief. This runoff starts as a thin film called sheet wash, combined with a network of tiny rills, together constituting sheet runoff; when this water is concentrated in a channel, a stream has its birth. Some creeks may start from ponds or lakes. The streams typically derive most of their water from rain and snow precipitation. Most of this water re-enters

9215-499: The water suffers from pollution in the form of stormwater and runoff associated with urban land-use. The Kaiwharawhara name is from kai, the Māori word for food, and wharawhara, the edible fruit of Astelia Banksii . It is piped along six sections, the main length being 846 m (2,776 ft), under the former landfill at Ian Galloway Park , from Zealandia (wildlife sanctuary) to Otari-Wilton's Bush . Near its mouth at Kaiwharawhara,

9312-521: The year and is marked on topographic maps with a line of blue dashes and dots. A wash , desert wash, or arroyo is normally a dry streambed in the deserts of the American Southwest , which flows after sufficient rainfall. In Italy, an intermittent stream is termed a torrent ( Italian : torrente ). In full flood the stream may or may not be "torrential" in the dramatic sense of the word, but there will be one or more seasons in which

9409-402: The year. A stream of the first order is a stream which does not have any other recurring or perennial stream feeding into it. When two first-order streams come together, they form a second-order stream. When two second-order streams come together, they form a third-order stream. Streams of lower order joining a higher order stream do not change the order of the higher stream. The gradient of

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