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72-668: The Salmon Bay Bridge, which is located west of the Hiram M. Chittenden Locks , is the last bridge to span the Lake Washington Ship Canal before it becomes Puget Sound . Built in 1914 by the Great Northern Railway , it has an opening span of 61 meters (200 feet) and has two tracks. Additionally, vessel clearance when lowered is 13.1 meters (43 feet) at mean high tide, and up to 15.3 meters (50 feet) at low tide. BNSF Railway initially planned to replace

144-711: A sink or a source of carbon, depending on the specific wetland. If they function as a carbon sink, they can help with climate change mitigation . However, wetlands can also be a significant source of methane emissions due to anaerobic decomposition of soaked detritus , and some are also emitters of nitrous oxide . Humans are disturbing and damaging wetlands in many ways, including oil and gas extraction , building infrastructure, overgrazing of livestock , overfishing , alteration of wetlands including dredging and draining, nutrient pollution , and water pollution . Wetlands are more threatened by environmental degradation than any other ecosystem on Earth, according to

216-402: A frequency and duration to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally included swamps, marshes, bogs, and similar areas.' For each of these definitions and others, regardless of the purpose, hydrology is emphasized (shallow waters, water-logged soils). The soil characteristics and

288-436: A major run of Sockeye Salmon using stock from Baker River, Washington. The ladder was designed to use attraction water: fresh water flowing swiftly out the bottom of the fish ladder, in the direction opposite which anadromous fish migrate at the end of their lives. However, the attraction water from this first ladder was not effective. Instead, most salmon used the locks. This made them an easy target for predators like Herschel

360-455: A part of the rebuilding, the Corps also added an underground chamber with a viewing gallery. The fish approaching the ladder smell the attraction water, recognizing the scent of Lake Washington and its tributaries. They enter the ladder, and either jump over each of the 21 weirs or swim though tunnel-like openings. They exit the ladder into the fresh water of Salmon Bay. They continue following

432-410: A pipe discharging downstream of the locks area. In 1975, the saltwater drain was modified to divert some salt water from the basin to the fish ladder, where it is added via a diffuser to the fish ladder attraction water; see below . To further restrict saltwater intrusion, in 1966, a hinged barrier was installed just upstream of the large lock. This hollow metal barrier is filled with air to remain in

504-1259: A polar climate, wetland temperatures can be as low as −50 °C (−58 °F). Peatlands in arctic and subarctic regions insulate the permafrost , thus delaying or preventing its thawing during summer, as well as inducing its formation. The amount of precipitation a wetland receives varies widely according to its area. Wetlands in Wales , Scotland , and western Ireland typically receive about 1,500 mm (59 in) per year. In some places in Southeast Asia , where heavy rains occur, they can receive up to 10,000 mm (390 in). In some drier regions, wetlands exist where as little as 180 mm (7.1 in) precipitation occurs each year. Temporal variation: Surface flow may occur in some segments, with subsurface flow in other segments. Wetlands vary widely due to local and regional differences in topography , hydrology , vegetation , and other factors, including human involvement. Other important factors include fertility, natural disturbance, competition, herbivory , burial and salinity. When peat accumulates, bogs and fens arise. The most important factor producing wetlands

576-540: A portion of the overall water cycle, which also includes atmospheric water (precipitation) and groundwater . Many wetlands are directly linked to groundwater and they can be a crucial regulator of both the quantity and quality of water found below the ground. Wetlands that have permeable substrates like limestone or occur in areas with highly variable and fluctuating water tables have especially important roles in groundwater replenishment or water recharge. Substrates that are porous allow water to filter down through

648-422: A strong influence on wetland water chemistry, particularly in coastal wetlands and in arid and semiarid regions with large precipitation deficits. Natural salinity is regulated by interactions between ground and surface water, which may be influenced by human activity. Carbon is the major nutrient cycled within wetlands. Most nutrients, such as sulfur , phosphorus , carbon , and nitrogen are found within

720-489: A system of siphons and flushing mechanisms. Because the Cedar River was the main water source both for the lakes and locks and for Seattle's potable water, at times there were problems maintaining an adequate water supply to maintain lake level and operate the locks. Conversely, with several rivers redirected, flooding worsened throughout the watershed. That last problem was exacerbated by logging, and at times during storms

792-410: A unique kind of wetland where lush plant growth and slow decay of dead plants (under anoxic conditions) results in organic peat accumulating; bogs, fens, and mires are different names for peatlands. Variations of names for wetland systems: Some wetlands have localized names unique to a region such as the prairie potholes of North America's northern plain, pocosins , Carolina bays and baygalls of

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864-515: A wetland is "an ecosystem that arises when inundation by water produces soils dominated by anaerobic and aerobic processes, which, in turn, forces the biota, particularly rooted plants, to adapt to flooding". Sometimes a precise legal definition of a wetland is required. The definition used for regulation by the United States government is: 'The term "wetlands" means those areas that are inundated or saturated by surface or ground water at

936-422: A wetland system includes its plants ( flora ) and animals ( fauna ) and microbes (bacteria, fungi). The most important factor is the wetland's duration of flooding. Other important factors include fertility and salinity of the water or soils. The chemistry of water flowing into wetlands depends on the source of water, the geological material that it flows through and the nutrients discharged from organic matter in

1008-403: A wetland) affects hydro-periods (temporal fluctuations in water levels) by controlling the water balance and water storage within a wetland. Landscape characteristics control wetland hydrology and water chemistry. The O 2 and CO 2 concentrations of water depend upon temperature , atmospheric pressure and mixing with the air (from winds or water flows). Water chemistry within wetlands

1080-558: A whole. To replace these wetland ecosystem services , enormous amounts of money would need to be spent on water purification plants, dams, levees, and other hard infrastructure, and many of the services are impossible to replace. Floodplains and closed-depression wetlands can provide the functions of storage reservoirs and flood protection. The wetland system of floodplains is formed from major rivers downstream from their headwaters . "The floodplains of major rivers act as natural storage reservoirs, enabling excess water to spread out over

1152-594: A wide area, which reduces its depth and speed. Wetlands close to the headwaters of streams and rivers can slow down rainwater runoff and spring snowmelt so that it does not run straight off the land into water courses. This can help prevent sudden, damaging floods downstream." Notable river systems that produce wide floodplains include the Nile River , the Niger river inland delta, the Zambezi River flood plain,

1224-467: Is a stub . You can help Misplaced Pages by expanding it . Hiram M. Chittenden Locks The Hiram M. Chittenden Locks , or Ballard Locks , is a complex of locks at the west end of Salmon Bay in Seattle , Washington's Lake Washington Ship Canal , between the neighborhoods of Ballard to the north and Magnolia to the south. The Ballard Locks carry more boat traffic than any other lock in

1296-440: Is determined by the pH , salinity , nutrients, conductivity , soil composition, hardness , and the sources of water. Water chemistry varies across landscapes and climatic regions. Wetlands are generally minerotrophic (waters contain dissolved materials from soils) with the exception of ombrotrophic bogs that are fed only by water from precipitation. Because bogs receive most of their water from precipitation and humidity from

1368-412: Is hydrology, or flooding . The duration of flooding or prolonged soil saturation by groundwater determines whether the resulting wetland has aquatic, marsh or swamp vegetation . Other important factors include soil fertility, natural disturbance, competition, herbivory , burial, and salinity. When peat from dead plants accumulates, bogs and fens develop. Wetland hydrology is associated with

1440-619: Is integrated into the locks for migration of anadromous fish, notably salmon . The grounds feature a visitors center, as well as the Carl S. English Jr. Botanical Gardens . Operated by the US Army Corps of Engineers , the locks were formally opened on July 4, 1917, although the first ship passed on August 3, 1916. They were named after US Army Major Hiram M. Chittenden, the Seattle District Engineer for

1512-451: Is the only place in the world where both crocodiles and alligators coexist. The saltwater crocodile inhabits estuaries and mangroves. Snapping turtles also inhabit wetlands. Birds , particularly waterfowl and waders use wetlands extensively. Mammals of wetlands include numerous small and medium-sized species such as voles , bats , muskrats and platypus in addition to large herbivorous and apex predator species such as

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1584-459: Is tied down and ready for the chamber to be drained. Next, the upper gates ( A ) and the filling valve ( C ) are closed and the draining valve ( D ) is opened allowing water to drain via gravity out to Puget Sound. When the water pressure is equal on both sides of the gate, the lower gates ( B ) are opened, allowing the vessels to leave the lock chamber. The process is reversed for upstream locking. The complex includes two locks. Using

1656-545: Is usually saturated with water". More precisely, wetlands are areas where "water covers the soil , or is present either at or near the surface of the soil all year or for varying periods of time during the year, including during the growing season". A patch of land that develops pools of water after a rain storm would not necessarily be considered a "wetland", even though the land is wet. Wetlands have unique characteristics: they are generally distinguished from other water bodies or landforms based on their water level and on

1728-505: The Millennium Ecosystem Assessment from 2005. Methods exist for assessing wetland ecological health . These methods have contributed to wetland conservation by raising public awareness of the functions that wetlands can provide. Since 1971, work under an international treaty seeks to identify and protect " wetlands of international importance ." A simplified definition of wetland is "an area of land that

1800-688: The Pantanal in South America, and the Sundarbans in the Ganges - Brahmaputra delta. Wetlands contribute many ecosystem services that benefit people. These include for example water purification , stabilization of shorelines, storm protection and flood control . In addition, wetlands also process and condense carbon (in processes called carbon fixation and sequestration ), and other nutrients and water pollutants . Wetlands can act as

1872-444: The atmosphere , their water usually has low mineral ionic composition. In contrast, wetlands fed by groundwater or tides have a higher concentration of dissolved nutrients and minerals. Fen peatlands receive water both from precipitation and ground water in varying amounts so their water chemistry ranges from acidic with low levels of dissolved minerals to alkaline with high accumulation of calcium and magnesium . Salinity has

1944-576: The beavers , coypu , swamp rabbit , Florida panther , jaguar , and moose . Wetlands attract many mammals due to abundant seeds, berries, and other vegetation as food for herbivores, as well as abundant populations of invertebrates, small reptiles and amphibians as prey for predators. Invertebrates of wetlands include aquatic insects such as dragonflies , aquatic bugs and beetles , midges, mosquitos , crustaceans such as crabs, crayfish, shrimps, microcrustaceans, mollusks like clams, mussels, snails and worms. Invertebrates comprise more than half of

2016-497: The "peak" viewing time is during spawning season, from about the beginning of July through mid-August. A public art work, commissioned by the Seattle Arts Commission, provides literary interpretation of the experience through recordings of Seattle poet Judith Roche's "Salmon Suite," a sequence of five poems tied to the annual migratory sequence of the fish. Among the species of salmonids migrating routinely through

2088-787: The Black River and cutting off the Cedar River salmon run. The Cedar River was rerouted into Lake Washington to provide sufficient water flow for operating the Locks. Additionally the White River was rerouted into the Puyallup River. The Cedar and White Rivers both originally flowed into the Duwamish causing frequent flooding. The rerouting of the rivers opened up huge lowland areas for development but significantly disrupted

2160-491: The Corps of Engineers from April 1906 to September 1908. They were added to the National Register of Historic Places in 1978. Vessels passing from the freshwater Lakes Washington and Union to Puget Sound enter the lock chamber through the open upper gates ( A in the accompanying diagram). The lower gates ( B ) and the draining valve ( D ) are closed. The vessel is assisted by the lockwall attendants who assure it

2232-424: The Duwamish salmon runs. To rectify this problem, salmon runs were reintroduced allowing the fish to migrate through the locks. The locks officially opened for boat traffic on May 8, 1917. The total cost of the project to that point was $ 3.5 million, with $ 2.5 million having come from the federal government and the rest from local governments. To allow for the intended boat traffic, three bridges were removed along

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2304-635: The Locks but none have been seen in years. The run is considered functionally extinct. Wetland A wetland is a distinct semi-aquatic ecosystem whose groundcovers are flooded or saturated in water , either permanently, for years or decades, or only seasonally. Flooding results in oxygen -poor ( anoxic ) processes taking place, especially in the soils . Wetlands form a transitional zone between waterbodies and dry lands , and are different from other terrestrial or aquatic ecosystems due to their vegetation 's roots having adapted to oxygen-poor waterlogged soils . They are considered among

2376-419: The Locks gates were closed for the first time, turning Salmon Bay from saltwater to freshwater. The first ship passed through the locks on August 3, 1916. On August 25, 1916, the temporary dam at Montlake was breached. During the following three months, Lake Washington drained, lowering the water level by 8.8 ft (2.7 m) and drying up more than 1,000 acres (400 ha) of wetlands , as well as drying up

2448-639: The Okavango River inland delta, the Kafue River flood plain, the Lake Bangweulu flood plain (Africa), Mississippi River (US), Amazon River (South America), Yangtze River (China), Danube River (Central Europe) and Murray-Darling River (Australia). Groundwater replenishment can be achieved for example by marsh , swamp , and subterranean karst and cave hydrological systems. The surface water visibly seen in wetlands only represents

2520-481: The Salmon Bay Bridge with a new vertical-lift bridge , but chose to repair failing components of the existing bridge following consultation with the local community. In September 2022, the federal government issued a US$ 25 million dollar grant to fund mechanical upgrades, while BNSF contributed another $ 70 million dollars toward the effort. This article about a bridge in the U.S. state of Washington

2592-541: The South. White River was rerouted into the Puyallup River. Cedar and White Rivers did support significant Salmon runs but also created severe flooding conditions for the early settlers. The rerouting of these two major rivers was a mixed blessing, while reducing flood threats, the Duwamish River salmon runs were decimated. To rectify this situation, salmon runs were rerouted through the Locks, which included introducing

2664-522: The Southeastern US, mallines of Argentina, Mediterranean seasonal ponds of Europe and California, turloughs of Ireland, billabongs of Australia, among many others. Wetlands are found throughout the world in different climates. Temperatures vary greatly depending on the location of the wetland. Many of the world's wetlands are in the temperate zones , midway between the North or South Poles and

2736-453: The U.S., and the locks, along with the fish ladder and the surrounding Carl S. English Jr. Botanical Gardens , attract more than one million visitors annually, making it one of Seattle's top tourist attractions. The construction of the locks profoundly reshaped the topography of Seattle and the surrounding area, lowering the water level of Lake Washington and Lake Union by 8.8 feet (2.7 m), adding miles of new waterfront land, reversing

2808-793: The US Navy building the Puget Sound Naval Shipyard in Bremerton, Washington , which is located across the Sound from Seattle. In early 1909, the Washington State Legislature appropriated $ 250,000, placed under the control of the Corps of Engineers, for excavation of the canal between Lake Union and Lake Washington. In June 1910, the US Congress gave its approval for the lock, on the condition that

2880-502: The US, the best known classifications are the Cowardin classification system and the hydrogeomorphic (HGM) classification system. The Cowardin system includes five main types of wetlands: marine (ocean-associated), estuarine (mixed ocean- and river-associated), riverine (within river channels), lacustrine (lake-associated) and palustrine (inland nontidal habitats). Peatlands are

2952-610: The United States' commercial fish and shellfish stocks depend solely on estuaries to survive. Amphibians such as frogs and salamanders need both terrestrial and aquatic habitats in which to reproduce and feed. Because amphibians often inhabit depressional wetlands like prairie potholes and Carolina bays, the connectivity among these isolated wetlands is an important control of regional populations. While tadpoles feed on algae, adult frogs forage on insects. Frogs are sometimes used as an indicator of ecosystem health because their thin skin permits absorption of nutrients and toxins from

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3024-534: The dominant plants and the source of the water. For example, marshes are wetlands dominated by emergent herbaceous vegetation such as reeds , cattails and sedges . Swamps are dominated by woody vegetation such as trees and shrubs (although reed swamps in Europe are dominated by reeds, not trees). Mangrove forest are wetlands with mangroves , halophytic woody plants that have evolved to tolerate salty water . Examples of wetlands classified by

3096-418: The end of their life return to fresh water to spawn. Prior to the Locks construction, no significant salmon runs existed here, as there was only a small drainage stream from Lake Union into Salmon Bay. In order to provide enough water to operate the Locks, Cedar River was rerouted into Lake Washington (which was lowered 9 feet). Cedar River originally flowed into the Duwamish River along with the White River from

3168-634: The equator. In these zones, summers are warm and winters are cold, but temperatures are not extreme. In subtropical zone wetlands, such as along the Gulf of Mexico , average temperatures might be 11 °C (52 °F). Wetlands in the tropics are subjected to much higher temperatures for a large portion of the year. Temperatures for wetlands on the Arabian Peninsula can exceed 50 °C (122 °F) and these habitats would therefore be subject to rapid evaporation. In northeastern Siberia , which has

3240-532: The flow of rivers, and leaving piers in the eastern half of Salmon Bay high and dry. The Locks are listed on the National Register of Historic Places and have been designated by the American Society of Civil Engineers as a National Historic Civil Engineering Landmark . As early as 1854, there was discussion of building a navigable connection between Lake Washington and Puget Sound for

3312-504: The following areas: According to the Ramsar Convention: The economic worth of the ecosystem services provided to society by intact, naturally functioning wetlands is frequently much greater than the perceived benefits of converting them to 'more valuable' intensive land use – particularly as the profits from unsustainable use often go to relatively few individuals or corporations, rather than being shared by society as

3384-453: The freshwater levels of the ship canal and lakes. The gates on the dam release or store water to maintain the lake within a 2 ft (0.61 m) range of 20 to 22 ft (6.1 to 6.7 m) above sea level. Maintaining this lake level is necessary for floating bridges , mooring facilities, and vessel clearances under bridges. "Smolt flumes" in the spillway help young salmon to pass safely downstream. Higher water levels are maintained in

3456-468: The interface between truly terrestrial ecosystems and aquatic systems, making them inherently different from each other, yet highly dependent on both." In environmental decision-making, there are subsets of definitions that are agreed upon to make regulatory and policy decisions. Under the Ramsar international wetland conservation treaty , wetlands are defined as follows: An ecological definition of

3528-462: The known animal species in wetlands, and are considered the primary food web link between plants and higher animals (such as fish and birds). Depending on a wetland's geographic and topographic location, the functions it performs can support multiple ecosystem services , values, or benefits. United Nations Millennium Ecosystem Assessment and Ramsar Convention described wetlands as a whole to be of biosphere significance and societal importance in

3600-713: The ladder at the Chittenden Locks are Chinook (king) salmon ( Oncorhynchus tshawytscha ), Coho (silver) salmon ( Oncorhynchus kisutch ), Sockeye (red) salmon ( Oncorhynchus nerka ). Sockeye primarily migrate up the Cedar River to spawn and most end up at the Landsberg Dam Hatchery. Chinook and Coho migrate up the Issaquah Creek and most end up at the Issaquah Hatchery. Steelhead ( Oncorhynchus mykiss ), once migrated through

3672-501: The level of Puget Sound at a very low tide to the level of freshwater Salmon Bay, in 10–15 minutes. The locks handle both pleasure boats and commercial vessels, ranging from kayaks to fishing boats returning from the Bering Sea to cargo ships. Over 1 million tons of cargo, fuel, building materials, and seafood products pass through the locks each year. South of the small lock is a spillway dam with tainter gates used to regulate

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3744-488: The locks had to be opened just to allow water to flow out. The locks and associated facilities serve three purposes: The complex includes two locks, 30 ft × 150 ft (9.1 m × 45.7 m) (small) and 80 ft × 825 ft (24 m × 251 m) (large). The complex also includes a 235 ft (72 m) spillway with six 32 ft × 12 ft (9.8 m × 3.7 m) gates to assist in water-level control. A fish ladder

3816-406: The millions of young fish born, only a relative few survive to adulthood. Causes of death include natural predators, commercial and sport fishing, disease, low stream flows, poor water quality, flooding, and concentrated developments along streams and lakes. Visitors to the locks can observe the salmon through windows as they progress along their route. Although the viewing area is open year-round,

3888-438: The most biologically diverse of all ecosystems, serving as habitats to a wide range of aquatic and semi-aquatic plants and animals , with often improved water quality due to plant removal of excess nutrients such as nitrates and phosphorus . Wetlands exist on every continent , except Antarctica . The water in wetlands is either freshwater , brackish or saltwater . The main types of wetland are defined based on

3960-837: The plants and animals controlled by the wetland hydrology are often additional components of the definitions. Wetlands can be tidal (inundated by tides) or non-tidal. The water in wetlands is either freshwater , brackish , saline , or alkaline . There are four main kinds of wetlands – marsh , swamp , bog , and fen (bogs and fens being types of peatlands or mires ). Some experts also recognize wet meadows and aquatic ecosystems as additional wetland types. Sub-types include mangrove forests , carrs , pocosins , floodplains , peatlands, vernal pools , sinks , and many others. The following three groups are used within Australia to classify wetland by type: Marine and coastal zone wetlands, inland wetlands and human-made wetlands. In

4032-541: The purpose of transporting logs, milled lumber, and fishing vessels. Thirteen years later, the United States Navy endorsed a canal project, which included a plan for building a naval shipyard on Lake Washington. In 1891 the U.S. Army Corps of Engineers started planning the project. Some preliminary work was begun in 1906, and work began in earnest five years later under the command of Hiram M. Chittenden . The delays in canal planning and construction resulted in

4104-639: The rest of the canals along the route be paid for locally. Construction was then delayed by legal challenges, mainly by mill owners in Ballard who feared property damage and loss of waterfront in Salmon Bay, and by Lake Washington property owners. Under Major James. B. Cavanaugh , Chittenden's replacement as Seattle District Commander, construction of the Ballard, or Government, Locks connecting Salmon Bay to Shilshole Bay began in 1911, proceeding without further controversy or legal entanglements. In July 1912,

4176-418: The sea lion ; also, many were injured by hitting the walls and gates of the locks, or by hitting boat propellers. The Corps rebuilt the fish ladder in 1976 by increasing the flow of attraction water and adding more weirs : most weirs are now one foot higher than the previous one. The old fish ladder had only 10 "steps"; the new one has 21. A diffuser well mixes salt water gradually into the last 10 weirs. As

4248-602: The ship canal route, at Latona Avenue, Fremont, Stone Way. The Ballard and Fremont Bridges were completed in 1917, followed by the University Bridge in 1919, and Montlake Bridge in 1925. The University Bridge was improved in 1932, and in 1934 the Lake Washington Ship Canal project was declared complete. While generally a success, the project was not without its problems. Salt water began to make its way upstream toward Lake Union, requiring

4320-588: The small lock when boat traffic is low conserves fresh water during summer, when the lakes receive less inflow. Having two locks also allows one of the locks to be drained for maintenance without blocking all boat traffic. The large lock is drained for approximately 2-weeks, usually in November, and the small lock is drained for about the same period, usually in March. The locks can elevate a 760-by-80-foot (232 m × 24 m) vessel 26 ft (7.9 m), from

4392-429: The soil and underlying rock into aquifers which are the source of much of the world's drinking water . Wetlands can also act as recharge areas when the surrounding water table is low and as a discharge zone when it is high. Mangroves , coral reefs , salt marsh can help with shoreline stabilization and storm protection. Tidal and inter-tidal wetland systems protect and stabilize coastal zones. Coral reefs provide

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4464-537: The soil of wetlands. Anaerobic and aerobic respiration in the soil influences the nutrient cycling of carbon, hydrogen, oxygen, and nitrogen, and the solubility of phosphorus thus contributing to the chemical variations in its water. Wetlands with low pH and saline conductivity may reflect the presence of acid sulfates and wetlands with average salinity levels can be heavily influenced by calcium or magnesium. Biogeochemical processes in wetlands are determined by soils with low redox potential. The life forms of

4536-412: The soils and plants at higher elevations. Plants and animals may vary within a wetland seasonally or in response to flood regimes. There are four main groups of hydrophytes that are found in wetland systems throughout the world. Submerged wetland vegetation can grow in saline and fresh-water conditions. Some species have underwater flowers, while others have long stems to allow the flowers to reach

4608-530: The sources of water include tidal wetlands , where the water source is ocean tides ); estuaries , water source is mixed tidal and river waters; floodplains , water source is excess water from overflowed rivers or lakes; and bogs and vernal ponds , water source is rainfall or meltwater . The world's largest wetlands include the Amazon River basin , the West Siberian Plain ,

4680-406: The spatial and temporal dispersion, flow, and physio-chemical attributes of surface and ground waters. Sources of hydrological flows into wetlands are predominantly precipitation , surface water (saltwater or freshwater), and groundwater. Water flows out of wetlands by evapotranspiration , surface flows and tides , and subsurface water outflow. Hydrodynamics (the movement of water through and from

4752-406: The summer to accommodate recreation as well as to allow the lakes to act as a water storage basin in anticipation of drought conditions. If excessive salt water were allowed to migrate into Salmon Bay, the salt could eventually damage the freshwater ecosystem . To prevent this, a basin was dredged just above (east of) the large lock. The heavier salt water settles into the basin and drains through

4824-719: The surface of the water. When trees and shrubs comprise much of the plant cover in saturated soils, those areas in most cases are called swamps . The upland boundary of swamps is determined partly by water levels. This can be affected by dams Some swamps can be dominated by a single species, such as silver maple swamps around the Great Lakes . Others, like those of the Amazon basin , have large numbers of different tree species. Other examples include cypress ( Taxodium ) and mangrove swamps. Many species of fish are highly dependent on wetland ecosystems. Seventy-five percent of

4896-496: The surface. Submerged species provide a food source for native fauna, habitat for invertebrates, and also possess filtration capabilities. Examples include seagrasses and eelgrass . Floating water plants or floating vegetation are usually small, like those in the Lemnoideae subfamily (duckweeds). Emergent vegetation like the cattails ( Typha spp.), sedges ( Carex spp.) and arrow arum ( Peltandra virginica ) rise above

4968-464: The surrounding environment resulting in increased extinction rates in unfavorable and polluted environmental conditions. Reptiles such as snakes , lizards , turtles , alligators and crocodiles are common in wetlands of some regions. In freshwater wetlands of the Southeastern US, alligators are common and a freshwater species of crocodile occurs in South Florida. The Florida Everglades

5040-440: The types of plants that live within them. Specifically, wetlands are characterized as having a water table that stands at or near the land surface for a long enough period each year to support aquatic plants . A more concise definition is a community composed of hydric soil and hydrophytes . Wetlands have also been described as ecotones , providing a transition between dry land and water bodies. Wetlands exist "...at

5112-591: The upright position, blocking the heavier salt water. When necessary to accommodate deep-draft vessels, the barrier is flooded and sinks to the bottom of the chamber. The fish ladder at the Chittenden locks is unusual—materials published by the federal government say "unique"—in being located where salt and fresh water meet. Normally, fish ladders are located entirely within fresh water. Pacific salmon are anadromous ; they hatch in lakes, rivers, and streams—or, nowadays fish hatcheries —migrate to sea, and only at

5184-400: The waterway to the lake, river, or stream where they were born. Once there, the females lay eggs, which the males fertilize. Most salmon die shortly after spawning. The offspring remain in the fresh water until they are ready to migrate to the ocean as smolts . In a few years, the surviving adults return, climb the fish ladder, and reach their spawning ground to continue the life cycle. Of

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