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56-463: Hāmūn is a generic term which refers to shallow lakes (or lagoons), usually seasonal, that occur in the deserts of southeast Iran and adjacent areas of Afghanistan and Pakistan as a product of snowmelt in nearby mountains in spring. The term Hāmūn Lake (or Lake Hāmūn) equally applies to Hāmūn-e Helmand (entirely in Iran), as well to the shallow lakes Hāmūn-e Sabari and Hāmūn-e Puzak, which extend into

112-711: 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

168-402: 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

224-1259: 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

280-540: 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

336-445: A standstill, which has resulted in the abandonment of many villages as people migrate in search of water. Combination of drought and the massive irrigation proved to be a shock to the wetlands . Within five years period (1998-2002) once fertile wetlands rapidly deteriorated. We could reasonably presume that transformation of Hamoun into arid country, like their surrounding areas, was mainly caused by irrigated agriculture expansion since

392-422: 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

448-410: 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

504-552: A wasteland. Winds that were once cooled by the waters of the wetlands now drifting dust, sand, and salt from the dried lakebeds onto the surrounding villages, and these sand drifts have submerged nearly 100 villages beneath dunes in a landscape reminiscent of the Aral Sea disaster. Most of the crops have been reduced to dust bowl conditions, livestock herds have been decimated, and thriving fishery with an annual catch of around 12,000 tons has been wiped out. Many who had lived around

560-515: 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

616-422: 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

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672-403: 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

728-558: 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

784-594: 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,

840-440: 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

896-489: Is drawn down by other natural or human-induced reasons, the result is a dry lake bed in Iran. In addition, when the lake is dry, seasonal winds blow fine sands off the exposed lake bed. The sand is swirled into huge dunes that may cover a hundred or more fishing villages along the former lakeshore. Wildlife around the lake is negatively impacted and fisheries are brought to a halt. Changes in water policies and substantial rains in

952-633: Is either freshwater , brackish or saltwater . The main types of wetland are defined based on 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

1008-412: 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

1064-568: Is located about 35km southwest of Dahan-e Gholaman. In 1975 the Hāmūn-e Helmand , together with Hāmūn-e Sabari , was designated a Ramsar site . In the past five millennia, people have lived around Hamoun Oasis and its wetlands and their wildlife. Specific culture formed around the Hamoun with a way of life suited to the desert wetlands. They fashioned long reed boats to navigate the shallow waters and erected squat, red clay houses to withstand

1120-687: Is located in Afghanistan on the Sīstān marshes west of the Dasht-e Mārgō desert where the Helmand River forms a dendritic delta . Water flows in a circular fashion through a string of lakes starting with Hāmūn-e Puzak in the northeast, sweeping into Hāmūn-e Sabari and finally overflows into Hāmūn-e Helmand in the southwest. It used to cover an area of about 4,000 km (1,500 sq mi) with dense reed beds and tamarisk thicket fringing on

1176-451: 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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1232-545: 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

1288-497: The Farah Province of Afghanistan. The Harut River flows into the lake on the Afghanistan side of the border. In 1976, when rivers in Afghanistan were flowing regularly, the amount of water in the lake was relatively high. Between 1999 and 2001, however, the lake all but dried up and disappeared, as can be seen in the 2001 satellite image. When droughts occur in Afghanistan, or the water in watersheds that support Lake Hāmūn

1344-505: 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

1400-688: 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

1456-662: The Sīstān flatlands. Hamun Lake is sometimes categorized as three sibling shallow lakes, that is, Hamun-e Helmand, Hāmūn-e Sabari and Hāmūn-e Puzak , the latter extending into the Lash Wa Juwayn District of Farah Province in Afghanistan. Lake Hāmūn is fed primarily by water catchments on the Afghan side, including the Harut River . It is in the Sistan region and it is in the Lash Wa Juwayn District of

1512-444: 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

1568-576: 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

1624-607: 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 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

1680-464: The 1970s (represent as bright red patches on satellite images, mainly wheat and barley), coupled with one of the worst droughts ever witnessed in Central Asia in 1999-2001 period. The wetlands have been replaced mostly by lifeless salt flats and decaying reed stands . The wildlife, the towns, the fisheries, and the agriculture that once surrounded the Hamoun have all fallen away, giving rise to

1736-627: The Hamoun for generations either moved away or lost everything. Local bird population disappeared and migratory birds no longer stop for lack of refuge, and wildlife that could not sustain themselves in the desert or make the long journey to another oasis died. The rest of the wetlands now give off the harsh glare of dried salt flats . The only relatively large bodies of standing water are Chāh-Nīmeh IV reservoir maintained for drinking water. Hamun A hamun (or hamoun) ( Persian : هامون hāmūn ) refers to inland desert lakes or marshlands, formed as natural seasonal reservoirs in areas adjoining

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1792-656: The Helmand basin, found across eastern Iran , southern Afghanistan and western Pakistan . They form a critical link in the wildlife of the area, aquatic as well as avian and terrestrial. The better-known hamuns include: This Asia location article is a stub . You can help Misplaced Pages by expanding it . 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

1848-639: 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

1904-522: 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

1960-502: 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

2016-610: 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

2072-514: The basin. Farther west, revolving Afghan governments constructed large dams (Arghandab Dam, Kajaki Dam ) that diverted water from the upper reaches of the river. Precipitation variability in the Hindu Kush results in alternating periods of flooding in the Helmand and droughts, which may cause entire lagoons to dry up. This occurred several times in the 20th century when only the uppermost of

2128-429: The edges of the upper lakes. The area was thriving with wildlife animals and migratory birds. A trapezoid-shaped basalt outcropping, known as Mount Khajeh , rises up as an island in the middle of which used to be Hāmūn Lake and the northeastern edge of Hāmūn-e Helmand . Its flat-topped peak rises up 609 meters above sea level with a diameter of 2–2.5 km (1.2–1.6 mi), being the only remaining natural uplift in

2184-634: 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

2240-504: 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

2296-454: The heat of the desert. Their livelihood was based almost entirely on hunting, fishing, and farming. Until the late 20th century, irrigation waxed and waned in the Sīstān Basin for over 4,000 years without destroying the wetlands, but then population rapidly increased and new water management technologies were brought to the region. Soon irrigation schemes began to snake their way throughout

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2352-468: 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

2408-462: 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

2464-616: The lakes remained flooded. Landsat satellite imagery show how dramatic decrease in precipitation resulted in decrease of snow-covered area in the Helmand Basin, from 41,000 km in 1998 to 26,000 km in 2000. By 2001, Iran and Afghanistan were experienced for the third consecutive year an extreme drought that was so severe that the Hamoun dried out completely. Sīstān 's population, swelled by refugees from war-torn Afghanistan, has been severely affected by water shortages. Irrigation channels have run dry and agriculture has come to

2520-837: 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

2576-570: The region hope to effect a return of much of the water in Lake Hamoun by 2003. In 1975 the Hāmūn, together with Hāmūn-e Sabari , was designated a Ramsar site . The area has important archeological remains. The giant prehistoric city of Shahr-e Sukhteh is located in the area. Also the ruins of an ancient Achaemenid city Dahan-e Gholaman (“Gate of Slaves”) are near the Hāmūn Lake. Shahr-i-Sokhta

2632-429: 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

2688-537: 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

2744-412: 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

2800-530: 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 ,

2856-406: 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

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2912-719: 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

2968-496: 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

3024-464: 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

3080-419: The territory of present-day Afghanistan with the latter almost entirely inside Afghanistan. The Hamun is fed by numerous seasonal water tributaries; the main tributary is the perennial Helmand River , which originates in the Hindu Kush mountains in Afghanistan. In modern times, and prior to the existence of the dams for agricultural irrigation, spring floods would bring into existence much larger lakes. It

3136-440: 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

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