The Natimuk-Douglas Wetlands comprise a chain of freshwater and saline wetlands in the semi-arid Wimmera region of western Victoria. Australia, they are important for waterbirds. The wetlands lie between the small towns of Goroke on the west and Natimuk on the east, while the Little Desert National Park lies to the north and the Grampians National Park to the south-east; the Wimmera experiences mild, wet winters. Most of the wetlands are ephemeral and subject to seasonal flooding, but some retain water throughout the year. Many of the wetlands are fringed by saltmarsh. Most of the wetlands have some protection in small, individual reserves surrounded by farmland, though seasonal waterfowl hunting is permitted on many; the area has been identified by BirdLife International as a fragmented 65 km2 Important Bird Area because it has supported over 1% of the world populations of Australian shelducks, banded stilts, red-necked avocets and red-capped plovers. Other waterbirds sometimes using the site in moderate numbers include musk ducks, black swans, grey teals, hoary-headed grebes and sharp-tailed sandpipers.
The saltmarsh provides foraging habitat for blue-winged parrots. Red-tailed black cockatoos, flame robins and diamond firetails are seen
A wetland is a distinct ecosystem, inundated by water, either permanently or seasonally, where oxygen-free processes prevail. The primary factor that distinguishes wetlands from other land forms or water bodies is the characteristic vegetation of aquatic plants, adapted to the unique hydric soil. Wetlands play a number of functions, including water purification, water storage, processing of carbon and other nutrients, stabilization of shorelines, support of plants and animals. Wetlands are considered the most biologically diverse of all ecosystems, serving as home to a wide range of plant and animal life. Whether any individual wetland performs these functions, the degree to which it performs them, depends on characteristics of that wetland and the lands and waters near it. Methods for assessing these functions, wetland ecological health, general wetland condition have been developed in many regions and have contributed to wetland conservation by raising public awareness of the functions and the ecosystem services some wetlands provide.
Wetlands occur on every continent. The main wetland types are swamp, marsh and fen. Many peatlands are wetlands; the water in wetlands is either brackish, or saltwater. Wetlands can be non-tidal; the largest wetlands include the Amazon River basin, the West Siberian Plain, the Pantanal in South America, the Sundarbans in the Ganges-Brahmaputra delta. The UN Millennium Ecosystem Assessment determined that environmental degradation is more prominent within wetland systems than any other ecosystem on Earth. Constructed wetlands are used to treat municipal and industrial wastewater as well as stormwater runoff, they may play a role in water-sensitive urban design. A patch of land that develops pools of water after a rain storm would not be considered a "wetland" though the land is wet. Wetlands have unique characteristics: they are distinguished from other water bodies or landforms based on their water level and on the types of plants that live within them. 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 been described as ecotones, providing a transition between dry land and water bodies. Mitsch and Gosselink write that wetlands exist "...at the interface between terrestrial ecosystems and aquatic systems, making them inherently different from each other, yet dependent on both."In environmental decision-making, there are subsets of definitions that are agreed upon to make regulatory and policy decisions. 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 rooted plants, to adapt to flooding." There are four main kinds of wetlands – marsh, swamp and fen. Some experts recognize wet meadows and aquatic ecosystems as additional wetland types; the largest wetlands in the world include the swamp forests of the Amazon and the peatlands of Siberia. Under the Ramsar international wetland conservation treaty, wetlands are defined as follows: Article 1.1: "...wetlands are areas of marsh, peatland or water, whether natural or artificial, permanent or temporary, with water, static or flowing, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres."
Article 2.1: " may incorporate riparian and coastal zones adjacent to the wetlands, islands or bodies of marine water deeper than six metres at low tide lying within the wetlands." Although the general definition given above applies around the world, each county and region tends to have its own definition for legal purposes. In the United States, wetlands are defined as "those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, that under normal circumstances do support, a prevalence of vegetation adapted for life in saturated soil conditions. Wetlands include swamps, marshes and similar areas"; this definition has been used in the enforcement of the Clean Water Act. Some US states, such as Massachusetts and New York, have separate definitions that may differ from the federal government's. In the United States Code, the term wetland is defined "as land that has a predominance of hydric soils, is inundated or saturated by surface or groundwater at a frequency and duration sufficient to support a prevalence of hydrophytic vegetation adapted for life in saturated soil conditions and under normal circumstances supports a prevalence of such vegetation."
Related to this legal definitions, the term "normal circumstances" are conditions expected to occur during the wet portion of the growing season under normal climatic conditions, in the absence of significant disturbance. It is not uncommon for a wetland to be dry for long portions of the growing season. Wetlands can be dry during the dry season and abnormally dry periods during the wet season, but under normal environmental conditions the soils in a wetland will be saturated to the surface or inundated such that the soils become anaerobic, those conditions will persist through the wet portion of the growing season; the most important factor producing wetlands is flooding. The duration of flooding or prolonged soil saturation by groundwater determines whether the resulting wetland has aquatic, marsh or swamp vegetation
A crater lake is a lake that forms in a volcanic crater or caldera, such as a maar. Sometimes lakes which form inside calderas are called caldera lakes, but this distinction is not made. Crater lakes covering active volcanic vents are sometimes known as volcanic lakes, the water within them is acidic, saturated with volcanic gases, cloudy with a strong greenish color. For example, the crater lake of Kawah Ijen in Indonesia has a pH of under 0.5. Lakes located in dormant or extinct volcanoes tend to have fresh water, the water clarity in such lakes can be exceptional due to the lack of inflowing streams and sediment. Crater lakes form; the water may come from groundwater circulation or melted ice. Its level rises until an equilibrium is reached between the rates of outgoing water. Sources of water loss singly or together may include evaporation, subsurface seepage, and, in places, surface leakage or overflow when the lake level reaches the lowest point on its rim. At such a saddle location, the upper portion of the lake is contained only by its adjacent natural volcanic dam.
If the volcanic dam portion erodes or fails catastrophically, the occurrence produces a breakout or outburst flood. With changes in environmental conditions over time, the occurrence of such floods is common to all natural dam types. A well-known crater lake, which bears the same name as the geological feature, is Crater Lake in Oregon, it is located in the caldera of Mount Mazama. It is the deepest lake in the United States with a depth of 594 m. Crater Lake is fed by falling rain and snow, with no inflow or outflow at the surface, hence is one of the clearest lakes in the world; the highest volcano in the world, 6,893-m Ojos del Salado in Chile, has a permanent crater lake about 100 m in diameter at an elevation of 6,390 m on its eastern side. This is most the highest lake of any kind in the world. Due to their unstable environments, some crater lakes exist only intermittently. Caldera lakes in contrast can be quite long-lasting. For instance, Lake Toba formed after its eruption around 75,000 years ago.
At a size of around 100 km by 30 km in extent and 505 m deep at its deepest point, Lake Toba is the largest crater lake in the world. While many crater lakes are picturesque, they can be deadly. Gas discharges from Lake Nyos suffocated 1,800 people in 1986, crater lakes such as Mount Ruapehu's contribute to destructive lahars. Certain bodies of water, although their formation is directly related to volcanic activity, are not referred to as crater lakes, including: Lakes created by volcanic dams due to lava flowing outside of the volcanic edifice/caldera Closed atoll lagoons, whose formation process implies subsequent biogeomorphologic processes Ponds encountered at the bottom of waterfalls occurring in volcanic canyons in a volcanic context, but not within a volcanic edifice/caldera Lakes can fill impact craters, but these are not referred to as crater lakes. Examples include Lake Bosumtwi in Ghana and Siljan in Sweden. More they can fill craters caused by artificial explosions, such as the radioactive Lake Chagan in Kazakhstan.
Some geomorphological features, when filled with water, can sometimes be confused with crater lakes: Pingos whose summital part has collapsed Sinkholes, such as Otjikoto Lake in NamibiaSome circular open-pit mines can present a similar appearance, such as Big Hole in Kimberley, South Africa, a diamond mine where water has accumulated in the artificially created depression. Lava lake – Molten lava contained in a volcanic crater Volcanic crater – Roughly circular depression in the ground caused by volcanic activity Caldera – Cauldron-like volcanic feature formed by the collapse of a magma chamber Types of volcanic eruptions – Basic mechanisms of eruption and variations Maar – Low-relief volcanic crater Atoll – Ring-shaped coral reef formed over a subsiding oceanic volcano, with a central lagoon and islands around the rim Impact crater – Circular depression on a solid astronomical body formed by a hypervelocity impact of a smaller object Delmelle, Pierre. "Volcanic Lakes". In Sigurdsson, Haraldur.
Encyclopedia of Volcanoes. San Diego: Academic Press. Pp. 877–895. ISBN 978-0-12-643140-7. Varekamp, Johan C.. "Crater Lakes". Journal of Volcanology and Geothermal Research. 97: 1–508. Bibcode:2000JVGR...97....1C. doi:10.1016/S0377-027300167-5. Pasternack, G. B.. C.. "Volcanic lake systematics I. Physical constraints". Bulletin of Volcanology. 58: 526–538. Bibcode:1997BVol...58..528P. Doi:10.1007/s004450050160. Kusakabe, Minoru, ed.. "Geochemistry of Crater Lakes". Geochemical Journal. 28: 137–306. Doi:10.2343/geochemj.28.137. IAVCEI Commission of Volcanic Lakes IAVCEI Commission of
Lake Benalla, an artificial lake located in Benalla in the High Country region of Victoria, was created in the 1970s. In 2010, more than one hundred residents surrounding the lake were evacuated from their homes at Benalla; the river peaked in the city at 4.1 metres, 40 centimetres above its major flood level. A retaining wall built in 1960 to ward off floods kept the flood water level under control; the Benalla Botanical Gardens are located on the shore of Lake Benalla. The lake is crossed by the Hume Freeway. List of lakes of Australia
A lake is an area filled with water, localized in a basin, surrounded by land, apart from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, therefore are distinct from lagoons, are larger and deeper than ponds, though there are no official or scientific definitions. Lakes can be contrasted with rivers or streams, which are flowing. Most lakes streams. Natural lakes are found in mountainous areas, rift zones, areas with ongoing glaciation. Other lakes are found along the courses of mature rivers. In some parts of the world there are many lakes because of chaotic drainage patterns left over from the last Ice Age. All lakes are temporary over geologic time scales, as they will fill in with sediments or spill out of the basin containing them. Many lakes are artificial and are constructed for industrial or agricultural use, for hydro-electric power generation or domestic water supply, or for aesthetic, recreational purposes, or other activities.
The word lake comes from Middle English lake, from Old English lacu, from Proto-Germanic *lakō, from the Proto-Indo-European root *leǵ-. Cognates include Dutch laak, Middle Low German lāke as in: de:Wolfslake, de:Butterlake, German Lache, Icelandic lækur. Related are the English words leak and leach. There is considerable uncertainty about defining the difference between lakes and ponds, no current internationally accepted definition of either term across scientific disciplines or political boundaries exists. For example, limnologists have defined lakes as water bodies which are a larger version of a pond, which can have wave action on the shoreline or where wind-induced turbulence plays a major role in mixing the water column. None of these definitions excludes ponds and all are difficult to measure. For this reason, simple size-based definitions are used to separate ponds and lakes. Definitions for lake range in minimum sizes for a body of water from 2 hectares to 8 hectares. Charles Elton, one of the founders of ecology, regarded lakes as waterbodies of 40 hectares or more.
The term lake is used to describe a feature such as Lake Eyre, a dry basin most of the time but may become filled under seasonal conditions of heavy rainfall. In common usage, many lakes bear names ending with the word pond, a lesser number of names ending with lake are in quasi-technical fact, ponds. One textbook illustrates this point with the following: "In Newfoundland, for example every lake is called a pond, whereas in Wisconsin every pond is called a lake."One hydrology book proposes to define the term "lake" as a body of water with the following five characteristics: it or fills one or several basins connected by straits has the same water level in all parts it does not have regular intrusion of seawater a considerable portion of the sediment suspended in the water is captured by the basins the area measured at the mean water level exceeds an arbitrarily chosen threshold With the exception of the seawater intrusion criterion, the others have been accepted or elaborated upon by other hydrology publications.
The majority of lakes on Earth are freshwater, most lie in the Northern Hemisphere at higher latitudes. Canada, with a deranged drainage system has an estimated 31,752 lakes larger than 3 square kilometres and an unknown total number of lakes, but is estimated to be at least 2 million. Finland has larger, of which 56,000 are large. Most lakes have at least one natural outflow in the form of a river or stream, which maintain a lake's average level by allowing the drainage of excess water; some lakes do not have a natural outflow and lose water by evaporation or underground seepage or both. They are termed endorheic lakes. Many lakes are artificial and are constructed for hydro-electric power generation, aesthetic purposes, recreational purposes, industrial use, agricultural use or domestic water supply. Evidence of extraterrestrial lakes exists. Globally, lakes are outnumbered by ponds: of an estimated 304 million standing water bodies worldwide, 91% are 1 hectare or less in area. Small lakes are much more numerous than large lakes: in terms of area, one-third of the world's standing water is represented by lakes and ponds of 10 hectares or less.
However, large lakes account for much of the area of standing water with 122 large lakes of 1,000 square kilometres or more representing about 29% of the total global area of standing inland water. Hutchinson in 1957 published a monograph, regarded as a landmark discussion and classification of all major lake types, their origin, morphometric characteristics, distribution; as summarized and discussed by these researchers, Hutchinson presented in it a comprehensive analysis of the origin of lakes and proposed what is a accepted classification of lakes according to their origin. This
Lake Connewarre, a shallow estuarine 880-hectare lake on the Barwon River, is located on the Bellarine Peninsula southeast of Geelong in the Australian state of Victoria. It is adjacent to, downstream from, the freshwater Reedy Lake. Lake Connewarre is linked to the sea by the mangrove-fringed channel of the lower Barwon River estuary, resulting in the lake being subject to tidal flows, with a weir at the inflow to the lake preventing saline water progressing upstream. Lake Connewarre forms part of the Port Phillip Bay and Bellarine Peninsula Ramsar Site as a wetland of international importance, with much of the wetland area part of the Lake Connewarre State Game Reserve. However, most of the land surrounding Lake Connewarre has been cleared for agricultural purposes resulting in environmental degradation. Water pollution from upriver has resulted in a drop in water quality, reduced inflows to the lake have caused silting problems; the lake is shallow being less than one metre in depth and unsuitable for boating.
The lake and its associated wetlands are part of the Bellarine Wetlands Important Bird Area because of its conservation significance for several species of waders and the orange-bellied parrot. The lake is fished commercially for short-finned eel, it usually contains yellow-eye mullet, black bream and Australian salmon. Other fish may be present, depending on salinity levels. List of lakes of Victoria Corangamite Catchment Management Authority "Lake Connewarre State Game Reserve". Parks Victoria. Government of Victoria. 2011
A maar is a broad, low-relief volcanic crater caused by a phreatomagmatic eruption. A maar characteristically fills with water to form a shallow crater lake which may be called a maar; the name comes from a Moselle Franconian dialect word used for the circular lakes of the Daun area of Germany. Maars are shallow, flat-floored craters that scientists interpret as having formed above diatremes as a result of a violent expansion of magmatic gas or steam. Maars range in size from 60 to 8,000 m from 10 to 200 m deep. Most maars have low rims composed of a mixture of loose fragments of volcanic rocks and rocks torn from the walls of the diatreme. Maar lakes referred to as maars, occur when groundwater or precipitation fills the funnel-shaped and round hollow of the maar depression formed by volcanic explosions. Examples of these types of maar are the three maars at Daun in the Eifel mountains of Germany. A dry maar results when a maar lake dries out, becomes aggraded or silted up. An example of the latter is the Eckfelder Maar.
Near Steffeln is the Eichholzmaar which has dried out during the last century and is being renaturalised into a maar. In some cases the underlying rock is so porous. After winters of heavy snow and rainfall many dry maars fill and temporarily with water; the largest known maars are found on the Seward Peninsula in northwest Alaska. These maars range in size from 4,000 to 8,000 m in diameter and a depth up to 300 m; these eruptions occurred in a period of about 100,000 years, with the youngest occurring about 17,500 years ago. Their large size is due to the explosive reaction that occurs when magma comes into contact with permafrost. Hydromagmatic eruptions are explosive when the ratio of water to magma is low. Since permafrost melts it provides a steady source of water to the eruption while keeping the water to magma ratio low; this produces the explosive eruptions that created these large maars. Examples of the Seward Peninsula maars include North Killeak Maar, South Killeak Maar, Devil Mountain Maar and Whitefish Maar.
Maars occur in western North America, Patagonia in South America, the Eifel region of Germany, in other geologically young volcanic regions of Earth. Elsewhere in Europe, La Vestide du Pal in the Ardèche department of France provides a spectacular example of a maar visible from the ground or air. Kilbourne Hole and Hunt's Hole, in southern New Mexico near El Paso, are maars; the Crocodile Lake in Los Baños in the Philippines was thought of as a volcanic crater is a maar. The notorious, carbon dioxide-saturated Lake Nyos in Africa is another example. An excellent example of a maar is Zuni Salt Lake in New Mexico, a shallow saline lake that occupies a flat-floored crater about 6,500 ft across and 400 ft deep, its low rim is composed of loose pieces of basaltic lava and wall rocks of the underlying diatreme, as well as random chunks of ancient crystalline rocks blasted upward from great depths. Maars in Canada are found in the Wells Gray-Clearwater volcanic field of east-central British Columbia and in kimberlite fields throughout Canada.
A notable field of maars is found in the Pali-Aike Volcanic Field in South America. And in the Sudanese Bayuda Volcanic Field; the Auckland volcanic field in the urban area of Auckland, New Zealand has several maars, including the accessible Lake Pupuke in the North Shore suburb of Takapuna. One of the most notable craters misidentified. In the Volcanic Eifel there are about 75 maars; these include water-filled maar lakes. Both types, lake-filled maars and dry maars, are typical of the Volcanic Eifel; the last eruptions took place at least 11,000 years ago and many maars in the Eifel are older. For this reason many are heavily eroded and their shapes and volcanic features are not as obvious as those of more recent or active maars elsewhere in the early; the maars of the Eifel are well preserved. In the Eifel and Volcanic Eifel there are numerous dry maars: Mosbrucher Weiher Booser Doppelmaar Dreiser Weiher Dürres Maar Duppacher Weiher Geeser Maar Eckfelder Maar Eigelbacher Maar Hitsche Maar Immerather Risch Gerolsteiner Maar Schalkenmehrener Maar E Schönfelder Maar Steffelner Laach or "Laach Maar" Dehner Maar Walsdorfer Maar Wollmerather Maar The following volcanic features are colloquially referred to as a "maar" or "maar lake", although they are not speaking, maars: Windsborn Crater Lake and Hinkelsmaar in theManderscheid Volcano Group near Bettenfeld, crater lakes of the Mosenberg Laacher See near Maria Laach, lake in a caldera