|
A lake is an area of variable size filled with water, localized in a basin, that is 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 (except for sea lochs in Scotland and Ireland), and therefore are distinct from lagoons, and are also larger and deeper than ponds, though there are no official or scientific definitions.〔(【引用サイトリンク】accessdate=2008-06-25 )〕 Lakes can be contrasted with rivers or streams, which are usually flowing. However most lakes are fed and drained by rivers and streams. Natural lakes are generally found in mountainous areas, rift zones, and areas with ongoing glaciation. Other lakes are found in endorheic basins or 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 slowly 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 or recreational purposes. == Etymology, meaning, and usage of "lake" == The word ''lake'' comes from Middle English ''lake'' ("lake, pond, waterway"), from Old English ''lacu'' ("pond, pool, stream"), from Proto-Germanic *''lakō'' ("pond, ditch, slow moving stream"), from the Proto-Indo-European root *''leǵ-'' ("to leak, drain"). Cognates include Dutch ''laak'' ("lake, pond, ditch"), Middle Low German ''lāke'' ("water pooled in a riverbed, puddle"), German ''Lache'' ("pool, puddle"), and Icelandic ''lækur'' ("slow flowing stream"). Also related are the English words ''leak'' and ''leach''. There is considerable uncertainty about defining the difference between lakes and ponds, and 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 simply 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 completely excludes ponds and all are difficult to measure. For this reason, simple size-based definitions are increasingly used to separate ponds and lakes. One definition of ''lake'' is a body of water of or more in area; however, others have defined lakes as waterbodies of and above, or and above 〔(【引用サイトリンク】title=Information Sheet on Ramsar Wetlands (RIS) )〕 (see also the definition of "pond"). Charles Elton, one of the founders of ecology, regarded lakes as waterbodies of or more. The term ''lake'' is also used to describe a feature such as Lake Eyre, which is 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'', and 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, almost every lake is called a pond, whereas in Wisconsin, almost every pond is called a lake." One hydrology book proposes to define the term "lake" as a body of water with the following five chacteristics: * it partially or totally fills one or several basins connected by straits〔 * has essentially the same water level in all parts (except for relatively short-lived variations caused by wind, varying ice cover, large inflows, etc.)〔 * it does not have regular intrusion of seawater〔 * a considerable portion of the sediment suspended in the water is captured by the basins (for this to happen they need to have a sufficiently small inflow-to-volume ratio)〔 * the area measured at the mean water level exceeds an arbitrarily chosen threshold (for instance, one hectare)〔 With the exception of the seawater intrusion criterion, the others have been accepted or elaborated upon by other hydrology publications. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「lake」の詳細全文を読む スポンサード リンク
|