The Concept of the lake. General description – Lake of the Caucasus
Lakes, reservoirs slow water exchange, not communicating with the ocean. From the rivers of the lake characterized by the absence of the channel, from the sea — the lack of a direct connection with the ocean. Lakes are called inland waters sushi with stagnant or slowly flowing water.
Lakes regulate the flow of rivers, holding in its hollow basins of water and placing them in other periods. In the waters of the lakes occurring chemical and biological reactions. Some elements are transferred from water into bottom sediments, others Vice versa. In some lakes, mostly without drain, in connection with the evaporation of water increases the concentration of salts. The result is considerable variation in the salinity and salt composition of the lakes.
Due to the significant thermal inertia of large water mass of the lake softens the climate of adjacent areas, reducing the annual and seasonal variation of meteorological elements.
The shape, size and bottom topography of the lake basin change significantly with the accumulation of sediment. The overgrowing of lakes creates new landforms, flat or even convex. Lakes and especially reservoirs often create backwater groundwater, causing waterlogging of nearby land areas. As a result of continuous accumulation of organic and mineral particles in lakes are formed by a thick series of sediments. These deposits are modified with further development of reservoirs and turning them into swamps or dry land. Under certain conditions they are converted to rocks of organic origin. 
In every lake there are three interrelated components:
§ water mass composed not only of water but also of dissolved substances;
§ vegetation and fauna of the reservoir.
Talking about lake bed and the bed of the lake. Lake basin — a depression in the land surface that does not have unilateral slope, and are filled to some level with water. Part of the lake basin filled with water, box.
, i.e. the flow of water in the lake is due to:
§ clay courts and underground power;
§ supply of water from rivers and streams flowing into the lake;
§ condensation of atmospheric moisture.
The regime of the lakes
. Of receipts and consumption of water distinguish lake:
well flow, into which empties one or several rivers and one follows;
slowly flowing or intermittently flowing in flows into one river, but the flow is negligible;
undrained, into which empties one or several rivers, but no outflows;
deaf, or closed — not having a river flow. Such lakes are found in the tundra, taiga and steppe.
All lakes experience water level fluctuations. The magnitude of the fluctuations in different lakes are different. Thus, in flow-through lakes are oscillations about H m, and in slowly flowing up to 1,5 m, in a closed — up to 1 m. there Are seasonal and perennial fluctuations in the level. Mostly they depend on the rains.
begins with the formation of the basin. The origin of the basin largely determines its size and shape. The origin of the lake basins are divided into several genetic types.
Tectonic lakes occur in connection with the formation of depressions of the earth’s crust, cracking, discharges, grabens; plenty of depth and steepness of slopes.
Volcanic lakes occupy the craters of extinct volcanoes filled with water.
Glacial lakes are formed as a result of destructive and constructive activity of glaciers (modern and ancient).
Water-accumulating and water-erosion lakes are created by the activity of rivers (oxbow lakes) or are the sea flooded parts of the river valleys (estuaries, lagoons), separated from the sea by the accumulation of sediment.