"Lake" - what is it, definition of the term
The term refers to a sizable, naturally occurring or artificial inland water body, typically filled with fresh water, entirely surrounded by land, and exhibiting a relatively stable surface area and depth compared to flowing streams. Such formations arise from geological processes like glaciation, tectonic movement, or volcanic craters, and they act as reservoirs for precipitation, groundwater, or runoff, supporting diverse aquatic ecosystems.
Detailed information
Inland water bodies formed by the accumulation of surface runoff, groundwater inflow, or glacial melt often occupy depressions in the terrain. These features exhibit a defined basin surrounded by higher ground, retaining water for extended periods. Their dimensions range from a few hectares to several thousand square kilometers, and depth may vary from a few meters to over a thousand meters in the deepest examples.
Formation processes include tectonic subsidence, volcanic crater collapse, glacial scouring, and river meander abandonment. Tectonic basins arise when crustal plates shift, creating depressions that fill with water. Volcanic craters become water-filled when eruptions leave behind circular hollows. Glacial activity carves out overdeepened valleys that later host permanent water.
Classification distinguishes between oligotrophic, mesotrophic, and eutrophic systems based on nutrient concentrations and biological productivity. Oligotrophic basins contain low nutrient levels, clear water, and limited plant growth. Mesotrophic bodies exhibit moderate nutrient content and balanced biotic activity. Eutrophic environments have high nutrient loads, often resulting in dense algal proliferation and reduced oxygen levels.
Key physical parameters include surface area, maximum depth, volume, residence time, and thermal stratification. Seasonal temperature gradients can produce distinct layers: a warm upper zone, a cooler middle zone, and a cold bottom zone. Stratification influences dissolved oxygen distribution, affecting fish habitats and microbial processes.
Ecological functions encompass habitat provision for fish, amphibians, birds, and invertebrates; nutrient cycling; and carbon sequestration. Sediment accumulation at the basin floor records climatic and geological history, offering data for paleoenvironmental reconstruction.
Human interactions comprise water supply for drinking, irrigation, and industrial use; recreation such as boating and swimming; and hydroelectric power generation. Management practices address water quality preservation, invasive species control, and sustainable extraction rates.
Geographically, these water bodies are present on all continents, with higher densities in glaciated regions and tectonically active zones. Examples include large inland reservoirs in North America, deep alpine basins in the Andes, and extensive lowland basins in the African Rift Valley.