Inland Fisheries

4.3.1 Natural Lake

Natural lakes are naturally formed, usually “bowl-shaped” depressions in the land surface that became filled with water over time. These depressions (also called basins) were typically produced as a result of the catastrophic events of glaciers, volcanic activity, or tectonic movements. The age of most permanent lakes usually is of a geological time frame, but with most not much older than 10,000 years. A few are much older, and some ancient lakes may be millions of years old.

Other natural processes that produced lake basins include (i) seepage of water down through layers of soluble rock, (ii) erosion of the land surface by wind action, and (iii) plant growth or animal activity that resulted in damming of the outlet channels from shallow depressions in the land surface. There are literally millions of small lakes around the world, concentrated largely in the temperate and sub-arctic regions. These regions are also characterized by a relative abundance of fresh water. Many more millions of temporary lakes occur in semi-arid and arid regions.