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Water stagnation occurs when water stops flowing. Stagnant water can be a major environmental hazard.
Malaria and dengue are among the main dangers of stagnant water, which can become a breeding ground for the mosquitoes that transmit these diseases.
Stagnant water can be dangerous for drinking because it provides a better incubator than running water for many kinds of bacteria and parasites. Stagnant water can be contaminated with human and animal feces, particularly in deserts or other areas of low rainfall. Water stagnation for as little as six days can completely change bacterial community composition and increase cell count.
Stagnant water may be classified into the following basic, although overlapping, types:
To avoid ground and surface water stagnation, drainage of surface and subsoil is advised. Areas with a shallow water table are more susceptible to ground water stagnation due to the lower availability of natural soil drainage.
Some plants prefer flowing water, while others, such as lotuses, prefer stagnant water.
Various anaerobic bacteria are commonly found in stagnant water. For this reason, pools of stagnant water have historically been used in processing hemp and some other fiber crops, as well as linden bark used for making bast shoes. Several weeks of soaking makes bast fibers easily separable due to bacterial and fermentative processes known as retting.
Stagnant water is the favorite breeding ground for a number of insects.