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Lake Natron and Lake Magadi on opposite sides of the Kenya/Tanzania border are situated in a closed lake basin in the southern part of the Gregory Rift, a branch of Africa's Great Rift Valley. The Magadi-Natron basin has been occupied by a larger body of water on several occasions during late Pliocene and Pleistocene times. Both lakes are saline, but Lake Magadi is the most saline of the lakes in the Gregory Rift. Natron lake is quite shallow, less than 3 m deep, and varies in width depending on its water level, it has a surface area of ca. 1039 km². The Lake Natron brine is found to contain at least 8% per cent Sodium Chloride. It is supplied by hot springs of volcanic origin and by fumerolic emanations from Ol Doinyo Lengai. It is estimated that, at least 2100 km² of the North Western part of the lake is covered with a layer of mixed salts averaging 1.5 metres in thickness. The volcanic rocks in the surrounding areas of the lake, generally present high alkalinity. The younger the age of the volcanic rock is, the higher its alkalinity. In Ol Doinyo Lengai, which is considered to be the youngest volcano, is presenting eruption of carbonates consisting of Sodium Carbonate (Na₂CO₃) and Calcium Carbonate (CaCO₃). In fact Ol Doinyo Lengai is famous for being the only volcano in the world known to have erupted carbonatite lava in historical time.

The alkali salt crust on the surface of Lake Natron is often coloured red or pink by salt-loving microorganisms that live there. The lake is the only breeding area for the 2.5 million endangered Lesser Flamingos that live in the valley. Because of its unique biodiversity, Tanzania named the Lake Natron Basin to the Ramsar List of Wetlands of International Importance on 4 July 2001. More on that aspect here.

The area around Lake Natron is often described as having a desolate and almost lunar beauty, and it attracts lots of tourists from all over the world, including birdwatchers like me. But there is an adder or two under the grass. Threats to the salinity balance from increased fresh water influxes will come from projected logging in Natron watersheds and a planned hydroelectric power plant. Although development plans include construction of a dike at the north end of the lake to contain the fresh water, the threat of dilution to this breeding ground may still be serious.

Worse is the proposed development of a soda ash plant on the very shores of Lake Natron. Local people fear that it would endanger employment gained from tourism which benefits many locals, including women who make and sell beadwork. BirdLife strongly believe that the cumulative impacts from the proposed facility have a high risk of causing extreme detriment to the Lesser Flamingo population should the project be allowed to be developed in Lake Natron area (see here). The Lake Natron Consultative Group rejected the project, saying that the local community will lose their sources of livelihoods owing to over-use of water by the factory and their livestock economy risks being destroyed. The Group insist that the best way to use the natural resources of Lake Natron is to enhance ecotourism which is already thriving.

Soda ash is an essential constituent in the manufacture of glass and important in the production of detergents and industrial chemicals, e.g. for fabric dyeing, pharmaceuticals, baked goods, toothpaste, deodorants and paper production. Magadi Soda Company in Kenya is Africa's largest soda ash manufacturer. Lake Magadi is rarely visited by tourists. The town of Magadi - on the lake's east shore - as well as Lake Magadi are owned and exploited by the Magadi Soda Company. With operations dating to 1911, Magadi Soda is one of Kenya's oldest private firms.

The plant would undoubtedly deliver many jobs for educated and skilled workers (from elsewhere), but not for local people. The short term economic gain may count less than the long term economic loss. The traditional chief from Pinyinyi, one of the villages adjacent to Lake Natron, likened the development to "taking a fish and throwing it into the bush".

• http://www.ndctz.com/sodaash.htm
• http://www.birdlife.org/news/news/2008/01/lake_natron.html
• http://tzcommoncents.wordpress.com/2007/11/12/lake-natron-soda-ash-factory-plan-sinked-for-now/
• http://en.wikipedia.org/wiki/Lake_Natron
• http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=16898
• http://www.ramsar.org/ris/ris_tanzania_natron.htm

Notes:
A salt lake or saline lake has a concentration of salts (mostly sodium chloride = household or kitchen salt or sea salt) and other minerals significantly higher than most lakes (often defined as at least 3,000 milligrams of salt per litre). In many cases, salt lakes have a higher concentration of salt than sea water.
Lakes that contain high concentrations of sodium sulphate are called bitter lakes, and those containing sodium carbonate are called alkali lakes.

Natron is a naturally occurring mixture of sodium carbonate decahydrate (Na₂CO₃·10 H₂O, a naturally occurring form of soda ash) and about 17% sodium bicarbonate (baking soda, NaHCO₃) along with small quantities of household salt (sodium chloride) and sodium sulphate. Natron is white to coloorless when pure, varying to gray or yellow with impurities. Natron deposits occur naturally as a part of saline lake beds in arid environments.

The English word natron is a French cognate derived from the Spanish natrón through the Arabic natrun from Greek nitron, which derived from the Ancient Egyptian word netjeri, stemming from Wadi El Natrun, Egypt. The modern chemical symbol for sodium, Na, is an abbreviation of that element's new Latin name natrium, which was derived from natron.

Most industrially produced sodium carbonate is soda ash, sodium carbonate anhydrate Na₂(CO₃), which is obtained by calcination (dry heating at temperatures of 150 to 200°C) of sodium bicarbonate, sodium carbonate monohydrate, or trona.