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The taming of the Lake-
avoiding future disasters in Cameroon
by Garth Cambray
 In the dark of night in 1986 Lake Nyos in Cameroon emitted a huge cloud of carbon dioxide. This heavy gas settled in a thick layer over the area asphyxiating 1800 people and all the animals in the area. Scientists such as H.Sigurdsson, K. Tietze, G.Kling, W.Evans, M.Kusakabe and G.Tanyileke have contributed much to the understanding of this disaster and the prevention of future disasters like it.
Most of us have experienced the explosive release of gas from a carbonated cooldrink bottle. When the bottle is opened and pressure is released, carbon dioxide dissolved in the cooldrink to turns the bottles contents into a stream of foam. In order to carbonate a beverage, it is placed under about 6 atmospheres of pressure, allowing enough carbon dioxide to be forced into the water to allow it to form bubbles at normal atmospheric pressure.
At the bottom of a 200m deep lake, the pressure is considerably higher than this, meaning that if any gas should be released it will dissolve into the water. This process will continue, and if enough gas is released into the lake a point will be reached where the water is almost completely saturated with carbon dioxide. The water in the lake would form layers, with each layer having a specific pressure as a function of its depth, and hence a specific concentration of dissolved oxygen. If water from a lower layer were to move upwards, it would be able to dissolve less carbon dioxide. If it were saturated, carbon dioxide would be released as a bubble, which would rise rapidly causing mixing of layers upwards, causing the release of more carbon dioxide, until eventually the whole lake explodes in a huge cloud of frothy foaming water -like the Lake Nyos disaster.
Lake Nyos is situated in a volcanic basin. Carbon dioxide rising from deep within the earth bubbles into groundwater which then flows into the base of the lake where it accumulates. In order to stop this gas reaching a dangerous concentration in the lake it needs to be continuously removed.
The degassing of the lake has been a co-operative project funded by the US Office of Foreign Disaster Assistance, the French Embassy and Cameroonian government. Polyetheylene tubes with an internal diameter of 14.5 centimetres were soldered together and lowered to the base of the lake at a depth of about 205 metres. Remote valves were then opened causing water to begin rising up the column, at which point it began degassing, rising faster and sucking more up behind it. The end result, a powerful 50 metre plume of soda water spraying above the peaceful surface of lake Nyos on January 30th 2001. It was stable and could be switched on and off allowing the controlled removal of accumulated carbon dioxide gas from the depths of lake Nyos.
In this way, the application of science and relevant technology have allowed mechanisms to be put in place to avert a future disaster of the scale of the Lake Nyos Disaster of 1986 which killed 1800 people.
For further information please visit the projects web-site
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