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Communities Face Impending Danger From Lake Nyos 

By Edith Wirdze

Many communities and families may be wiped out by flood water which is expected to pour out as a result of the possible breakage of Lake Nyos. This breakage can take place at any moment, according to an article published on October 31 by Sunday Tribune, a Nigerian newspaper. On August 18, 2005, a geologist at the University of Yaounde I, Dr. Isaac Njilah, said the natural dam of the volcanic rock that keeps in the Lake Nyos’ waters could collapse in the near future.

Lake Nyos

Erosion has worn the dam away, causing holes and pockets to develop in the dam’s upper layer and water already was passing through the lower section. Landslides reduced the dam’s strength on the outside. Thus, internal movement of the earth caused by the lake’s volcanic foundation could cause the lake wall to give way, resulting in up to 50 million cubic metres of water folding. It is in this perspective that the alarming bell comes.

According to the report by Kehinde Oyetimi, 200 communities and 200 000 families in Taraba State may be wiped out by floods which are expected as a consequence of the possible breakage of Lake Nyos. This means the figures would increase if the Cameroon communities and families that can be affected are added.

The report indicates that "the threat is real and will happen". Thus, these communities and families are facing impending danger because there is the high possibility that they can be swept away by over 132 million cubic metres of water.

In a release signed by the Public Information Officer and the Assistant Coordinator of the Nigeria’s National Emergency Management, NEMA, Ibrahim Farinloye, the agency stated that "the collapse of the lake of 400-year-old would results into the release of water at an estimated peak discharge of 17,000 cubic metres per second into Kumbi River and would discharge into the Kashimbila River". It was equally stated that "the water would flow downhill, flooding the Northwest province of Cameroon and some frontline states in Nigeria". Thus, the concerned families have been advised to consider a possible relocation.

Public Should Not Panic

The authorities in the National Institute of Geological and Mining Research, Yaounde, have indicated that the above report may be sensational. The Director of the Institute said a team of researchers have been sent to Lake Nyos. He advised that the public will be informed subsequently and should not panic.

Geography

Lake Nyos is a crater lake on the flank of an inactive volcano in the Oku volcanic plain. The lake waters are held in place by a natural dam composed of a volcanic rock. At its narrowest point, the wall measures 10 metres high and 45 metres wide. Magma lies beneath the lake and leaks carbon dioxide into the water, changing it into carbonic acid. Lake Nyos and Lake Monoun in Cameroon as well as Lake Kivu in Rwanda are only three known exploding lakes to be saturated with carbon dioxide.

History

On August 21, 1986 Lake Nyos released a lethal cloud of carbon dioxide that swept through the lower villages of Nyos, Cha Subum, Kam, Munji, and Djingbe asphyxiating more than 1700 people and animals. Never before, a lake has suffocated people and animals on such a scale in a single and brief event. Two years earlier, 37 people had died from such carbon dioxide emissions in Lake Monoun.

It is not known what triggered the 1986 catastrophic out-gassing. Some geologists suspect a landslide whereas others think it was a small volcanic eruption that occurred on the bed of the lake. Others talk of cool rainwater falling on one side of the lake that could trigger the overturn. Whatever the cause, the event resulted in the rapid mixing of the supersaturated deep water with the upper layers of the lake, where the reduced pressure allowed the stored carbon dioxide to effervesce out of solution.

Investigations of the physics and chemistry of lakes Nyos and Monoun revealed that both lakes contained huge amounts of carbon dioxide of 300 millions m³ and 10 millions m³ in Nyos and Monoun respectively. It was seen that this gas is being added at such a rate that saturation could be reached with years in the deep layers of the lakes. To make the lakes safer, there is a degassing project, which extracts in a controlled way, the carbon dioxide they contain.

In addition to the carbon dioxide threat, Lake Nyos also poses a threat as indicated in the above report. This is due to its weakening natural wall. Studies show that a geological tremor could cause this natural dike to give way, allowing water to rush into downstream villages in the Northwest Region of Cameroon right into Nigeria. Apart from the flood water that would wipe away communities, much carbon dioxide would also be released if a breakage occurs.

Possible Solution

According to scientists, a possible way of preventing the catastrophe would be to strengthen the lake wall.  Another way is introducing a channel to allow excess water to drain. If the water level is lowered by about 20 metres, the pressure on the wall would be reduced significantly.
With online reports

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