Cameroon: Lake Nyos is in a mess; In August 1986, a deadly gas leak from Lake Nyos killed over 1,800 people in Cameroon. Now there are fears that the dam may collapse within five to 10 years and kill more people. Tansa Musa reports from Yaounde.

When Dr Isaac Njilah, a geo-environmental scientist at the University of Yaounde, said last August that the natural dam holding back the water of Lake Nyos in northwestern Cameroon was fragile and could collapse at any time, his colleagues at the state-run Institute of Mining and Geological Research (IMGR) rubbished his claim as too alarmist. But two UN experts invited by the government to look at the dam not only confirmed Njilah's claim but also declared that the dam could collapse within five to 10 years, risking the lives of some 10,000 people downstream in Cameroon and Nigeria.

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The stark warning reminded Cameroonians of the tragic event of 21 August 1986 when a cloud of toxic gas escaped from the bottom of the lake, killing over 1,800 people and 4,000 livestock in surrounding villages. About 3,000 other people were displaced and confined in temporary shelters on nearby hills.

It was the largest gas disaster ever recorded anywhere in the world and thus focused the attention of the international scientific community on the little known lake. Until today the disaster remains the most tragic natural disaster in Cameroon because of its high death toll, loss of wildlife and the number of displaced people.

In response to the disaster, the government convened a series of scientific conferences which eventually identified the poisonous gas as carbon dioxide that had accumulated at the bottom of the lake for centuries and had been triggered upwards by some earth movement. To prevent another disaster, they recommended a controlled release of the carbon dioxide dissolved in deep water. Five pipes were to be installed in the lake to drain the gas, although only one was eventually built. Lake Nyos lies in the throat of an old volcanic line in the Oku volcano field that runs from Pagalu island in the Atlantic Ocean through Mount Cameroon to the Adamawa Plateau in Nigeria.

Last August, after a series of study trips to the lake, Dr Njilah warned that the natural dam holding back the water of the lake was being steadily weakened by erosion and could give way very soon. The region, he added, could face a much worse disaster if the dam collapsed. It would unleash a surge of 50 million cubic metres of water downhill that could drown as many as 10,000 people in Cameroon and Nigeria. Njilah, therefore, urged the governments of Cameroon and Nigeria to send engineers to reinforce the dam and install a concrete spillway to drain excess water, as well as set up more tubes to release the carbon dioxide that have continued to collect in the lake at an alarming rate.

But Dr Greg Tanyi Leke of the Institute of Mining and Geological Research (IMGR) dismissed Njilah's warning as "too alarmist". He, however, conceded that erosion was undermining the barrier at the lip of the lake. "The dam is certainly fragile," Leke said, "but its collapse is not imminent. However, if nothing is done over time, the double effect of internal and surface erosion will result in the failure or collapse of the dam." Leke would not give any timeframe.

The controversy that ensued after his intervention compelled the government to invite UN experts to look at the dam. Olaf Van Duin and Nisa Nurmohamed from The Netherlands were dispatched to Cameroon by the UN to assess the stability of the dam. After three days of inspection, the two vindicated Njilah and said the dam could possibly collapse within the next five to 10 years. They called for urgent measures to be taken to prevent it, and also to facilitate the early return of over 12,000 people and their offspring who are still living in camps up the hills around the lake, 19 years after the 1986 gas disaster.

After the UN report, the government said it was looking for funds to implement the recommendations, but almost a year later, nothing much has been done. Perhaps, now that Cameroon has reached the completion point of the Highly Indebted Poor Country (HIPC) initiative, and is benefiting from substantial debt relief, the government can have money for the Lake Nyos project.