Cameroon has many potentially dangerous lakes, which contain gas. Yet the authorities have done very little to mitigate the resulting risks.
On August 29, 2022, a sudden change in the color and smell of Lake Kuk in northwestern Cameroon, aroused anxiety and panic among residents. These fears are fueled by an incident 36 years ago at Lake Nyos, just 10km away.
On August 21, 1986, Lake Nyos emitted deadly gases (mainly carbon dioxide) which asphyxiated 1 people and approximately 746 head of livestock. It was not the first such incident. Two years earlier, Lake Monoum, about 8 km southwest of Lake Nyos, had kill 37 personnes.
According to researches undertaken to find out the cause of the Lake Nyos disaster, carbon dioxide – released by the Earth's mantle – had accumulated at the bottom of the lake for centuries. A sudden disturbance of the waters of the lake, due to a landslide, has resulted a sudden release of approximately 1,24 million tons of carbon dioxide.
Survivors briefly heard a rumble coming from Lake Nyos before an invisible cloud of gas emerged from its depths, killing people, animals, insects and birds in its path down the valley, before dispersing into the atmosphere where he became harmless.
Both Kuk and Nyos are crater lakes, located in an area of volcanic activity known as the Cameroon Volcanic Line. And there are 43 other crater lakes in the region which could contain lethal amounts of gas. Other lakes around the world posing a similar threat include Lake Kivu on the border of Rwanda and the Democratic Republic of Congo, Lake Ngozi in Tanzania and Lake Monticchio in Italy.
After Lake Nyos erupted, its water had turned a dark red color and survivors had reported a rotten egg smell. These are the same characteristics that have recently been observed at Lake Kuk. The change in color of Lake Nyos had only been noticed after the gas explosion.
According to an press release, heavy rain has a connection with the smell and color change of Lake Kuk. The tens of thousands people living around the lake were asked to "remain calm, but vigilant and to constantly inform the administration of any other incident observed".
As a geologist and expert in disaster management, I believe that efforts to address and manage the danger of crater lakes in the region are insufficient.
To begin with, it is important to know which lakes are at risk of “exploding”.
The first checks around some lakes were made a while ago over 30 years and in a shallow way – it was about one team and one occasion. Further investigations and regular monitoring are needed.
Currently, it would appear that of the 43 crater lakes in Cameroon's volcanic line, 13 are deep and large enough to contain lethal amounts of gas. Although 11 are considered relatively safe, two (Enep and Oku lakes) are dangerous.
Research found that the thermal profile (i.e. the way the temperature changes with depth), the amount of dissolved gases, the surface area or volume and the depth of the water are major indicators of the potential of lakes to crater to store large amounts of harmful gases.
The most important risk factors are: large quantities of dissolved gases, maintained under high pressure and at great depths, in lakes containing considerable volumes of water. The risk of explosion is even greater when the lakes are located in large or imposing craters where there are disturbances.
The two lakes that caused fatalities (Nyos and Monoum) are deep and have thermal profiles which increase as one descends in depth. Other lakes are too shallow (less than 40 meters) and have uniform thermal profiles, indicating that they do not contain large amounts of gas.
Investigating all the crater lakes in Cameroon would be a logistical challenge, because it would require significant funding, a diverse scientific team, technical resources and means of transport to reach the lakes. As most of the crater lakes are in remote areas with poor communication network (no roads, railways or airports), it will take a few years to complete such work.
Given that Cameroon has many potentially dangerous crater lakes, it is unacceptable that 36 years after the Lake Nyos disaster, little has been attempted to mitigate the risks posed by other dangerous gas-laden lakes.
Management of dangerous lakes
Kuk Lake has been checked shortly after the Lake Nyos disaster in 1986 and was found to contain no excess carbon dioxide. Given its relatively shallow depth and surface area, the risk of a large amount of gas being trapped is low.
Nevertheless, the authorities should have immediately restricted access to Lake Kuk pending a thorough on-site investigation. The official press release calling for calm was sent just a day after the incident was reported. It is impossible that a scientist could have carried out a physical examination of the lake. The statement said rainfall was responsible for these changes, but it was all based on assumptions.
Kuk Lake could be considered safe, but due to the dynamic and active nature of the Cameroon Volcanic Line, it is possible that volcanic gases could seep into the lake at any time.
A scientific investigation on the spot would make it possible to determine with certainty the abnormal behavior of Lake Kuk. Keeping people at bay until a quick and credible investigation is carried out would be the most rational decision.
An additional step would be to install a carbon dioxide detector near this lake and other potentially dangerous crater lakes. This would serve as an early warning system in the event of a lethal gas emission.
A carbon dioxide early warning system is designed to detect high concentrations of gases in the atmosphere and to issue an alarm signal. Hearing this sound, people are supposed to quickly move away from the lake and take refuge on higher ground. After the Lake Nyos disaster, carbon dioxide detectors and warning systems were installed near Lakes Nyos and Monoum. However, no simulations have been performed to test their effectiveness.
The Directorate of Civil Protection is the agency responsible for coordinating disaster risk management in Cameroon. This agency should liaise with other stakeholders to ensure safety around dangerous lakes in this country. If the authorities are not proactive, the Lake Nyos disaster scenario could repeat itself, with the sudden death of thousands of people and livestock.