Scientists Tame Cameroon Killer Lake

Scientists Tame Cameroon Killer Lake

By Ntaryike Divine Jr.

Douala, Cameroon

3 March 2011

On a quiet August night in 1986, Lake Nyos in northwestern Cameroon coughed up lethal clouds of carbon dioxide, choking over 1,700 people and 3,500 livestock in adjacent villages.  Twenty five years later, scientists claim they have successfully tamed the killer lake through a degassing process in which accruing carbon dioxide is siphoned off its bottom water layers.

Like a naturally beautiful woman without makeup, Lake Nyos, perched on the flank of an extinct volcano in Cameroon's remote northwest hardly leaves sightseers indifferent.  Now, with three manmade fountains gracing its blue surface, the generally tranquil water body appears even more elegant.

But all that splendor constitutes a dangerous masquerade.  Calamity lurks beneath the crater lake located along an area of volcanic activity stretching southwest to Mt Cameroon. 

The lake first captured the attention of the world on August 21, 1986, when it abruptly discharged large clouds of carbon dioxide which asphyxiated over 1,700 people and thousands of livestock in nearby villages. The mass suffocation came two years after 37 people were killed in similar circumstances at Lake Monoun, sixty miles to the southeast.

Scientists rushed to the scene from across the world.  They agreed that degassing the lake by installing pipes to suck up gas-filled water from its bottom layers and allowing the carbon dioxide leak out in safe quantities atop was the best bet in avoiding a recurrence.

The fountains are actually the visible parts of those vent tubes, the last of which was vertically mounted in the 200-meter-deep lake in March, ending a venture embarked upon in 2001 and considerably snail-paced by sluggish funding.

Scientists say the suction pipes will pump out some 200 million cubic meters of carbon dioxide trapped in the lake’s bottom layers over the next two years.  Michael Halbwachs, currently heads the French gas-extraction company DATA Environnement, He says the process will eradicate all lingering dangers of another toxic gas explosion.

“The system is self-powered and will permanently pump up water heavily saturated with CO2 from the lake bottom.  As the water rises, its pressure drops implying that higher pressures at the bottom layers will continue to drive the process.  Over long periods, carbon dioxide has been seeping into the bottom layers from a magma [or molten rock] chamber beneath.  Progressively, the water becomes supersaturated with CO2, requiring a landslide, an earthquake, heavy rainfall or rising temperatures to detonate an explosion in which large amounts of CO₂ bubble upwards and burst out through the lake surface,” he explains.

CO₂ is heavier than air, and so once emitted, it sinks to the ground, displacing breathable air upwards. As a result, life forms breathing oxygen for survival are suffocated.  Geologists call the phenomenon limnic eruption.  They say before a lake is saturated, it behaves like an un-opened carbonated soft drink.

  

In both cases, the CO₂ dissolves much more readily at higher pressure. That’s why bubbles in a can of soda for example, only form after the drink is opened, releasing the pressure and forcing bubbles of CO2 out of the solution.

To date, the phenomenon has been observed only twice in Cameroon.   However, a third lake, the Kivu on the DR Congo and Rwanda border, is known to contain even greater amounts of dissolved CO_2.   It is 2,000 times larger than Lake Nyos, with over two million people living along its shores.  Scientists say fortunately, it has not attained the required level of CO2 saturation to provoke an eruption.   Ironically, it is a potential source of wealth, holding vast stocks of methane.  Halbwachs is at work there, fine-tuning several commercial projects to extract the gas and turn it into useful energy.

Lake Nyos lacks such endowments, but remains a cherished place despite the sad memories.  Long before the completion of the degassing project, the few nostalgic survivors of the 1986 disaster had begun resettling their once-abandoned ancestral lands.  The successful conclusion of the degassing venture plus security guarantees including the erection of an alarm system at the lake gateway is attracting more people including mostly farmers and cattle grazers.

However, many complain that half a century later, the persisting remoteness of the increasingly tourist destination is deterring potential investors. The returnees complain they lack roads, hospitals and other basic social amenities.  They are demanding more government assistance.

Elsewhere, another problem remains unresolved.  The lake waters are held in place by a natural dam of volcanic rock. Geologists fear it could collapse in the near future from erosion.  If it gives way, some 50 million cubic meters of water will sweep downhill, wiping out human settlements inhabited by some 10,000 people both in Cameroon and across the border in Nigeria. 

The government has announced plans to artificially reinforce the lake wall with concrete, as well as permanently drain off some of the lake waters to trim down pressure on the wall.  It however remains to be seen when the promises will hop from the drawing boards to reality

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