Flooding, Gas Still Pose Danger at Disaster Lake
WASHINGTON (AP) _ An American scientific team is proposing moves to reduce the danger of another disaster at the African lake where a cloud of gas killed 1,746 people last summer.
An unstable spillway on Lake Nios in Cameroon poses the hazard of a major flood in the area, and another release of deadly gas remains possible, warns a study released Wednesday by the State Department.
The report calls for lowering the lake level to ease the flooding danger, and proposed a method to reduce the amount of carbon dioxide dissolved in the lake.
In addition, dozens of similar area lakes should be studied to see if they pose like dangers, said Dr. Edward J. Koenigsberg of the U.S. Office of Foreign Disaster Assistance.
He said the water in Lake Nios continues to contain high concentrations of dissolved carbon dioxide, raising the possibility of another sudden gas cloud similar to the one last Aug. 21.
The victims of that disaster were smothered by a massive cloud of the gas, which suddenly bubbled out of the lake and rushed down the hillside to overwhelm villagers and their cattle, the study concludes.
The U.S. scientific team will return to Cameroon next month to meet with local officials and scientists from several other nations to compare findings and proposals for preventing further tragedies, Koenigsberg reported.
While investigatiors have concluded that the carbon dioxide cloud killed the vicitims of the disaster, the mechanism that caused it to burst forth from the lake remains in some dispute, Koenigsberg admitted.
American scientists believe the gas, which originated in molten rock deep in the earth, was dissolved in the bottom layers of the lake and suddenly bubbled forth, the way carbon dioxide bubbles out of a soft drink when the bottle cap is removed.
The trigger could have been a storm above the lake, a small landslide, runoff from heavy rains at the time or even seasonal cooling, Koenigsberg said.
Normally, water in lakes like Nios remains very stable, allowing gas concentrations to build up. By contrast, lakes in cooler climates such as the United States have a regular circulation because of seasonal warming and cooling, and that prevents such a buildup of dissolved gas.
Carbon dioxide is invisible and generally considered odorless and tasteless. It can be formed from natural chemical reactions, which is usually how it gets in beer and sparkling wine, where it forms the bubbles.
It also can originate from molten rock, and the lava underlying volcanoes in Cameroon appears to contain large amounts of carbon dioxide.
But French scientists contend a huge bubble of gas from deep in the earth suddenly burst through the lake.
While the cause remains in dispute, Koenigsberg suggested that a major problem continues at a spillway on the lake, which is leaking and could collapse.
Koenigsberg proposed slowly lowering the lake level and then demolishing the spillway, after temporarily relocating area residents.
As to the gas trapped in the lake waters, he said U.S. Environmental Protection Agency officials have proposed a system of deep tubes which could siphon water from the bottom to the surface, allowing carbon dioxide to bubble out gradually. This would take about three years to de-gas the lake, he said, with the release being gradual and thereby less dangerous.
A gas release at Lake Monoun, about 100 miles from Lake Nios, killed 37 people in 1984 he noted, and there are 40 or more lakes in the region located in old volcanic craters, similar to Nios and Monoun.
″Other lakes in northwest Cameroon may also have the potential for the catastrophic release of lethal gases.
While the tragedies in 1984 and 1986 have thrust the problem into the worldwide spotlight, stories of ″exploding lakes″ have been part of the folklore of the region for centuries.