REMEMBER LAKE NYOS Disaster 30 Years After

Lake Nyos is a crater lake in the Northwest Region of Cameroon, located about 315 km (196 mi) northwest of Yaoundé. Nyos is a deep lake high on the flank of an inactive volcano in the Oku volcanic plain along the Cameroon line of volcanic activity. A volcanic dam impounds the lake waters.

A pocket of magma lies beneath the lake and leaks carbon dioxide (CO2) into the water, changing it into carbonic acid. Nyos is one of only three known exploding lakes to be saturated with carbon dioxide in this way, the others being Lake Monoun, also in Cameroon, and Lake Kivu in Democratic Republic of Congo.

Lake Nyos had long been quiet before it happened. Farmers and migratory herders in the West African country of Cameroon knew the lake as large, still and blue.

But on the evening of Aug. 21, 1986, farmers living near the lake heard rumbling. At the same time, a frothy spray shot hundreds of feet out of the lake, and a white cloud collected over the water. From the gro?nd, the cloud grew to 328 feet (100 meters) tall and flowed across the land. When farmers near the lake left their houses to investigate the noise, they lost consciousness.

The heavy cloud sunk into a valley, which channelled it into settlements. The High  concentrations  of  CO2  in  nearby  villages  led  to  the  asphyxiation, death of over1786 people, more than 3000 cattle and all forms of animal life within a 50 Km

By Aug. 23, the cloud had mostly blown away, and the silence had lifted. After being unconscious for up to 36 hours, some people revived to find, horrifically, that their family members, neighbours and livestock were dead.

The lake had changed, too. It was now shallower plants and leaves floated in it and its formerly picturesque blue hue had darkened into rust.

What has been done?

1-   We (Cameroon) installed a floating platform on Lake Nyos to measure basic climate variables such as air temperature and humidity, wind, and solar radiation. Sensors were installed to monitor the water temperature, salt content, and the pressure of dissolved gases (carbon dioxide, CO2 and methane, CH4) at two depths in the lake.

2-    Measurements of the total gas pressure in the lake showed that the degassing operation is steadily reducing gas amounts in the bottom of the lake.  The gas pressure at the deepest part of the lake has been reduced by ~2.5 times from a maximum content in 2001 when the first pipe was installed.  The total CO2 in the lake has been reduced by 40% since 2001, from ~710,000 to 425,000 metric tons.

Greenhouse Gases and Air Quality Impacts of Degassing

Recently a concern voiced in the media has been that releasing the CO2 gas from the lakes will contribute negatively to the greenhouse effect and climate warming. This is NOT a valid concern according to scientist because the amount of gas released by the degassing pipes is far too small to have any noticeable impact at any scale. For example, at the most local scale Cameroon have informations from the CO2 warning stations located on the spillway of Lake Nyos and near the town of Njindoun at Lake Monoun that monitor the CO 2 concentrations in the atmosphere (and to warn the local people in the case of a gas release). Analysis of the continuous records of data collected from these stations shows that the gas concentration in the atmosphere is always near ambient, and investigations near the pipes also show that the CO2 concentrations are at safe levels and there is no reduction in air quality around the pipe itself. Even if the releases of CO2 from the pipe discharge are integrated over time, the contribution to greenhouse warming is negligible.

 http://www.dibussi.com/2006/08/the_lake_nyos_d.html

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