Concerning the physico-chemical study of the lake we
have limited ourselves on the one hand to those aspects having direct consequences
on natural dangers and on the other to the conception of methane extraction equipment.
We have tried particularly hard to determine accurately the density profile of
the water which affects the risk of gas emanation and the process of the discharge
of ion and CO2 charged water in the degassing device.
waters of Lake Kivu manifest a particularly obvious 'stair-like' stratified structure
following the variations of their physico-chemical parameters with depth. The
exact explanation of this phenomenon of stratification is complex. The waters
of the lake are made up of homogenous layers - where mixing by convection easily
takes place - separated by layers with a high density gradient which act as barriers
to the mixing process.
A Franco-Swiss team of scientists is studying the physico-chemical
makeup of the lake, its evolution through time, the origin of the dissolved gases
and an evaluation of the risk of a gas explosion.
analysis of the gas content profiles of Lake Kivu indicate that the gas deposits
are confined to the interior of the depth contour - 270m - and that a layer favouring
the harnessing of the waters of Lake Kivu is to be found at a depth of approximately
350 m. Analysis of water taken from this depth shows that it contains dissolved
gases of the order of 2,5Lgas/Leau... This gas is made up of 5/6 carbon dioxide
CO2 (2,1 LCO2/Leau), and 1/6 methane CH4 (0,425 LCH4/Leau).
field trips to study the physico-chemical makeup of the lake were undertaken in
2002, 2003 and 2004. During these field trips we tried to determine exactly the
variations of some parameters having a direct influence on the degassing technique,
all the while taking into account the environmental impact of the future gas extraction
plant on the lacustrine ecosystem as well as the eventual risk of a gas emanation
(of the kind responsible for the explosion at Lake Nyos).