Kivu lakeMethane
Gas Extraction 		Putting methane
to work		 Natural hazards

WATERS STRUCTURE.

 

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.

The 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.

Vertical section of density, conductivity, temperature and pressure taken together : average of 23 profiles : K. Tietze 1974 - 75.

 

Measurements from February 2002 : to be compared with the previous figure from 1974

 

The 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).

Four 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).