Kivu lakeMethane
Gas Extraction 		Putting methane
to work		 Natural hazards

CONDUCTIVITY MEASUREMENTS

 

One can notice on the figure below that the dissolved ion content is the most important parameter in determining density variation. At first sight this ion content is linked by a rule of proportionality to electrical conductivity.

Measuring conductivity is relatively easy, either in situ using a CTD (Conductivity, Temperature, Depth) gauge, or in the laboratory on samples taken from different depths.

A vertical contour offering excellent spatial definition was realised using a Seabird CTD SBE39. On this conductivity curve the different homogenous layers of the lake are quite clearly visible, separated by layers of a high gradient of density.

On the figure, for example, the two homogenous layers between 280 and 300 m and 330 and 355 m are apparent. We have also taken a large number of water samples from different depths (either by pumping or by using the auto-siphon technique). The conductivity of these samples has been measured and appears on the figure as blue stars as well as the CTD contour already shown. Note that the two curves are very similar.

Variation of conductivity curves : in red is the conductivity obtained using the Seabird CTD SBE39 in January-February 2002 ; the blue points were obtained from water samples taken by pump or by auto-siphon.