NOVELTY - The installation for extracting methane gas dissolved in water of large depth, comprises an extraction column (3) of which an inlet (5) opens in a water layer containing gas to be extracted dissolved in high concentration and of which an outlet (7) is connected to a water/gas separator (9), and a unit for sucking water from a low gas concentration layer to be extracted in the flow adjustable extraction column. The suction unit comprises a side valve such as an adjustable flow valve arranged on the extraction column at low layer concentration gas to be extracted.    USE - The installation is useful for extracting methane gas dissolved in water from lake Kivu.    ADVANTAGE - The installation allows complete and reliable extraction of methane gas dissolved in the water with less consumption of energy in an economical and simple manner without the risk of explosion of gas.    DETAILED DESCRIPTION - The installation for extracting methane gas dissolved in water of large depth, comprises an extraction column (3) of which an inlet (5) opens in a water layer containing gas to be extracted dissolved in high concentration and of which an outlet (7) is connected to a water/gas separator (9), and a unit for sucking water from a low gas concentration layer to be extracted in the flow adjustable extraction column. The suction unit comprises a side valve such as an adjustable flow valve arranged on the extraction column at low layer concentration gas to be extracted. A first side valve is laid at a depth of 190-260 m, and a second valve is laid at a depth of 60-190 m. A potential resource layer and a set of lateral valves are present on the extraction column, and are spaced away by 10 m. The diameter of the side valve is less than or equal to the diameter of the extraction column. The inlet of the extraction column is laid in the resource layer between 260-310 m of depth and in that, when fully open, the diameter of the side valve is 0.6 times or 0.4 times the diameter of the extraction column. A unit is arranged for regulating water flow sucked by the water suction unit on the extraction column at a flow to obtain a density of water in outlet of the preset gas/water separator. The adjustment unit comprises a sensor for measuring density of the water in outlet of the gas/water separator, and a flow control module of the suction means is connected to sensor to compare the measurement signal of the sensor with a predetermined set point and for controlling the flow of the suction unit based on the result of the comparison. An INDEPENDENT CLAIM is included for a process for extracting methane gas dissolved in water of large depth.    DESCRIPTION OF DRAWING(S) - The figure shows a simplified schematic view of an installation for extracting methane gas dissolved in water.    Extraction column (3)    Inlet of extraction column (5)    Outlet of extraction column (7)    Gas/water separator (9)    First gas outlet (11)    Second gas outlet. (13)