Final step of the 32-year Lake Nyos degassing adventure: Natural CO2 recharge is to be balanced by discharge through the degassing pipes

Abstract In wake of the lakes Monoun and Nyos disasters, the aim of the Nyos Organ Pipes Program was clearly to mitigate the hazard of a limnic eruption at both lakes in the coming decades. Due to the carbon dioxide natural recharge of the Nyos lake water, the self-siphon degassing pipes had been progressively scaled up since 1992 in order to liberate most of the CO2 content of the lake in a reasonable time. One of the pipes was also fine-tuned to exactly counterbalance for the CO2 recharge on the long term. In less than thirty years, both objectives have been met by a team of French scientists, engineers and technicians. Here we show that the continuous operation of no more than a single degassing pipe, as already installed in Lake Nyos since 2001 and refurbished in 2011, could match the natural CO2 recharge rate. The safeguarding, without any human intervention, of a visible water jet, equally feasible at Lake Monoun, will sustain the awareness of scientists and institutions in charge, and will perpetuate their commitment to decrease the risk of a new disaster among the Nyos and Monoun lakeside residents.