Extreme gas loads in lakes (Guadiana Pit, Nyos, Kivu) - their quantification, their origin and the assessment of risks
Guadiana Pit, Nyos, Kivu
Dr. Bertram Boehrer
INF 229, SR 108/110

Several lakes show extreme loads of gases in their deep water. In most cases, volcanic sources are responsible for the high gas charge but also geochemical processes and decomposition of organic material have created gas loads of concern.

We report, how reliable measurements of extreme gas loads could be accomplished [1]. In the case of Lake Kivu 40 billion m³ of exploitable methane could be substantiated, while in Guadiana Pit Lake carbon dioxide loads of nearly three liters of gas per liter of lake water were detected [2]. We report about possibilities to confirm high gas loads by direct measurements of gas pressure or sound speed [3]. In the case of Guadiana Pit Lake, authorities followed the recommendation to remove the gas load artificially to avert the danger of a limnic eruption [4], while in the case of Lake Kivu, prescriptions for the survey of the lake have been issued by an international expert team for the period of methane exploitation. Finally, we show results from noble gas thermometry for the deep water of Lake Kivu to quantitatively separate the effect of equilibration temperatures from possible previous gas evasion by large scale ebullition [5].

[1] Boehrer et.al. (2019):  Gas in Lake Kivu. Hydrol. Earth Syst. Sci. 23 (11), 4707 – 4716.

[2] Boehrer et.al. (2016):  Assessing Guadiana pit lake. Sci. Total Environ. 563-564 , 486 - 477

[3] Boehrer et.al. (2021): Carbon Dioxide in Lake Nyos. Front. Earth Sci. 9 , art. 645011.

[4] Sánchez‑España et.al. (2020): Degassing Guadiana open pit. Mine Water Environ. 39 (3), 517 – 534.

[5] Schwenk et al. (2022): High temperature noble gas thermometry in Lake Kivu, East Africa, Sci. Total Environ. 837 , art. 155859.