title: Characterisation of the subaquatic groundwater discharge that maintains the permanent stratification within Lake Kivu; East Africa.
abstract: Warm and cold subaquatic groundwater discharge into Lake Kivu forms the large-scale density gradients presently observed in the lake. This structure is pertinent to maintaining the stratification that locks the high volume of gases in the deepwater. Our research presents the first characterisation of these inflows. Temperature and conductivity profiling was conducted from January 2010 to March 2013 to map the locations of groundwater discharge. Water samples were obtained within the lake at the locations of the greatest temperature anomalies observed from the background lake-profile. The isotopic and chemical signatures of the groundwater were applied to assess how these inflows contribute to the overall stratification. It is inferred that Lake Kivu's deepwater has not been completely recharged by the groundwater inflows since its turnover that is speculated to have occurred within the last ~1000 yrs. Given a recent salinity increase in the lake constrained to within months of seismic activity measured beneath the basin, it is plausible that increased hydrothermal-groundwater inflows into the deep basin are correlated with episodic geologic events. These results invalidate the simple two-component end-member mixing regime that has been postulated up to now, and indicate the importance of monitoring this potentially explosive lake.
authors: Department of Surface Waters - Research and Management, Eawag: Swiss Federal Institute of Aquatic Science and Technology, Kastanienbaum, Switzerland; Institute of Biogeochemistry and Pollutant Dynamics, ETH: Swiss Federal Institute of Technology, Zurich, Switzerland.
authors: Kelly Ann
authors: KA
authors: Ross
authors: Department of Chemistry, UR-CST: University of Rwanda, College of Science and Technology, Kigali, Rwanda.
authors: Elisée
authors: E
authors: Gashugi
authors: Department of Chemistry, UR-CST: University of Rwanda, College of Science and Technology, Kigali, Rwanda.
authors: Augustin
authors: A
authors: Gafasi
authors: Department of Surface Waters - Research and Management, Eawag: Swiss Federal Institute of Aquatic Science and Technology, Kastanienbaum, Switzerland; Laboratory of Physics of Aquatic Systems, EPFL: École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
authors: Alfred
authors: A
authors: Wüest
authors: Department of Surface Waters - Research and Management, Eawag: Swiss Federal Institute of Aquatic Science and Technology, Kastanienbaum, Switzerland.
authors: Martin
authors: M
authors: Schmid
mesh_terms: D000351:Africa, Eastern; D055866:Earthquakes; D060587:Groundwater; D060106:Lakes; D013696:Temperature