Lake surface area expansion: Insights into the role of volcano-tectonic processes, Lake Beseka, East Africa
Esayas Gebremichael, Wondwosen M. Seyoum, Benite Ishimwe, Guzalay Sataer
Abstract
Lake Beseka, Ethiopia Lake Beseka has been expanding despite climatic and other relevant variables remaining largely the same over time. In this study, we applied an integrated approach based on multi-source datasets—Synthetic Aperture Radar (SAR), Landsat thermal band data, precipitation, and physicochemical and isotope water quality data—to understand the processes that govern the lake surface area expansion with a focus on the volcano-tectonic process. Our findings show the following: (1) overall annual rainfall trend showed a declining trend, suggesting that rainfall is not the main source of water that led to the expansion of the lake; (2) recent vertical deformation rates reveal high subsidence rates on areas bordering the lake to the north, west, and southwest that are dissected by an echelon of fissures and faults, and physicochemical and isotopic water quality analysis from previous studies reveal dilution of the lake water by a new source of water in these parts; and (3) the thermal data analysis showed high land surface temperature values to the north of the lake, where a recent swarm of earthquakes were detected. We attributed the lake surface area growth to two processes: groundwater influx into the lake surface facilitated by active volcano-tectonic processes and volcano-tectonic-induced subsidence that creates favorable conditions for the water to expand to new areas.