The Ethiopian rift is known for its diverse landscape, ranging from arid and semi-arid savannahs to high and humid mountainous regions. Lacustrine sediments and paleo-shorelines indicate water availability fluctuated dramatically from deep fresh water lakes, to shallow highly alkaline lakes, to completely desiccated lakes. To investigate the role lakes have played through time as readily available water sources to humans, an enhanced knowledge of the pace, character and magnitude of these changes is essential. Hydro-balance models are used to calculate paleo-precipitation rates and the potential pace of lake level changes. However, previous models did not consider changes in hydrological connectivity during humid periods in the rift system, which may have led to an overestimation of paleo-precipitation rates. Here we present a comprehensive hydro-balance modeling approach that simulates multiple rift lakes from the southern Ethiopian Rift (lakes Abaya, Chamo, and paleo-lake Chew Bahir) simultaneously, considering their temporal hydrological connectivity during high stands of the African Humid Period (AHP, ~15–5 ka). We further used the Surface Energy Balance Algorithm for Land (SEBAL) to calculate the evaporation of paleo-lake Chew Bahir's catchment. We also considered the possibility of an additional rainy season during the AHP as previously suggested by numerous studies. The results suggest that an increase in precipitation of 20–30% throughout the southern Ethiopian Rift is necessary to fill paleo-lake Chew Bahir to its overflow level. Furthermore, it was demonstrated that paleo-lake Chew Bahir was highly dependent on the water supply from the upper lakes Abaya and Chamo and dries out within ~40 years if the hydrological connection is cut off and the precipitation amount decreases to present day conditions. Several of such rapid lake level fluctuations, from a freshwater to a saline lake, might have occurred during the termination of the AHP, when humid conditions were less stable. Fast changes in fresh water availability requires high adaptability for humans living in the area and might have exerted severe environmental stress on humans in a sub-generational timescale.

埃塞俄比亚的裂谷以其多样的景观而闻名，从干旱和半干旱的大草原到高湿的山区。Lacustrine沉积物和古海岸线表明，水的供应量从深水淡水湖到浅度高碱性湖水，再到完全干燥的湖水，波动很大。为了调查湖泊作为人类随时可用的水源在一段时间内所扮演的角色，必须增强对这些变化的速度，特征和大小的了解。水力平衡模型用于计算古降水率和湖泊水位变化的潜在速度。但是，以前的模型没有考虑裂谷系统在潮湿时期水文连通性的变化，这可能导致对古降水率的高估。在这里，我们考虑到非洲湿润时期（AHP）高峰期的时间水文连通性，提出了一种综合的水力平衡建模方法，该方法可以同时模拟来自埃塞俄比亚南部大裂谷（湖Abaya，Chamo和古湖Chew Bahir）的多个裂谷，〜15–5 ka）。我们还使用了土地表面能平衡算法（SEBAL）来计算古湖Chew Bahir流域的蒸发量。正如许多研究先前所建议的那样，我们还考虑了在AHP期间可能会有额外的雨季的可能性。结果表明，在整个埃塞俄比亚大裂谷，降水量增加20％至30％才能使古湖Chew Bahir达到其溢流水平。此外，结果表明，古湖Chew Bahir高度依赖于上层湖泊Abaya和Chamo的水供应，如果切断水文联系并且降水量减少到今天，则在约40年内会变干。在AHP终止期间，湿度条件不稳定时，可能发生了从淡水到盐湖的一些此类湖水位快速波动。淡水供应的快速变化要求对居住在该地区的人类具有高度适应性，并且可能在次世代的时间尺度上对人类造成严重的环境压力。当潮湿条件不稳定时，AHP终止期间可能发生了从淡水到盐湖的逆流。淡水供应的快速变化要求对居住在该地区的人类具有高度适应性，并可能在次世代的时间尺度上对人类造成严重的环境压力。当潮湿条件不稳定时，AHP终止期间可能发生了从淡水到盐湖的逆流。淡水供应的快速变化要求对居住在该地区的人类具有高度适应性，并且可能在次世代的时间尺度上对人类造成严重的环境压力。