Morphometric Characteristics and Hydrology of Selected Ethiopian Rift Lakes

Abstract

In the Main Ethiopian Rift (MER), intra-rift faulting and associated volcanic activities resulted in the formation of volcano-tectonic structural depressions, responsible for the formation of many lakes on the rift floor. These lakes are bordered to the east and west by elevated highlands where the main tributary feeder rivers originate. The MER is occupied by seven major lakes, namely, from south to north, Chamo, Abaya, Awasa, Shala, Abijata, Langano, and Ziway. Most of these lakes are closed basins and interconnected by groundwater, through a NE–SW-aligned regional fault system, whereas Abijata Lake receives surface water from Ziway and Lagano lakes by two small streams. The geomorphic characteristics and size of these lakes changed on time scales of decades to millennia in response to different factors such as volcanic activity, tectonics, climate change and, very recently, human impact (mainly water withdrawal, deforestation, and irrigation). The most prominent example is the dramatic change of Abijata, the size of which decreased dramatically in the last decades.