Comparative Assessment of the Water Quality Deterioration of Ethiopian Rift Lakes: The Case of Lakes Ziway and Hawassa

Abstract

The Ethiopian Rift Valley Lakes Basin consists of chain of lakes, many feeder streams and wetlands with unique hydrological and ecological characteristics having regional and global environmental importance. With growing population and consequent various human activities and degradation of watersheds aggravated by climatic change, the water quality of rivers and lakes and feeder rivers are deteriorating fast. The purpose of this study is to assess physicochemical water quality parameters in two of relatively fresh water lakes (Ziway and Hawassa) which are occupying in the Central Main Ethiopian Rift floor. These parameters are pH, dissolved oxygen (DO), total dissolved solids (TDS), turbidity (NTU), Electrical conductivity (EC), and fluoride ion concentration(F -). The mean values of those physico-chemical parameters were compared with maximum permissible limit (MPL) for drinking water as standardized by the Ethiopian Ministry of Health (MoH) and the World Health Organization (WHO). The result revealed that most of the parameters show clear deterioration over the last few decades. The likely factors are rapid urbanization, sedimentation, excessive use of fertilizers and industrialization in towns established along their shorelines. Hence, these trends demand immediate intervention to avert the grave environmental consequences.