Spatial-Temporal Analysis of Physicochemical Parameters of Three Ethiopian Rift Valley Lakes Indicating Threats in Ecological Sustainability

Abstract

The Ethiopian Rift Valley lakes provide substantial economic, environmental and social benefits across diverse ecological settings. Sustainability of these benefits is affected substantially by the mega-environmental level climate change and cumulative anthropogenic effects at the lakes and in their catchments landscapes. To provide an insight on some of the challenges that affect the lakes' health, this study assessed major water physicochemical status of three Rift Valley lakes: namely, Chamo, Koka and Ziway and compared with previous data. The water physicochemical data were measured in-situ for two years, i.e., from May 2018 to April 2020. Nutrients loading to the lakes were analyzed from water samples. The study demonstrated that water temperature, pH, electric conductivity (EC), total dissolved solids (TDS), salinity and total phosphorus (TP) varied significantly between seasons within and between the lakes. The findings demonstrated that the EC and TDS levels during the period of this study were higher than previous reported levels. The findings also showed that establishment and invasion of water hyacinth ( Eichhornia crassipes ) weed had association with nutrient loading into the lakes and vegetation in the lake's shore. The very likely anthropogenic effects associated factors including water turbidity, soluble reactive phosphorus, and nitrate-N concentrations varied among the lakes, across seasons and time. Our findings indicate that the urgent need of education and participatory intervention of watershed management, proper agricultural practices, strict and enforced municipal and industrial waste management practices, protection of wetlands vegetation and delimitation of the lakes' buffer zones to sustain the services of the lakes. Keywords : Chamo, Koka, nutrient pollution; water hyacinth, Ziway DOI: 10.7176/JEES/12-9-02 Publication date: September 30 th 2022