Multivariate and Water Quality Index Approaches for Spatial Water Quality Assessment in Lake Ziway, Ethiopian Rift

Information on water quality in aquatic environments is essential for managing and protecting surface water resources, such as lakes, reservoirs, and rivers. This study investigates the spatial status of water quality and the sources of contamination in Lake Ziway, Ethiopian Rift. Evenly distrusted lake water sampling, including the major feeding streams and effluents from floriculture and domestic waste that might have an impact on the lake's water quality, was carried out. For hydrochemical analysis, multivariate techniques and water quality index (WQI) approaches were applied based on 44 water quality parameters. The water quality analysis result showed a non-uniform distribution of the measured physico-chemical and organic matter load indicators across the lake area. Multiple pollutants are present in the lake water at levels that exceed the World Health Organization's recommendations. TU, EC, pH, DO, BOD, COD, Na+, K+, HCO3-, Mn2+, and a few samples for F-, Ni2+, and Pb2+ were the most commonly desecrated. Principal component analysis (PCA) identified four major components with 74.35% cumulative variance, and cluster analysis (CA) resulted in three clusters representing the central, southern, and northern sectors of the lake. The results of PCA and CA indicated that the water quality of the lake is largely controlled by sediments, nutrients, and organic sources as the key lake pollution sources. The overall water quality analysis (WQI > 300) of Lake Ziway and its major feeding rivers is categorized as unsuitable for domestic uses as well as aquatic life. The combined application of multivariate and WQI analysis showed how human-induced activities in the watershed, such as soil erosion, agriculture, industrialization, and urbanization, had a significant impact on the lake water quality and ecological integrity.