Assessment of spatio-temporal variations of selected water quality parameters of Lake Ziway, Ethiopia using multivariate techniques

Abstract

Excess agrochemicals input from agricultural activities and industrial effluent around Lake Ziway catchment can pose a serious threat on the lake ecosystem. Lake Ziway is a shallow freshwater lake found in the northern part of the Ethiopian Rift Valley. It is characterized as semi-arid to sub-humid type of climate. Expansions of the flower industry, widespread fisheries, intensive agricultural activities, fast population growth lead to deterioration of water quality and depletion of aquatic biota. The spatial and temporal variations of selected water quality parameters were evaluated using multivariate techniques. The data were collected from nine sampling stations during dry and wet seasonal basis for analysis of fifteen water quality parameters. The physicochemical parameters were measured in-situ with portable multimeter and nutrients were determined by following the standard procedures outlined in the American Public Health Association using UV/Visible spectrophotometer. Mean nutrient concentrations showed increasing trend in all seasons. These sites were also characterized by high electrical conductivity and total dissolved solid (TDS). All the nine sampling sites were categorized into three pollution levels according to their water quality features using cluster analysis (CA). Accordingly, sampling sites Fb and Ketar River (Kb) are highly and moderately polluted in both seasons, respectively. On the other hand, sampling sites at the center (C), Meki river mouth (Ma), Ketar river mouth (Ka), Meki River (Mb), Korekonch (Ko) and Fa in dry season and Ka, C, Ma, Ko, Bulbula river mouth (B) and Fa during wet season were less polluted. Principal component analysis (PCA) analysis also showed the pollutant sources were mainly from Fb during dry season Mb and Kb during wet season. The values of comprehensive pollution index illustrated the lake is moderately and slightly polluted in dry and wet seasons, respectively. Comparatively, the pollution status of the lake is high around floriculture effluent discharge site and at the two feeding rivers (Kb and Mb) due to increasing trends in agrochemical loads. In order to stop further deterioration of the lake water quality and to eventually restore the beneficial uses of the lake, management of agrochemicals in the lake catchments should be given urgent priority.

The impact of sewage effluents on water quality of Lake Hawassa, Ethiopia

“…Hierarchical agglomerative clustering is the most common approach, which provides intuitive similarity relationships between any one sample and the entire data set and is typically illustrated by a dendrogram. The dendrogram provides a visual summary of the clustering processes, presenting a picture of the groups and their proximity with a dramatic reduction in dimensionality of the original [ 24 ].…”

“…This technique was applied to recapitulate the statistical correlation among water quality parameters. The water quality parameter was consistent before PCA the analysis was performed in order to minimize the effect of different variables and their respective units of measurements [ 24 ].…”

“…Consequently, to minimize the effect of pollution through appropriate management strategy and legislation, determining the water quality of the lake is critical. This enhances evidence-based decision to ensure the sustainability of the lake and its ecosystem [ 17 , 18 , 24 ]. As a consequence, water pollution is currently a major environmental challenge at Lake Hawassa.…”

“…As a consequence, water pollution is currently a major environmental challenge at Lake Hawassa. Hence, multivariate statistical techniques have been widely adopted to analyze and evaluate surface and freshwater water quality, and are useful to verify temporal and spatial variations caused by natural and anthropogenic factors linked to seasonality [ 22 – 24 ]. Although the numerous management challenges, the multivariate techniques have a limited usage in the assessment of water quality in many lakes in developing countries including Lake Hawassa.…”

Assessments of physico-chemical parameters, nutrient load and trace metal levels in spring and river water using multivariate statistical methods, South Gondar Zone, Ethiopia

“…Water is the most important wealth with its quality and it is a vital to the survival of all living organisms. Pollution of freshwater with potential contaminants due to natural phenomena and anthropogenic activities are of great concern worldwide (Dessie et al, 2022). Water bodies such as river are subjected to pollution mainly through human activities, which affects the properties of water bodies biologically, physically and chemically (Joseph A. et al, 2022).…”