Abstract
Lake Hawassa is one of the major Ethiopian Rift Valley Lakes having an endorheic basin system. The surrounding community makes use of the lake water for the multiple purposes of irrigation, domestic water supply, recreation and fish harvesting. The aim of the present study was to ascertain the water quality of the lake in terms of water quality indices (WQI) and its health over a period of three months covering both dry and wet seasons. Overall, the water quality of Lake was unfit and bad as per the weighted arithmetic method (120.06–228.29) and modified Bascarón water quality index (MBWQI) methods (26.81–33.89), respectively. However, the quality was indicated as marginal, as per the Canadian Council of Ministers of the Environment (CCME) water quality index method (44.2–51.1). On average, the lake was under the hypertrophic stage as per the standard based on the results of Secchi depth and nutrient concentration. The current study showed the lake being unfit for all-purposes as per WAWQI range (> 100). According to the physicochemical and biological parameters, of the lake, it requires mitigation measures to control Eutrophication and pollutants inflow.
Highlights
Surface water sources have a high vulnerability to pollution than groundwater resources
The water quality index for the river was calculated from eleven parameters, namely: BOD, Total dissolved solids (TDS), pH, dissolved oxygen (DO), turbidity, PO4, NO3, chlorides, TH, EC, and alkalinity for eleven sampling stations to assess the suitability of lake water for general purposes
Turbidity values of three points (S3, S7 and S8) and DO values of four points (S1, S5, S6 and S9) out of eleven sampling points were below the permissible limit of WHO standards
Summary
Surface water sources have a high vulnerability to pollution than groundwater resources. The lakes are exceptionally exposed to pollution due to their size and proximity to the community compared to the ocean or sea and rivers. The plodding accumulation of sediment and organic matter modify the features of the lake such as depth, biological productivity, oxygen levels, and water clarity over a period of time (Steinberger et al 2019). Anthropogenic actions and natural phenomena trigger rapid environmental changes in the lakes which are the most fragile in nature (Abebe Yonas et al, 2018). Human intervention has significant effects on lake water quality due to discharge of domestic, industrial, urban and agricultural wastewaters into the water courses (whether intentional or accidental).
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