Assessing the Water Quality of Lake Hawassa Ethiopia—Trophic State and Suitability for Anthropogenic Uses—Applying Common Water Quality Indices

Abstract

The rapid growth of urbanization, industrialization and poor wastewater management practices have led to an intense water quality impediment in Lake Hawassa Watershed. This study has intended to engage the different water quality indices to categorize the suitability of the water quality of Lake Hawassa Watershed for anthropogenic uses and identify the trophic state of Lake Hawassa. Analysis of physicochemical water quality parameters at selected sites and periods was conducted throughout May 2020 to January 2021 to assess the present status of the Lake Watershed. In total, 19 monitoring sites and 21 physicochemical parameters were selected and analyzed in a laboratory. The Canadian council of ministries of the environment (CCME WQI) and weighted arithmetic (WA WQI) water quality indices have been used to cluster the water quality of Lake Hawassa Watershed and the Carlson trophic state index (TSI) has been employed to identify the trophic state of Lake Hawassa. The water quality is generally categorized as unsuitable for drinking, aquatic life and recreational purposes and it is excellent to unsuitable for irrigation depending on the sampling location and the applied indices. Specifically, in WA WQI, rivers were excellent for agricultural uses and Lake Hawassa was good for agricultural uses. However, the CCME WQI findings showed rivers were good for irrigation but lake Hawassa was marginal for agricultural use. Point sources were impaired for all envisioned purposes. The overall category of Lake Hawassa falls under a eutrophic state since the average TSI was 65.4 and the lake is phosphorous-deficient, having TN:TP of 31.1. The monitored point sources indicate that the city of Hawassa and its numerous industrial discharges are key polluters, requiring a fast and consequent set-up of an efficient wastewater infrastructure, accompanied by a rigorous monitoring of large point sources (e.g., industry, hospitals and hotels). In spite of the various efforts, the recovery of Lake Hawassa may take a long time as it is hydrologically closed. Therefore, to ensure safe drinking water supply, a central supply system according to World Health organization (WHO) standards also for the fringe inhabitants still using lake water is imperative. Introducing riparian buffer zones of vegetation and grasses can support the direct pollution alleviation measures and is helpful to reduce the dispersed pollution coming from the population using latrines. Additionally, integrating aeration systems like pumping atmospheric air into the bottom of the lake using solar energy panels or diffusers are effective mitigation measures that will improve the water quality of the lake. In parallel, the implementation and efficiency control of measures requires coordinated environmental monitoring with dedicated development targets.

Physical and chemical water quality characteristics in six wetlands of Lake Tana, Ethiopia

“…According to (Smith, 1962) blue-green algae (cyanobacteria) had a capacity to dominate in the lake section when the TN:TP ratio was less than 29 and it tends to be rare in the lake when TN:TP > 29. The mean value of the TN:TP ratio was 6.1 ± 10.6, which was lower than the report in Lake Ziway by (Tibebe et al, 2018) (48:1), in Lake Hawass by (Lencha, et al, 2021) (31:1). Even though, there was no signi cant difference in the TN:TP ratio among the six wetlands and among the four seasons, Lake Tana wetlands are hypereutrophic lakes (Downing and McCauley 1992).…”

Impacts of Stressors on Riparian Health Indicators in the Upper and Lower Indus River Basins in Pakistan

“…Published literature indicates that all geographical areas that retain parallel sites are clustered together. Riparian zones underwent significant changes because of human impacts on land-use scenarios [ 53 , 54 , 55 , 56 ], which in turn resulted in significant changes in RHIs. Our findings are consistent with those of other studies examining regions such as the IRB.…”

Estimation of Nutrient Load for Effective Water Resource Management in Dams: A case study of the Roodeplaat Dam, Southern Africa

“…Nutritional loading and microbiological contamination are common in developing countries, whereas industry-derived pollution is typically localized and associated with land use. In Africa, hazardous and insu cient water supply is common and frequently contributes to the burden of communicable diseases (Lencha et al 2021). For instance, major lakes in Africa (e.g., Lake Victoria, Lake Tanganyika, Lake Kariba, and Hartbeespoort Dam) and rivers (Nile, Zambezi, and Orange) experience excessive nutrient loading, which leads to eutrophication (Britton et Njagi et al 2022).…”