Seasonal assessment of microbiological and physicochemical water quality in Lake Tana: Implications for drinking water in island communities

Surface water is one of the common drinking water sources used by many people in low- and middle-income countries. In Ethiopia, individuals living around Lake Tana, particularly those on the islands, consume water directly from the lake despite the risk of contamination. This study characterizes the water quality of the lake to assess its suitability for drinking for the island communities. Samples from the lake, taken near the islands, were analyzed for fecal coliform and physicochemical parameters, including pH, temperature, electrical conductivity, total dissolved solids, turbidity, nitrate, ammonia, phosphate, total alkalinity, total hardness, sulfate, and fluoride during both wet and dry seasons. The wet season water quality analysis was conducted in August 2024, while the dry season analysis took place in January 2025. The results indicated that the lake is highly contaminated with fecal coliform and affected by turbidity, with the degree of contamination worsening in the wet season. The maximum fecal coliform count in the wet season was greater than 2000 CFU/100 mL. None of the samples met the fecal coliform drinking water quality standard in the wet season; the majorities were classified under the high-risk category. In the dry season, the maximum fecal coliform count was 420 CFU/100 mL, with only 23.5% of samples categorized as conforming. The maximum turbidity was 92.7 NTU in the wet season and 30.7 NTU in the dry season, with all samples in the wet season and 94.2% in the dry season remaining unacceptable for drinking. These results indicate insufficient access to clean water, undermining the achievement of SDG 6, and they also compromise the health and wellbeing of people, undermining the achievement of SDG 3. Other physicochemical parameters, however, were within guideline limits. The findings highlight the urgent need for implementing household level or community scale treatment facilities to ensure safe drinking water and enhance the public health.