Spatial-Temporal Dynamics in Potable Water Quality: A Case Study of Mizan-Aman Town, Southwest, Ethiopia

Abstract

Surface water is one of the sources of global potable water. However, the quality of surface water has been degrading due to an increase in human activities. Hence, the present study was conducted to evaluate the spatial and temporal variability in drinking water physico-chemical and bacteriological characteristics from the different sources in Mizan-Aman, Ethiopia. The physico-chemical characteristics of water at the Kosokol site were found to be statistically different ( $p<0.05$ ) from the other sites (Gacheb, Tsit, Reservoir 1, and Reservoir 2 sites). The dry and wet season temperature (27.1 and 23.8°C), turbidity (37.4 and 54.8 NTU), pH (7.6 and 8.1), biological oxygen demand (18.1 and 20.7 mg/l), phosphate (2.4 and 3.5 mg/l), and ammonia (2.2 and 4.8 mg/l) of the water were beyond the acceptable limit set for drinking water by both Ethiopian standards (temperature: <15°C; turbidity: 7 NTU; pH: 6.5–8.5; BOD: 10 mg/l; phosphate: 0.02 mg/l; and ammonia: 1.5 mg/l) and the WHO standards (temperature: <15°C; turbidity: 5 NT U; pH: 6.5–8.5; BOD: 5 mg/l; phosphate: 0.01 mg/l; and ammonia: 1.5 mg/l). The total coliform (366.5 and 494.3 CFU/100 ml) and fecal coliform (209.5 and 278.3 CFU/100 ml) contents of the water in the dry and wet seasons are beyond the acceptable limits for drinking water by Ethiopian standards (total and fecal coliform: 0) and the WHO standards (total and fecal coliform: 0). The physico-chemical and bacteriological characteristics of the water in the wet season were found significantly higher than those ( $p<0.05$ ) in the dry season. In general, the water quality changes on a spatial and temporal basis in the study area. Thus, it is important to encourage water quality management works at the upper source sites of the catchment. Furthermore, the city water authority should reinforce safeguarding treatment processes, continuous monitoring of water quality as well as risk assessment and management practices.