Spatiotemporal Assessment of Pollution Levels in the Southern Gulf of Lake Tana

Abstract

This study investigates the spatial and seasonal patterns of pollution in the southern Gulf of Lake Tana, Ethiopia. Lake Tana plays a crucial role in supporting aquatic biodiversity and supplying water to surrounding communities; however, escalating human activities have raised concerns about its water quality. Through systematic sampling and analysis, the study assesses the distribution of pollutants and their seasonal and spatial variability. An integrated methodological framework combining GIS, remote sensing, and physicochemical water quality assessment was employed to provide a comprehensive understanding of pollution dynamics. The results show that dissolved oxygen concentrations recorded mean values ranging from 8.21 to 9.52 mg/L during both dry and wet seasons. Mean total dissolved solids ranged from 97.32 to 99.75 mg/L in the dry season and from 97.81 to 104.02 mg/L in the wet season, revealing a decreasing trend from near shore reference points toward the open lake with increasing horizontal distance. In contrast, turbidity values increased horizontally, rising from an average of 11.48 to 16.43 NTU. Phosphate concentrations exhibited marked seasonal and spatial variability, with mean values ranging from 9.43 to 9.53 mg/L in the dry season and from 0.64 to 1.22 mg/L in the wet season, indicating significant differences among sampling stations. Overall, the study demonstrates that the physicochemical characteristics of Lake Tana vary both spatially and seasonally, particularly in areas adjacent to the shoreline near Bahir Dar City, highlighting clear evidence of pollution impacts within the lake.

Keywords: Physicochemical parameters, Spatio-temporal variations, GIS, Lake Tana, pollution