Evaluating the impact of flood events on the water quality of Ethiope River: A comparative study of wet and dry seasons

Abstract

The quality of water in the Ethiope River was assessed across three stations to evaluate the impacts of flooding and anthropogenic pollution. Physico-chemical parameters including pH, dissolved oxygen (DO), biochemical oxygen demand (BOD), electrical conductivity (EC), total dissolved solids (TDS), nitrate, phosphate, and heavy metals were measured. Station 1, located upstream, exhibited minimal contamination, with water quality parameters largely within WHO (2011) guidelines, reflecting a relatively pristine environment. In contrast, Station 2, situated at the flood discharge point, showed significant pollution, marked by elevated BOD, nitrate, phosphate, and EC, indicative of contamination from agricultural runoff and urban wastewater. The Water Quality Index (WQI) at Station 2 was the highest, highlighting severe water quality degradation. Station 3, downstream, displayed partial recovery, with improved BOD and EC levels, although phosphate and nitrate concentrations remained elevated. The seasonal variation in water quality was significant (P<0.05), with wetter conditions exacerbating nutrient loading and organic matter input, while the dry season showed some attenuation. These findings suggest that the Ethiope River is subjected to both natural and anthropogenic stressors, with flood events intensifying pollution levels, especially at Station 2. The river’s ability to self-purify downstream was evident, though continuous pollution sources upstream led to ongoing contamination. This study contributes to understanding the impact of flooding and pollution on water quality in tropical rivers, providing insights into the resilience and challenges faced by river ecosystems in flood-prone regions.