Assessment of the Impacts of Climate Variability on Surface Water Quality of Nyabarongo River, Rwanda

The study aimed to investigate the impact of climatic variability on the surface water quality of the Nyabarongo River over the 2019 – 2024 period. The research sought to identify how seasonal changes in rainfall and temperature influence various physicochemical and microbial water quality parameters. Key findings revealed significant seasonal variations in water quality, closely linked to climatic factors. During the rainy seasons, water quality parameters such as nitrate and total coliform counts were notably elevated. For example, average nitrate concentrations were highest during these periods, reaching 132.39 mg/L in March-April-May and 77.33 mg/L in January-February, compared to much lower levels of 15.41 mg/L in June-July-August. Similarly, total coliform counts peaked at 189,597.22 MPN/100 mL in March-April-May and 164,799.08 MPN/100 mL in January-February, while they dropped to 65,537.11 MPN/100 mL in June-July-August. This pattern suggested that increased rainfall leads to higher runoff and potential contamination sources entering the river, adversely affecting microbial water quality. Temperature also played a role in influencing water quality, albeit less dramatically than rainfall. The study noted relatively stable temperature ranges across the seasons, but with slight variations that could affect biological activity in the water. Overall, the findings underscore a clear relationship between climatic variability, specifically rainfall patterns, and the surface water quality of the Nyabarongo River, indicating that periods of heavy rainfall can lead to deteriorating water quality due to increased nutrient loading and contamination. This study recommended the need for effective water quality management strategies, particularly during the rainy season when the river is more susceptible to pollution