Seasonal Variations in Surface Water Quality in River Njoro and Lake Nakuru, Kenya

Abstract

Water pollution from rivers and lakes has resulted in serious environmental issues on a global scale. The public's growing concern over the decline in river and lake water quality makes it more important than ever to assess the water quality of these bodies of water over a prolonged period of time. During the rainy and dry seasons of 2022, 120 water samples were collected from 5 monitoring stations located within River Njoro and Lake Nakuru. The samples underwent physicochemical analysis of selected water parameters, which included salinity, temperature, pH, turbidity, total nitrogen (TN), total phosphorus (TP), electric conductivity (EC), and total dissolved solids (TDS). The results were compared using the National Environmental Management Authority (NEMA) of Kenya's guidelines and the results showed that the water quality of the Njoro river and Lake Nakuru fluctuated with the seasons, particularly in the lower water column of river Njoro. The quality parameters had the following values; EC values range between 73.33 ± 0.55 μs/cm - 533.33 ± 0.64 - μs/cm, respectively for both seasons; Salinity values range from 0.085 ± 0.02 ppt - 2.59 ± 0.03 ppt; pH values were between 8.8 – 9.3; Temperature was 23.69 ± 0.07 °C – 14.22± 0.07°C; Turbidity varied significantly – 13.95 ± 0.27 NTU - 36.03 ± 0.35 NTU;  TDS between 46.67 ± 0.11 ppm- 243.33 ± 0.04 ppm; TN ranges between 5.97 ± 3.24 mg/L - 8.57 ± 3.18 mg/L and TP 7.49 ± 1.7-9.41 ± 1.84 mg/L in the dry and rainy seasons, for River Njoro and Lake Nakuru respectively. This study showed that the degree to which human activity affects water quality varies with the season. Therefore, most of these factors should be considered while controlling rivers downstream in order to ensure the health of aquatic life, also it is essential to increase lake water quality monitoring and regulate human activity. Additionally, the results revealed that water pollution resulted primarily from domestic wastewater, agricultural runoff and industrial effluents.