Seasonal Variability of Water Quality in the Zigi River, Northern Tanzania
Water quality parameters (colour, total suspended solids (TSS), turbidity, electrical conductivity (EC), pH, dissolved oxygen (DO), total dissolved solids (TDS), temperature, nitrate, phosphate and faecal coliforms) were evaluated during wet and dry seasons in relation to human activities in Zigi River and its tributaries. Samples were taken from nine strategic sampling points located in different areas of river. The samples were processed and analysed using established procedures. Results of temperature, EC, TDS, TSS, nitrate, colour, turbidity and E. coli were higher in wet season than in dry season. Significant variations (p < 0.05) of temperature, EC, TDS, nitrates, colour and turbidity with changing seasons were observed. Also, results on variations of other parameters were more or less the same in both seasons. Temperature, EC, TDS, nitrate and E. coli were increasing and DO decreasing downstream in both seasons probably due to increased anthropogenic activities along the river. High Pearson correlation coefficient (r2 > 0.53) observed between these parameters indicated that these values are closely related. Results of assessment of water using water quality index have revealed that the river water in both seasons is unsuitable for use as drinking water and that the water is more unsuitable for use during the wet season than during the dry season. Implications of the findings on water treatment are vivid and immediate measures are recommended to minimise the further diminishing quality of the water in this river and thus reduce the costs of treating the water for domestic use.