Downstream variation in the surface water quality of an urbanizing sub-catchment in Ibadan, Nigeria

Abstract

Contamination of surface water bodies from various human activities significantly impairs environmental health and the well-being of humans, plants and animals. This study seeks to assess the variation downstream in surface water characteristics in a small urbanizing sub-catchment in Ibadan, Nigeria. Water sampling was carried out on the 14 first-order, 4 second-order and 5 third-order stream networks of the sub-catchment. The concentration of pH, total dissolved solids (TDS), alkalinity, total hardness, calcium and magnesium were determined in relation to stream order and increased distance downstream. The values range considerably across the sub-catchment; pH (3.8-7.5), TDS (70-1095 ppm), alkalinity (0.65-4.65 ml), total hardness (2.35-36.95 ml), calcium (1.6-35.35 mg/l) and magnesium (0.05-14.70 mg/l). Statistical analysis shows that there is no significant correlation between the concentration of the water quality parameters, stream order and distance downstream. This however suggests that pollutants infiltrate and sink at different random points along the stream channels to contaminate the subsurface layers and subsequently the groundwater system. Based on the result of this study, the level of pollution for the selected parameters has not attained a critical level, however, there is a need to put in place an effective water quality monitoring scheme to control further pollution.