Assessment of Nutrient Concentration in Sokori River, Southwest Nigeria

Water management planners are facing considerable uncertainties on future demand and availability of water partly due to concentration of nutrient leading to excessive unsightly growth of aquatic plants and algal bloom in rivers. This study was carried out to assess the trend of nutrient concentration in Sokori stream in Southwest Nigeria. The selected nutrients determined in the stream were nitrate, sulphate and phosphate, dissolved oxygen and biological oxygen demand. Water samples from 10 sampling point at 100m interval were examined to assess the variation in concentration of nutrients along the stream using standard method. Descriptive statistics was used in data analysis. The result showed that high nutrient concentrations were established at the middle section of the stream. It is obvious that sulphate has the highest concentration (3.60 Mg/l), followed by phosphate (2.13 Mg/l) then nitrate (0.89 Mg/l). However, the nutrient concentrations in the stream were below the acceptable limit set by the World Health Organization. Furthermore, it was observed that where the nutrients concentration (PO₄ = 5.16 Mg/l, SO₄,= 9.78 Mg/l, NO₂ = 1.46 Mg/l) and the BOD₅ (10.24 Mg/l) were highest at the mid – section of stream, while the DO concentration (3.63 Mg/l) lowest indicating concentrated aquatic life (macro and micro-organisms) activity. Nutrient enrichment leads to excessive growth of primary producers as well as heterotrophic bacteria and fungi, which increases the metabolic activities of stream water leading to a depletion of dissolved oxygen. The low discharge of stream and its fairly flat terrain nature also influenced the metabolic activities in the mid- section of the stream although there was no evidence of accumulation of nutrient leading to eutrophication risk.