Hydrochemical evaluation of Lower Niger Drainage Area, southeastern Nigeria

Hydrochemical evaluation of parts of Lower Niger Drainage Area was studied. The distribution and concentration of the major ions were assessed. Atomic absorption spectroscopic and spectrophotometric methods were employed in the analyses of chemical species in water, and Piper, Durov and Schoeller diagrams were used in the processing and interpretation of the results. The results of the hydrochemical analysis show the generalized ionic sequence in the study area as K + > Ca 2+ > Na + > Mg 2+ and Mg 2+ > Ca 2+ > Na + > K + in wet season and Cl − > SO 4 2− > HCO 3 − > NO 3 − in dry season, respectively. Two major water types predominate: Ca–Mg–HCO 3 (17.1%) and Na–K–Cl–SO 4 (82.9%). The dominant hydrochemical facies observed include Cl–SO 4 and Ca–Mg–HCO 3 , while Cl–HCO 3 –NO 3 occurs to a lesser degree. The various facies present depict mixing of water from different sources, weathering of carbonates and silicates and ion exchange processes leading to increased concentration of calcium and magnesium ions in relation to sodium and potassium ions. The presence of calcium, chloride and sulphate species indicates the existence of inverse ion exchange. The water in the study area shows variation in the concentration of ionic species with seasons, while the water type is not season dependent.