Mapping of Groundwater Chemistry and Hydrochemical Facies of Part of Minna, North Central, Nigeria.

Hydrochemical patterns has been mapped and correlated with groundwater flow systems to varying degrees using hydrochemical facies. Reliable broad relationship between chemical composition and the flow distribution of groundwater were established in the process. This study examines the water quality and groundwater flow patterns present in the crystalline basement aquifer of Part of Minna in North Central Nigeria for environmental purpose. Sixteen water samples were collected from wells and analyzed for various parameters including pH, total dissolved solids (TDS), electrical conductivity (Ec), K+, Na+, Ca+, Mg+, Cl-, HCO3- and SO4- using standard procedures of water analysis. The analytical results present the abundance of both physical and chemical parameters in the following order: pH (5.8 – 7.6), Ec (116.7 - 1562µs/m), TDS (128.6 – 1046.5 mg/l), Na+ (25.3 – 144.8 mg/l), K+ (1.1 – 39.5 mg/l), Mg+2 (5.6 – 30.7 mg/l), Cl- (20.4 – 276.5 mg/l), HCO3- (10.0 – 21.0 mg/l), SO4- (8.0 – 180 mg/l). Piper trilinear for the study area shows that there is a mixture of two types of water with variable concentrations of major ions. These are Na+ , K– ,Cl– , SO4+2 water type and Ca+ , Mg+2 ,  Cl –, SO4 +2, water types. This means that groundwater in the area is mainly made up of mixtures of the alkaline and alkaline earth metals and predominantly Cl- - SO4+2 water type. Comparison made from the geochemical maps indicate that high total dissolve solids occur at the discharge area and relatively the groundwater at various discharge point is older in age and has high residence time to that of recharge area. Hydrochemical data analysis revealed four sources of solutes. The processes responsible for their enrichment include: chemical weathering, leaching of the overlying sediments, domestic activities, climatic condition and the flow pattern of the aquifer. These factors have contributed to the changes of the groundwater chemistry. From the static well level measurement plot, it was revealed that the dominant trend for the groundwater movement is in the N-S, NW-SE and NE-SW directions which shows that the groundwater of the area is structurally controlled.