Hydrochemical evaluation of groundwater quality: a case study from parts of North-Central, Nigeria

Hydrochemical character of groundwater samples from a part of North-Central Nigeria has been investigated to decipher the physicochemical properties, sources of dissolved ions, hydrochemical facies, factors influencing the groundwater chemistry as well as the suitability of the waters for drinking and irrigation purposes. Sixty-seven (67) groundwater samples from hand-dug wells and boreholes were subjected to major ions and heavy metal analyses. The results were further analysed and studied using Pearson’s statistical correlation, ionic ratios and variation plots. The Pearson’s statistical correlation shows that there exists a very strong correlation between water hardness (TH) with Ca2+ (0.99) and Mg2+ (0.91), this indicates that both ions originate from similar sources. The ionic ratio plots of HCO3 and Mg/Na versus Ca/Na; Ca2+  + Mg2+/HCO3−  + SO42−; (Ca2+ + Mg2+) vs total cations (TZ); (Na + K) vs total cations (TZ) revealed that both carbonate dissolution and silicate weathering serve as major contributor of ions to groundwater chemistry in the study area. Piper and Schoeller’s plots revealed that majority of the water samples are of CaHCO3 type, and few NaHCO3 and CaCl2 types. Gibbs plot suggested that chemical weathering of rocks, ionic exchange and secondary carbonates dissolution and precipitation influenced the groundwater chemistry. Comparison of the concentrations of the ions to World Health Organization (WHO) and Standard Organization of Nigeria (SON) showed that they are generally within permissible limits and therefore suitable for drinking purpose. Irrigation parameters such as, electrical conductivity, sodium adsorption ratio, Wilcox ratio, residual sodium carbonate (RSC), sodium solubility percentage (SSP), magnesium ratio/hazard (MR), permeability index (PI), Kelly ratio/index (KI), all revealed that > 90% of water samples fell into suitable, good and excellent water class and are thus generally suitable for irrigation purposes.