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- 2020| ElsevierGroundwater quality and its suitability for drinking and irrigation uses were assessed and multivariate statistical analysis were applied to understand the chemical characteristics of groundwater in the upper part of Luvuvhu sub-catchment in Limpopo, South Africa. The groundwater samples collected during August 2015 (n = 41) and November 2016 (n = 40) were analysed for chemical constituents. The groundwater is fresh and acidic to alkaline in nature. The major hydrochemical facies are Ca–Mg–Cl and Ca–HCO3- in the study area. Groundwater suitability assessment for drinking purposes carried out using World Health Organisation and South African National Standards suggest that groundwater is suitable for drinking without any restrictions. Irrigation suitability assessment suggested that groundwater is suitable for all types of crops and soils. Pearson correlation analysis and principle component analysis (PCA) explains that groundwater chemistry is governed by natural and anthropogenic activities. Hierarchical cluster analysis (HCA) classified wells into three groups (CG1, CG2, CG3). Wells in CG1 and CG2 are less mineralized and are of Ca–Mg–Cl water types. Water chemistry in these wells are affected by recharge process and surface contamination sources. Wells in CG3 are highly mineralized and are of Ca–HCO3 type. Bicarbonate is the dominant anion and water chemistry in CG3 is regulated by silicate and carbonate weathering processes. This study recommends further periodic monitoring to protect aquifers in long run.
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- Impact of irrigation return flow induced mineral weathering and ion exchange reactions in the groundwater was studied in Limpopo region, South Africa. Based on EC (>500) and HCO3 (>150mg/l), groundwater samples are classified into two groups due to its heterogeneous nature. Water types in group 1 and 2 wells are Ca-Mg-Cl-SO4 and Ca-Mg-HCO3, respectively. Gibbs plots, bivariate plots and ionic ratios (Mg/Na vs Ca/Na; HCO3/Na vs Ca/Na; mCa + Mg vs mHCO3; mNa + K vs mHCO3; Ca + Mg-HCO3-SO4 vs Na + K-Cl; mCa + Mg/HCO3 vs Cl; Ca + Mg/SO4 +HCO3 >1; Na/Cl ratio; Cl + SO4 vs HCO3), chloro alkaline indices (CAI, CA2) and Pearson correlation analysis imply that groundwater chemistry is influenced by mineral weathering (carbonate > silicate minerals), reverse ion exchange and irrigation return flow. In group 1 wells, Cl + SO4 and HCO3 have strong positive correlation and both increases together, suggesting induced mineral weathering caused by nitrification and wastewater infiltration from the surface. Group 2 wells are generally deep with low groundwater level fluctuation and high concentration of major ions. Overall, water chemistry in the group 1 wells is highly affected by the contamination sources than group 2 wells.
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