Hydrochemistry and Water Quality Index of groundwater resources in Enugu north district, Enugu, Nigeria Nwachukwu R. Ekere & Vitus E. Agbazue & Benedict U. Ngang & Janefrances N. Ihedioha Received: 23 January 2018 /Accepted: 28 January 2019 # Springer Nature Switzerland AG 2019 Abstract The physicochemical parameters of groundwater in 12 cluster boreholes in Enugu North district/region, southeast Nigeria, were studied. Twelve physicochemical parameters were determined in triplicates at monthly intervals for 3 months in dry season and then repeated in rainy season in 120 boreholes grouped into 12 clusters for 2 years. The range of values obtained during dry season include phosphate (0.12–0.87 mg/L), nitrate (1.24–8.72 mg/ L), sulfate (20.10–24.34 mg/L), pH (4.9–7.5), E.C. (10.0–410.0 μS/cm), total acidity (0.06–1.24 mg/L), total alkalinity (28.0–22.10 mg/L), total hardness (100.0–140.1 mg/L), TSS (70.0–270.0 mg/L), TDS (0.00–210.0 mg/L), TS (70.0–390.0 mg/L), and tur- bidity (3.4–50.0 mg/L) while rainy season values were phosphate (0.30–10.60 mg/L), nitrate (1.20– 120.0 mg/L), sulfate (0.0–100.0 mg/L), pH (4.9– 7.5), E.C. (10.0–360.0 μS/cm), total acidity (0.10– 10.5 mg/L), total alkalinity (10.0–52.1 mg/L), total hardness (100–130 mg/L), TSS (100.0–280.0 mg/L), TDS (0.0–260.0 mg/L), TS (110.0–560.0 mg/L), and turbidity (3.80–56.0 mg/L). When compared with standard guideline values recommended by regulato- ry bodies, rainy season nitrate values in some sam- ples and phosphate mean values were higher than recommended values. Seasonal variations of the parameters in the samples were observed. Statistical analysis showed statistically significant variations between the 12 borehole water physicochemical pa- rameters in dry and rainy seasons. Water quality index (WQI) analysis categorized all the water sam- ples within the range of good to excellent. Keywords Groundwater . Monitoring . Hydrochemistry . Nitrate . District . Water supply Introduction Over a billion people worldwide do not have access to safe drinking water, and only a small world popu- lation has access to good quality water (UNICEF 2010). Early warning reports by United Nation Envi- ronment Programme (UNEP) revealed that some 25 million people die yearly due to consumption of polluted water (Morris et al. 2003). United Nations Report indicated that water-borne diseases are en- demic in certain parts of Nigeria, Africa’ s most pop- ulous country (UNESCO 2006). UNICEF empha- sizes that the occurrence of certain major childhood killer diseases in Nigeria could decline by 15% if water quality was improved (Adoga 2006). It has been established that more than half of the world’ s large modern cities, smaller towns, and rural communities depend on groundwater supply for domes- tic use, and this has often been attributed to its relative cheapness, safety, and reduced vulnerability to pollution (Morris et al. 2003; British Geological Survey 2003; Environ Monit Assess (2019) 191:150 https://doi.org/10.1007/s10661-019-7271-0 N. R. Ekere (*) : V. E. Agbazue : B. U. Ngang : J. N. Ihedioha Analytical/Environmental Chemistry Laboratory, Department of Pure and Industrial Chemistry, University of Nigeria, Nsukka, Nigeria e-mail: nwachukwu.ekere@unn.edu.ng