Major cations
The order of cation dominance is calcium > magnesium>potassium > sodium in the study area. In a study area, sodium range between 12 to 122 mg/L with an average of 51.4 mg/L. All the sample locations fall under the permissible level of sodium for drinking purposes (Fig.3e). Calcium and magnesium are major cations that are highly influencing the quality of groundwater (Kawo et al., 2018). In a study area, calcium ranges from 20 to 400 mg/L, with an average of 135.93 mg/L. In the spatial analysis, 16.97 sq.km area falls under acceptable, 599.58sq.km area falls under permissible, and 50.40 sq.km area (Fig.3f) falls under the undesirable limit recommended by WHO (2011) and BIS (2012). A concentration of magnesium ion ranges from 6.07 mg/L to 194.4 mg/L, with a mean of 76.14 mg/L. About 3.22 sq.km area is acceptable, 599.46 sq.km area is permissible, and 64.27 sq.km area (Fig.4a) is recorded as an undesirable limit as per standards. An excess concentration of calcium and magnesium causes severe health issues on human and water used for irrigation purposes (Aravinthasamy et al., 2019). Potassium range between 2 to 18 mg/L with a mean of 9.66 mg/L and 26.67 % of the sample locations (Fig.4b) are highly affected due to the presence of higher concentration. The weathering of feldspars, microcline, orthoclase, and biotite are the major mineral causes the excess concentration of potassium in groundwater.