Principal component analysis (PCA)
SPSS 21.0 version was used to carry out the principle component analysis of groundwater in the study area. The result of PCA shows that more significant water quality parameters to deteriorate the natural characteristics of groundwater. The varimax method was adopted to rotate the parameters in PCA and extraction limitation of the eigen value greater than one (Pande et al., 2019, Paul et al., 2019). In the study region, PCA illustrates four factors responsible for the data structure (Fig.16a and Table.8), with 76.635 % of cumulative variance. Factor 1 comprises of 49.902% of total variance with high loadings for EC, TDS, TH, Ca2+, Mg2+, SO42- and NO3- (Fig.16b). It represents the anthropogenic activities such as disposal of waste from residents, sewage intrusion; chemical synthetic fertilizers used for high crop yield are the major reason for the excess concentration of salt and other ions.
Factor 2 responsible for 9.618% of total variance with high factor loadings for pH, HCO3-, weak positive loadings of EC, TDS, Na+, Mg2+, and SO42-. It shows that the high value of hydrogen ions is due to weathering of parent rock, rock water interaction, and ion exchange process. These are highly influencing factor in the degradation of groundwater quality. Factor 3 comprises a total variance of 8.739% with high factor loadings of K+, CO32- and weak positive loading of HCO3-. It indicates that potassium-rich minerals such as feldspars, calcite, and dolomite weathering are the major reasons. In specifically, farmers are used 15.5% of nitrogen, and 18.8% of calcium content and easily water-soluble fertilizers are widely used in the study area. The impact of these kinds of fertilizers are initially enhanced the growth of the plant in two to three weeks and gets dissolved into water, finally leachates are diluted with the groundwater. In Factor 4, total variance is 8.376% with high loadings factor of sodium and chloride ions. Due to the action of the ion exchange process, rock water interaction and anthropogenic activities are highly affecting the quality of groundwater in the study region (Fig.16c).