## 3 Results and Discussion
### Multivariate Statistical Analysis  
Figure 8 shows the Pearson correlations between the groundwater quality parameters. Pearson correlation coefficient (\(r\)) ranges from \(-1\) to \(+1\) and measures the strength of the linear relationship between parameters [9]. A high negative correlation is found when \(r\) is close to \(-1\) but \(r\) values close to \(+1\) indicate a high positive correlation. A Pearson correlation (\(r\)) close to 0 indicates that there is no linear relationship between the two variables. \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Parameter**} & **Site (Spatial)** & **Year (Temporal)** \\ \cline{2-3}  & \(p\)**-Value** & \(p\)**-Value** \\ \hline Bicarbonates (mg/L) & 0.0000 * & 0.7058 \\ Fecal coliforms NMP/100 mL & 0.2229 & 0.8342 \\ Total organic carbon (mg/L) & 0.3044 & 0.1937 \\ Ammonium (mg/L) & 0.3219 & 0.4469 \\ Nitrites (mg/L) & 0.7001 & 0.4622 \\ Nitrates (mg/L) & 0.0000 * & 0.0911 \\ Organic Nitrogen (mg/L) & 0.1192 & 0.1272 \\ Total nitrogen (mg/L) & 0.0000 * & 0.1061 \\ Total phosphorus (mg/L) & 0.2540 & 0.0283 \\ Total dissolved solids (mg/L) & 0.0000 * & 0.5686 \\ Electrical conductivity \(\mu\)S/cm & 0.0000 * & 0.4360 \\ pH & 0.0002 * & 0.0034 \\ Chlorides (mg/L) & 0.0000 * & 0.4176 \\ Fluorides (mg/L) & 0.3992 & 0.0844 \\ Silicon oxides (mg/L) & 0.0315 * & 0.0001 * \\ Potassium (mg/L) & 0.0001 * & 0.2912 \\ Manganese (mg/L) & 0.5720 & 0.8024 \\ Sodium (mg/L) & 0.0000 * & 0.0143 * \\ Sulfates (mg/L) & 0.0000 * & 0.0134 * \\ Calcium (mg/L) & 0.0000 * & 0.2466 \\ Magnesium (mg/L) & 0.0000 * & 0.0058 * \\ Total hardness (mg/L) & 0.0000 * & 0.3337 \\ Water temperature \({}^{\circ}\)C & 0.0000 * & 0.8973 \\ \hline \hline \end{tabular}  
* \(p\)-value \(\leq\) 0.05) is statistically significant.  
\end{table} 
Table 3: Spatial and temporal statistical analysis (ANOVA) of the water quality parameters measured in the Cuemavaca aquifer. Figure 8: Pearson correlation coefficients of the water quality parameters of the Cuemavaca aquifer. Nitrates presented the highest number of correlations with other parameters. This parameter is correlated with TN, TDS, EC, PH, C1-, K+, Na+, SO4, Ca2+, Mg2+, TH, and WT. TA is related to HCO3-, NO3-, TN, TDS, EC, Cl-, Na+, Ca2+, Mg2+, TH, and WT. Bicarbonates showed a high correlation with NO3-, TN, TDS, EC, Cl-, Na+, Ca2+, Mg2+, TH, and WT. Total nitrogen is associated with TDS, EC, Na+, SO4-, Ca2+, Mg2+, and WT. Total dissolved solids are highly related to ions, TH, EC, and WT. The electrical conductivity attributes a higher correlation with Cl-, K+, Na+, SO4-, Ca2+, Mg2+, TH, and WT. Chlorides are significantly related to K+, Na+, SO4-, Ca2+, Mg2+, and TH. Potassium is related to other ions such as Na+, SO4, Ca2+, Mg2+, and TH. In turn, sodium is related to SO4-, Ca2+, Mg2+, and TH. Sulfates are related to Ca2+, Mg2+, and TH, and calcium shows a correlation with Mg and TH. This method has been used for the evaluation of groundwater quality. Strong correlations between major ions are also reported by [PERSON] et al. (2014). This situation evidenced that the groundwater quality of a coastal city in China was affected by various factors, such as dissolution and water evaporation. Since a high amount of groundwater quality parameters were correlated with each other, a hierarchical cluster analysis was carried out (Figure 9). Hierarchical cluster analysis was used to further unearth the main chemical processes controlling groundwater chemistry in the aquifer ([PERSON] et al., 2016; [PERSON] et al., 2017). This analysis included the 23 analyzed parameters and 34 water samples at different times of the year. The dendrogram formed the main cluster which in turn formed two groups. The first group includes only fluorides and sulfates. The second main group is composed of the rest of the water quality analyzed parameters. Several subgroups are evidenced, such as those formed by TDS, EC, and TH, TA, and HCO3-, and SiO2, K, Ca2+, and Mg2+.