## 3 Results
#### Spatial Analyses  
Spatial correlograms were used to estimate the distance at which spatial correlation ceases (equals zero). The maximum distance between a pair of points was 12,009 m, but we observed that the distance at which autocorrelation ceased was much lower in any case (Table 3), ranging from 2 to 4.5 km. These distances were employed for the definition of the spatial weight's matrix for further spatial analyses. Maximum Moran's I values obtained for nitrates and DDT-DDE indicates a higher spatial autocorrelation. Oppositely, total suspended solids had a Moran's I value close to zero, which is related with a random pattern. Then, clusters of high or low correlation were obtained by using the Getis-Ord \((G_{i}^{*})\) statistic (Figure 2). The Vinalopo River mouth seems to agglutinate several clusters of hot-cold spots for different water parameters. The outlet of the river is a drainage channel (_Azarbe de Dalt_) instead of a direct river discharge on the coastline, and this area is very prone to inundation. High-high clusters were observed for EC (Figure 2b) and DDT-DDE (Figure 2e); a clear low-low cluster for pH (Figure 2a) was evident. The floodplains of the Segura River (south and southwest of the study area) were associated with a low-low cluster for EC values (Figure 2b). An extensive hotspot for nitrates was evident in the middle west of the study area (Figure 2d). This portion of the study area is more densely populated than the Vinalopo river mouth (see urban areas indicated in Figure 1). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **pH** & **EC** & **TSS** & **Nitrates** & **DDT–DDE** & **Glyphosate** \\ \hline pH & 1 & - & - & - & - & - \\ EC & \(\mathbf{-0.455\;***}\) & 1 & - & - & - & - \\ TSS & \(\mathbf{-0.077}\) & \(\mathbf{0.248\;^{*}}\) & 1 & - & - & - \\ Nitrates & \(\mathbf{0.053}\) & \(\mathbf{-0.185}\) & \(\mathbf{-0.298\;**}\) & 1 & - & - \\ DDT–DDE & \(\mathbf{-0.194}\) & \(\mathbf{0.392\;**}\) & \(\mathbf{0.011}\) & \(\mathbf{-0.154}\) & 1 & - \\ Glyphosate & \(\mathbf{0.398\;***}\) & \(\mathbf{-0.563\;***}\) & \(\mathbf{-0.121}\) & \(\mathbf{0.227}\) & \(\mathbf{-0.420\;***}\) & 1 \\ \hline \hline \end{tabular}  
Significance levels: (*) = \(p<0.05\); (**) = \(p<0.01\); (***) = \(p<0.001\).  
\end{table} 
Table 2: Spearman rank correlation test results. Significant correlations are highlighted in bold. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Variables** & **Distance for Autocorrelation = 0** & **Moran’s I** & **Kruskal–Wallis for \(G_{i}^{*}\)Groups** \\ \hline pH & 3412 m & 0.100 & 0.005 ** \\ EC & 4546 m & 0.171 & \(\mathbf{<0.001\;***}\) \\ TSS & 2509 m & 0.033 & 0.074 n.s. \\ Nitrates & 4497 m & 0.295 & 0.002 ** \\ DDT–DDE & 3810 m & 0.193 & 0.009 ** \\ Glyphosate & 2133 m & 0.114 & 0.795 n.s. \\ \hline \hline \end{tabular}  
\end{table} 
Table 3: Results from the spatial correlogram, local Moran’s I, and Kruskal–Wallis test. The categorization of the points obtained from the Getis-Ord \((G_{i}^{*})\) statistic (i.e., high-high, low-low, non-significant) was incorporated into the database of the water parameters and used as factors for a Kruskal-Wallis test (Table 3) [33], which could be associated with significant differences between clusters. Besides, box-plots for each parameter were also computed (Figure 3). Significance letters from [PERSON]'s test (\(p<0.05\)) are included in the boxplots. Figure 2: Getis–Ord \((G_{i}^{*})\) statistic results for: (**a**) pH; (**b**) EC; (**c**) TSS; (**d**) nitrates; (**e**) DDT–DDE; and (**f**) glyphosate. Red triangles represent high–high clusters (hotspots), blue circles represent low–low clusters (cold spots), and yellow dots represent non-significant points. The hotspot area of DDT is highlighted with a red ellipse (**e**). Significant differences for the Kruskal-Wallis (\(p\)-value \(<\) 0.05) test were obtained for pH, EC, nitrates, and DDT-DDE. [PERSON]'s test completed and confirmed these results with a post hoc analysis.