## 3 Results  
Descriptive statistics (Table 1) provided information about the main characteristics of the water parameters measured. A summary of the main characteristics for each water course is also include in the Supplementary Materials (Table S1). The number of samples employed in the analyses was 76, except for DDT-DDE (\(n=69\)), due to the existence of some samples with very low concentrations.  
Mean pH was 7.9 and exhibited low variability as denoted by a relatively low standard deviation of only 0.2. Electrical conductivity ranged from 2.3 to 18.2 mS/cm. These medium-high EC values are characteristic of the area, where the geological factors, along with a semiarid climate and intensive agriculture practices, promote high salinity in surface water and groundwater [37]. Mean TSS was 68.8 mg/L and the standard deviation was quite high (73.7 mg/L). We found a high variability of TSS values, from very low (minimum = 2.4 mg/L) to quite high values (maximum = 538.8 mg/L). The mean nitrate concentration was 22.1 mg/L with a maximum of 49.9 mg/L (RSD = 60.3%). The last two water quality parameters were DDT-DDE and glyphosate. Seven of the 76 water samples exhibited DDT-DDE concentrations lower than the lower detection limit (0.625 ug/L), and were discarded for further analysis. Mean values were 1.45 ug/L for DDT-DDE and 2.04 ug/L for glyphosate. DDT-DDE and glyphosate had similar relative standard deviation values (60.2% and 64.6%, respectively). The highest concentration for DDT-DDE was 6.5 ug/L, while the highest concentration for glyphosate was 6.2 ug/L. Based on the Shapiro-Wilk test, we evidence that all variables--except pH--does not adjust to a normal distribution (\(p\)-value \(<0.05\)). This result was considered for further statistical analyses; thus, limiting the employment of a parametric test.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Variables** & **Min.** & **Max.** & **Mean** & **SD** & **RSD (\%)** & **Shapiro–Wilk** \\ \hline pH & 7.4 & 8.4 & 7.9 & 0.2 & 2.4 & 0.345 \\ EC (mS/cm) & 2.30 & 18.16 & 5.63 & 3.07 & 54.6 & \textless{}0.001 \\ TSS (mg/L) & 2.40 & 538.80 & 68.76 & 73.70 & 107.2 & \textless{}0.001 \\ Nitrates (mg/L) & 0.54 & 49.87 & 22.13 & 13.34 & 60.3 & 0.024 \\ DDT-DDE (ug/L) & 0.70 & 6.53 & 1.45 & 0.87 & 60.2 & \textless{}0.001 \\ Glyphosate (ug/L) & 0.12 & 6.24 & 2.04 & 1.32 & 64.6 & 0.004 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Descriptive statistics of the water characteristics of the drainage channels: minimum and maximum values, arithmetic mean, standard deviation (SD), and relative standard deviation (RSD). Shapiro–Wilk test of normality was included.  
Bivariate correlations among water quality parameters were assessed with the non-parametric Spearman rank correlation test (Table 2). We focused our attention on the significant correlations among pesticides and the other water parameters. A significant and negative correlation between glyphosate and DDT-DDE was found. Moreover, both pesticides were significantly correlated with EC, but in different ways. In this sense, EC was positively correlated with DDT-DDE, and negatively correlated with glyphosate. Additionally, EC was negatively correlated with pH and positively correlated with TSS. Finally, we found that nitrates were only negatively correlated with TSS.  
After the computation of descriptive statistics and correlations among variables, several spatial analyses were developed in order to consider the water parameters and the relation with their environments.