Spatial variations in water quality between the studied rivers in wet season. Spatial variations in water quality between the studied rivers in wet and dry seasons were studied to evaluate the spatial patterns in the water quality of rivers. Three major rivers of South Florida were the grouping (dependent) variable, while the observed parameters in each season constituted the independent variables. Both standard and stepwise modes of DA were applied. First, the spatial variations in water quality between the studied rivers in the wet season were evaluated. As shown in Table 5, the values of Wilks' lambda and the chi-square for each DF varied from 0.217 to 0.804 and from 35.635 to 133.646. P-values were all less than 0.01, indicating that the spatial DA was credible and effective. In the stepwise DA, only five variables (TKN, TP, ammonia-N, magnesium, and sodium) were selected as the most important discriminating variables. The two DFs explained 78.7 and 44.3% of the group differences, respectively. The first DF separated Miami Canal from Kissimmee River and Caloosahatchee River (Figure 3), and was significantly and negatively correlated with total phosphate and TP (Table 6). The second DF established some separation between Kissimmee River and Caloosahatchee River, and was significantly correlated with chl-a. The CFs and CMs obtained from the two modes are shown in Tables 7 and 8. In the standard mode, all 12 variables were included and the constructed CFs produced 80.2% accuracy in assigning cases. However, in the stepwise mode, DA produced 79.2% correct assignment using only five discriminating variables.