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are found for K and NH
3
-N in the whole study area, for NO
2
-N at most of the
sampling sites, and for other water quality indicators at some sites (Fig.
9.6
). The
significant positive correlations indicate that higher PD is associated with higher
concentration of water quality indicators. The significant positive correlations for
SC, Ca, and SO
4
are mainly distributed outside the 20-km buffer, while that for
PO
4
-P are concentrated inside the 20-km buffer, and no clear spatial pattern can be
identified from the maps of
t
-value for other water quality indicators (Fig.
9.6
).
However, the scatter plots of urbanization level and the parameter estimate from
the GWR models show that the relationships between population density and water
quality indicators are significantly associated with the urbanization level in the
watersheds (Fig.
9.7
). The parameter estimates for most water quality indicators
Fig. 9.7
Scatter plots of urbanization levels of watersheds and parameter estimates from the GWR
models for population density and water quality. For each Scatter plot, the
x
axis is percentage of
developed land, and the
y
axis is the parameter estimate from the GWR model for population
density and a water quality indicator
