Geoscience Reference
In-Depth Information
ions have significant negative correlations with PDLU. In other words, the relation-
ships between developed land and these water quality indicators decrease as the
urbanization level of watershed increases. On the contrary, the parameter estimates
for most of dissolved nutrient parameters have significant positive correlations with
PDLU, indicating that the relationships between developed land and dissolved nutri-
ent parameters increase as the urbanization level of watershed increases. Therefore,
a clear spatial pattern exists in the study area: the correlations of developed lands
with SC, DS, and dissolved ions are stronger in less-urbanized areas, while the
correlations with dissolved nutrients are stronger in highly-urbanized areas.
This spatial pattern is also observed in the maps of local
R
2
value (Fig.
9.5
).
The local
R
2
values show great spatial non-stationarity. SC, DS, and most dis-
solved ions, such as Na, Cl, and Mg, have higher local
R
2
values at many sampling
sites outside the 20-km buffer, but lower local
R
2
values inside the 20-km buffer
(Fig.
9.5
). In contrast, the local
R
2
values for dissolved nutrient indicators, including
NH
3
-N, NO
2
-N, and NO
3
-N + NO
2
-N, are lower at many sites outside the 20-km
buffer, but higher inside the 20-km buffer (Fig.
9.5
). However, the higher local
R
2
Fig. 9.5
Local
R
2
values for the GWR models of developed land and water quality
