Geoscience Reference
In-Depth Information
scientists and environmental protection agency to trace specific pollution sources.
Thus, GWR provides a useful tool for policy makers, regional and local agencies,
and researchers to unveil the local pollution causes, and to adopt appropriate urban-
ization indicators based on the dominant pollutant appearing at the local sampling
sites to better assess the pollution status and improve watershed conservation and
management.
9.7 Conclusions
This chapter interprets the results from the application of GWR to analyze the rela-
tionships between two urbanization and fourteen water quality indicators in eastern
Massachusetts. Most of water quality indicators, including SC, dissolved ions and
solid, and dissolved nitrogen parameters have significant relationships with per-
centages of developed land and population density. This result indicates that water
pollution is associated with urbanization. Nevertheless, the impact of urbanization
on water quality changes over space in response to the urbanization levels of water-
sheds. The relationships of the two urbanization indicators and most of water quality
indicators increase as the urbanization levels of watersheds decrease. Thus, the
adverse impact of urbanization on water quality is more substantial in less-urbanized
areas than it in highly-urbanized areas. The same degree increase in population den-
sity and developed land have more adverse impact on water quality in less-urbanized
suburban areas than highly-urbanized central cities.
This result might be caused by the dominant development pattern in US. Urban
sprawl, the land-consumptive pattern of suburban development over decades in the
US, encourages low-density land development in less-urbanized suburban areas.
Under this development pattern, per capita land use, energy consumption, and pol-
lution generation are all higher in suburban areas than central cities, and so the
adverse impact of urbanization on natural environment is assumed to be more sig-
nificant in suburban areas. The more significant adverse impact of urbanization on
water quality in suburban areas than central cities found by this study provides
an important evidence to prove the above assumption. To control or reduce the
impact of urbanization on water quality, an alternative urbanization pattern, smart
growth, which promotes compact, transit-oriented, walkable, and bicycle-friendly
land development in central cities, should be encouraged. The redevelopment in
central cities, which is already highly-urbanized, has lower adverse impact on water
quality than new development in less-urbanized suburbs as indicated by the results
of this study. Thus, this study provides an additional evidence for policy mak-
ers to oppose urban sprawl and to support smart growth, and can have important
implications on environmental policy and management.
This study also proves that GWR can be a very useful geospatial technology for
environmental research, policy, and management. GWR is able to detect the spa-
tially varying relationships between urbanization and water quality indicators, the
changing abilities of urbanization indicators to explain water quality change over
