Agriculture Reference
In-Depth Information
shed to the fourth order watershed, hardly respond to permanganate index
as a contributing zone.
The defi nition of watershed adaptive response unit based on the basic
watershed units, actually a contributing zone, is very meaningful for the
purpose of more effective watershed management. It is important to ad-
dress the fi ne-scale management issues relate to watershed adaptive re-
sponse units for every water quality parameter. The adjustment of agricul-
tural input structure and intensity may be carried out inside the individual
watershed adaptive response units.
1.4.3 MODELING
The multiple linear regression model performed using log transformed de-
pendent variables, which was adopted in many previous studies to explore
the relationship between land use and stream water, can also provide in-
sight into the linkages between agricultural land use intensity and stream
water quality at multiple watershed scales. The statistical models in this
study are valuable in examining the relative sensitivity of water quality
indexes to alterations in agricultural land use intensity inside the various
contributing zones when coupled with expert knowledge. The modeling
results can also further help to identify the cause-and-effect relationships
between agricultural input intensity and stream water quality inside the
watershed adaptive response units, which are important in the manage-
ment of water quality. The modeling, although statistically significant,
showed the relatively weak coefficients of determination. It may be that
the spatial incompatibility between the watershed spatial unit and the mu-
nicipal/town unit was actually existed, or that other potential factors influ-
encing stream water quality variable were not included in the analysis. All
of these are worthy of further research.
Although multiple linear regression models are an effective approach
for identifying signifi cant agricultural input intensity affecting water qual-
ity and explaining the relationship between agricultural land use intensity
and stream water quality, they do not appear to quantitatively estimate
contribution of respective agricultural land use intensity on the water qual-
ity because they are only based on the existence of statistical signifi cance
