Agriculture Reference
In-Depth Information
In previous studies, the concentration of nutrients over an area can be
described in the form of an exponential model or a linear model consider-
ing the proportions of land use/land cover as explanatory variables. De-
livery of non-point source pollutants from discrete upstream contribut-
ing zones to a particular downstream point is a multi-step, often episodic,
process [25]. A fi rst order rate equation can be used for modeling nutrient
attenuation in fl ow through various land uses to the nearest stream [25].
Since agricultural land use intensity has been one of the most signifi cant
forms of land cover modifi cation, the exponential model was chosen for
this research to explore the relationship between agricultural land use
intensity and water quality, and to recognize how agricultural land use
intensity affects water quality at various watershed scales. Stepwise mul-
tiple regression analysis was performed using log transformed dependent
variables to reduce the asymmetric distribution of the data. The numbers
of scales for 27 monitoring sites were different, thus, the used monitoring
sites and sample number at various scales were different in the multi-scale
regression analyses (Table 7). Because the sample numbers were too small
to make valuable regression analysis above the scale of Zone 5, the multi-
scale regression analyses were carried out with SPSS 13.0 at the scales
from Zone 1 to Zone 5. Based on this statistical analysis, watershed adap-
tive response units for each water quality variable can also be identifi ed.
TABLE 7:
The monitoring sites at various scale level in the multi-scale analyses.
Scale
Sites
Number
Zone 1
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22,
23, 24, 25, 26, 27
27
Zone 2
1, 2, 3, 4, 5, 7, 9, 15, 16, 19, 20, 21, 22, 23, 24, 25, 26
17
Zone 3
1, 2, 4, 5, 7, 9, 15, 16, 19, 20, 21, 23, 24, 26
14
Zone 4
1, 2, 4, 7, 9, 16, 20, 21, 23, 26
10
Zone 5
1, 2, 4, 7, 9, 20, 23, 26
8
Zone 6
1, 2, 4, 7, 20, 23, 26
7
Zone 7
1, 2, 4, 7, 20, 26
6
>Zone 7
<5
