Geoscience Reference
In-Depth Information
Table 8.2
Best subsets multiple regression for 26 small catchments and 15 larger catchments. The predictors are the
best simple regression, the best two-variable multiple regression, and the best three-variable multiple regression.
LC
=
land cover (2006), LU
=
land use, devel.
=
developed, comm.
=
commercial, activity
=
real estate activity,
res.
=
residential, LOPI
=
median land ownership persistence index, ag.
=
agriculture, change
=
land cover change
between 2001 and 2006.
Range, small
Best predictors from
Range, larger
Best predictors from
R
2
R
2
Water quality variable
catchments
small catchment data
catchments
larger catchment data
Specific conductance
(summer,
Scm
−1
)
9.3 - 63.5
Forest LC
0.65
15.4 - 52.8
Forest LC
0.65
Forest LC; devel. change
0.78
Activity; land value
0.79
Forest LC; devel.
change; res. LU
0.80
Activity; comm. LU;
devel. LC
0.86
Nitrate-N (summer,
gL
−1
)
20.1 - 390.5
Devel. LC
0.77
42.6 - 390.5
Forest LC
0.80
Devel. LC; comm. LU
0.84
Ag. LC; devel. LC
0.89
Devel. LC; comm. LU;
forest change
0.87
Ag. LC; devel. LC;
forest LC
0.95
Turbidity (winter,
NTU)
1.6 - 17.7
Ag. LC
0.54
0.6 - 8.2
Res. LU
0.37
Ag. LC; ag. LU
0.56
Diversity; comm. LU
0.54
Forest LC; devel. LC;
forest change
0.65
Comm. LU; res. LU;
devel. LC
0.77
Turbidity (summer,
NTU)
0.5 - 15.6
Res. LU
0.14
2.0 - 18.3
LOPI
0.15
Ag. LC; devel. change
0.37
Res. LU; devel. LC
0.38
Forest LC; res. LU; ag. LC
0.47
Comm. LU; res. LU;
devel. LC
0.46
Percentage organic
matter in particles
(summer, %)
19.9 - 69.5
Res. LU
0.53
26.2 - 60.4
Res. LU
0.44
Comm. LU; res. LU
0.56
LOPI; res LU
0.51
Comm. LU; res. LU;
devel. LC
0.58
Land value; res LU;
devel. LC
0.57
Total dissolved
phosphorus
(summer,
gL
−1
)
2.5 - 13.3
Ag. LC
0.06
3.2 - 10.8
Ag. LC
0.22
Res. LU; ag. LC
0.08
LOPI; ag. LC
0.38
Forest LC; ag. LC;
devel. LC
0.22
LOPI; ag. LU; ag. LC
0.60
the small catchments and to parcel data (land use)
in the larger catchments, but summer turbidity was
not very well related to anything measured (Table
8.2, Figure 8.6). Winter and summer turbidity
relationships were very different (Figure 8.6), and
the values were idiosyncratic. In general, turbidity
was high in winter where cattle were upstream of
the sample site and high in the summer if there
were recent construction activities upstream. The
percentage of organic matter in particles was most
strongly related to parcel area (land use) data,
but land value and land ownership persistence
were also significant (Table 8.2, Figure 8.7). Total
dissolved phosphorus was generally very low in all
streams and was not significantly related to any
measured independent variables (Table 8.2).
To quantify mountainside development, the
percentage of developed land-cover pixels that
were also in the upper 60% of the catchment
altitude was determined. Watauga Creek and Jones
Creek catchments illustrate the two extremes
(Figure 8.8). In both catchments, most of the
developed pixels follow the streams and roads.
In the Watauga Creek catchment, there is also a
band of development along the major highway.
About
5%
of
this
catchment
is
mountainside
