xiv
List of Figures
Figure 5.5 Minimum stream ANC sampled at each site during each
year versus median spring ANC for all samples collected
at that site during that spring season. Data are provided
for all intensively studied streams within Shenandoah
National Park during the period 1993–1999. A 1:1 line is
provided for reference. The vertical distance from each
sample point upward to the 1:1 line indicates the ANC
difference between the median spring value and the
lowest sample value for each site and year.
143
Figure 5.6 Example box plots to compare hypothetical lake ANC
values measured in samples collected during the spring
versus the fall season. IQR indicates the interquartile
range, or the difference between the 25th and 75th
percentile values.
145
Figure 5.7 Changes in the concentration of major water chemistry
constituents during a hypothetical hydrological episode
in one stream. SBC is the sum of the four base cation
concentrations. Data for each variable of interest are
plotted along the same time axis and compared at the
same scale relative to the pattern of discharge.
150
Figure 5.8 Time series of major ions and discharge in Treasure Lake
in the Sierra Nevada during snowmelt in 1993. Seasonal
and episodic changes in surface water chemistry can be
examined using these simple time series plots.
151
Figure 5.9 Ratio of NO 3
− :(SO 4
2− + NO 3
− ) concentration versus ANC
in stream water samples collected during hydrological
episodes in four streams included in the Adirondack region
of EPA’s Episodic Response Program (ERP). The different
symbols on the graph represent different streams.
152
Figure 5.10 Map of summer NO 3
− concentrations in drainage lakes
sampled by the Adirondack Lakes Survey Corporation in
the Adirondack region of New York. Maps such as this can
reveal spatial patterns in the concentration of any surface
water variable across a study area.
153
Figure 5.11 Map showing the results of a classification system
devised to reveal the locations where low-ANC streams
were expected to occur in the southern Appalachian
Mountains (in this example, based on geology and
elevation) compared with the locations of all streams
List of Figures
Figure 5.5 Minimum stream ANC sampled at each site during each
year versus median spring ANC for all samples collected
at that site during that spring season. Data are provided
for all intensively studied streams within Shenandoah
National Park during the period 1993–1999. A 1:1 line is
provided for reference. The vertical distance from each
sample point upward to the 1:1 line indicates the ANC
difference between the median spring value and the
lowest sample value for each site and year.
143
Figure 5.6 Example box plots to compare hypothetical lake ANC
values measured in samples collected during the spring
versus the fall season. IQR indicates the interquartile
range, or the difference between the 25th and 75th
percentile values.
145
Figure 5.7 Changes in the concentration of major water chemistry
constituents during a hypothetical hydrological episode
in one stream. SBC is the sum of the four base cation
concentrations. Data for each variable of interest are
plotted along the same time axis and compared at the
same scale relative to the pattern of discharge.
150
Figure 5.8 Time series of major ions and discharge in Treasure Lake
in the Sierra Nevada during snowmelt in 1993. Seasonal
and episodic changes in surface water chemistry can be
examined using these simple time series plots.
151
Figure 5.9 Ratio of NO 3
− :(SO 4
2− + NO 3
− ) concentration versus ANC
in stream water samples collected during hydrological
episodes in four streams included in the Adirondack region
of EPA’s Episodic Response Program (ERP). The different
symbols on the graph represent different streams.
152
Figure 5.10 Map of summer NO 3
− concentrations in drainage lakes
sampled by the Adirondack Lakes Survey Corporation in
the Adirondack region of New York. Maps such as this can
reveal spatial patterns in the concentration of any surface
water variable across a study area.
153
Figure 5.11 Map showing the results of a classification system
devised to reveal the locations where low-ANC streams
were expected to occur in the southern Appalachian
Mountains (in this example, based on geology and
elevation) compared with the locations of all streams