20080868 Ver 2_Section III C Water Quality 2021 PCS Creeks Report_20220605

C. WATER QUALITY
(Section III. C. was prepared by Dr. Suelen Tullio, the laboratory manager in the
Environmental Research Laboratory of East Carolina University with assistance from Dr.
Siddhartha Mitra, Professor of Geological Sciences, East Carolina University, Greenville, NC).
1.0 History
Water quality monitoring sites on three creek systems were initially established in
1998 as follows: (1) two locations in Jacks Creek, (2) three locations on Tooley Creek, and (3)
four locations on Huddles Cut (Figures I-B3, I-B10, and I-B13). These stations were monitored in
accordance with the 1998 plan and continued under the final 2011 plan as outlined in Table I -Al .
By December 2011, two stations each in six additional creeks (three control creeks and three
creeks to be impacted) had been added such that ten creeks designated for water quality
monitoring were part of the regular program (no water quality samples have ever been collected
in Muddy Creek).
Water quality stations at two locations were added in the following creeks in 2011:
Little Creek- LCWQ1 and LCWQ2, one at each of the salinity stations (Figure I-B5). Jacobs Creek-
JCBWQ1 near the upstream salinity station and JCBWQ2 near the old railroad trestle (Figure I-
B6); Project Area 2 (PA2) - PA2WQ1 at the upstream end of the main channel and PA2WQ2 at
the midstream salinity station (Figure I-B7); Drinkwater Creek- DWWQ1 at the upstream well array
and DWWQ2 near the upstream salinity station (Figure I-B8); Long Creek- LOCWQ1 and
LOCWQ2, one at each of the salinity stations (Figure I-B9); Porter Creek- one downstream of the
most upstream well array (PCWQ1) and PCWQ2 at the upstream salinity station (Figure I-B14);
and Duck Creek- DKCWQ1 at the upstream salinity monitor and DKCWQ2 at the downstream
salinity monitor (Figure I-B18). With the addition of two stations in 2013 on two small, unnamed
tributaries (UTs) to Durham Creek, DCUT11 (DC11WQ1; Figure I-B16 and DCUT19 (DC19WQ1;
Figure I-B17) all water quality stations designated in the study plan north of NC Highway 33 were
in place.
In 2018, two additional creeks were added to the study: Broomfield Swamp Creek,
a future impact creek (Figure I-B1), and SCUT1, an unnamed tributary to South Creek as a control
(Figure I-B2); however, the 2018 data record was incomplete for the year for all parameters and
no data analysis was performed. The data record for both Broomfield Swamp Creek and SCUT1
started being included in the analysis for the water quality report in 2019.
a. Description of Analysis Techniques
Multivariate analysis was used to analyze all water quality data. Since the
2015 report on data collected through 2014 (CZR 2015), the data have been divided into two data
sets. The first data set (Data Set 1) consists of data from 1999-2011 in Huddles Cut, Jacks Creek,
and Tooley Creek with no new data added; therefore, this data set has not been repeated in any
recent annual report. The second data set (Data Set 2) consists of all stations with data from
2012-to present. The reason that these two data sets were separated was to avoid bias from
longer data sets on the principal components structure. For temporal and spatial analysis of these
creeks for the earlier years, please refer to the 2015 report (CZR, 2015). In each subsequent
annual report, Data Set 2 has been updated with data from the current year and analyzed for
temporal and spatial variability; however, in analysis for this section of the report, the entire data
set (1999-current data collection year) was used to compare conditions in pre -Mod Alt L and post -
Mod Alt L years. Pre- and post -Mod Alt L data were compared at Jacks Creek, Jacobs Creek,
Drinkwater Creek, Tooley Creek, Huddles Cut, Porter Creek, and DCUT11. The pre- and post -
Mod Alt L divisions are shown in Table III-C1.
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Temporal variability at water quality stations across years was analyzed via
a Principal Components Analysis (PCA) to recombine all water quality variables into the loading
components that capture the intercorrelation between variables; in this context "loading" is
synonymous to "contributing". PCA has two primary uses: 1) to describe interrelationships
between a matrix of intercorrelated variables and 2) data reduction, (i.e., to reduce a large matrix
of intercorrelated variables into linear recombinations, or principal components (PC) of the original
variables). A missing value results in no PC values, thus, to decrease the number of gaps in the
data (missing values) when a variable was reported with a value below detection, the detection
value was used. Actual gaps in the PC interannual variability graph usually indicate there was
not enough water to collect a sample. The PCA plots all original variables in multidimensional
space (one dimension for each variable), and then fits a regression line through these multiple
dimensions. The principle of least squares is used to fit the regression line and the resulting
variance explained is recombined into a principal component that explains a fraction of the total
variation. This procedure is repeated, (i.e., a new regression line is fitted to the remaining data),
and a new principal component is calculated and generated, until all variability is explained. The
PCs themselves are uncorrelated to each other and therefore may be used in further modeling
without violation of regression assumptions. The PCs can be related to the original variables by
examination of the loadings on to each PC, and these values represent the degree of correlation
of each original variable to the new PC. To examine how the PCs are related to one another, a
loading plot is generated to show how the original variables are related to the first two PCs. The
resulting set of PC values represents new variables, made from the original variables, but fewer
in number and uncorrelated to each other. Plotting the PC scores over the course of the years
shows the temporal variability of multiple variables, without the need to generate numerous plots.
A PCA analysis was run for each water quality station and the biplot, loadings, and PC time series
are presented. Although it is customary to examine all PCs until approximately 80 percent of the
variance is explained, to reduce the number of graphs in the report, only the first two PCs were
graphically represented (the ones that explain the majority of the variance).
Spatial variability among stations across all years was analyzed by
comparison of the yearly means of each water quality parameter at each monitoring station using
a cluster analysis, a multivariate technique that analyzes similarity or dissimilarity computed from
a data matrix. For example, a single water quality monitoring station may be characterized by
multiple water quality measurements. Thus, one might ask: how similar are two water quality
stations from two different creeks based on all of the water quality measurements? While it is
straightforward to compare salinity values between the two creeks, the addition of more
parameters makes the comparison more complex. This comparison of the data matrix of water
quality values was done by grouping by station while a dissimilarity matrix was calculated, and a
plot of the water quality values for each parameter in multivariate space was built. Instead of fitting
a regression line, as with PCA, the Euclidean distance is calculated between the water quality
values for each station. Values that are close to each other in space have low dissimilarity and
values that are far apart in space have high dissimilarity. Once the dissimilarity matrix was
computed, the dissimilarity values for each station were clustered and displayed using a
dendrogram (tree diagram). This analysis examines relationships between stations and groups
water quality monitoring stations with similar conditions. Doing this over multiple years aims to
demonstrate how relationships between stations might change over time. The location of each
station relative to the Pamlico River (upstream vs. downstream) was also included in the spatial
analysis to determine if distance from the river was a factor underlying relationships between
water quality monitoring stations. (As the data collection location figures in Section I.B show,
upstream water quality station locations are various distances from downstream stations from
creek to creek and some upstream stations in some creeks are actually closer to the river than
some downstream stations in other creeks; however, upstream stations are shallower than
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downstream stations). Water quality conditions for each group of stations were then summarized
graphically. Individual water quality values for all parameters by group are also shown as means
and standard deviation bar graphs to indicate the variability of each parameter within each
individual group or cluster.
Finally, to compare interannual variability in water quality parameters
pre- and post -Mod Alt L, the full time series of data from Jacks Creek, Jacobs Creek, Drinkwater
Creek, Tooley Creek, Huddles Cut, Porter Creek, and DCUT11 were used as shown in Table III-
C1. Pre- and post -mod Alt L conditions were compared using a one-way ANOVA, and t scores
and p-values were presented. Differences were considered significant if p-values were <_ 0.05. It
is important to note that the number of samples analyzed (N) has an effect on the ability to detect
differences pre- and post -impact. The greater the number of samples used to detect changes in
mean water quality parameter values pre- and post -impact, the greater the chance that a change
will be detected. It is also important to differentiate between statistical significance versus
practical (or in this case, ecological) significance (Amrhein et al., 2019; Dushoff et al., 2019;
Martinez-Abrain, 2008; Van Calster et al., 2018). The discussion around null hypothesis
significance testing (NHST) and ecological significance involves the ideas that NHST does not
provide important information, that is, the magnitude of an effect and the precision of the estimate
of the magnitude of that effect. NHST approaches inform the probability of the observed data to
test if the null hypothesis is true, conversely it lacks information about the potential changes in
ecosystem function and structure (Halsey, 2019; Nakagawa and Cuthill, 2007; Wasserstein et al.,
2019; White et al., 2013). The debate about use of other metrics to assess potential changes
continues, but for continuity with previous reports this familiar metric will be used. Additionally,
whether any changes in magnitude for the water quality parameters might indicate ecological
changes will continue to be assessed.
2.0 Results
Seventeen water quality parameters were analyzed for most creeks (Table III-C2).
Two of those parameters are considered biological (chlorophyll a and dissolved oxygen) while the
remainder are considered biochemical and are either conservative (e.g., salt and pH) or non -
conservative (e.g., nutrients). Locations of water quality sample stations are shown in Figures I-
B1-I-B3, Figures I-B5 - I-B10 and Figures I-B13 - I-B14, and Figures I-B16 — I-B18.
a. Temporal variability (2012-2021) in all creeks
Principal Components Analysis revealed significant interrelationships
between all water quality variables (Table III-C2) and showed the seasonal (Figure III-C1) and
interannual variability (Figure III-C2 through Figure III-C32). The biplot of the visual relationship
between the variables is shown in Figure III-C1. Variables with arrows pointing in the same
direction are positively correlated with each other, variables with arrows pointing the opposite
direction are negatively correlated with each other, and variables at right angles with each other
are not correlated. Each quadrant shows the prevailing conditions when PC1 and PC2 are
positive or negative and can be interpreted as seasonal changes in a clockwise manner. Upper
right quadrant corresponds to spring, lower right to summer, etc. During spring, turbidity,
ammonium, nitrate, total nitrogen, and dissolved organic carbon are highest indicating freshwater
inputs (Figure III-C1). As spring transitions to summer, total dissolved phosphorus, and
orthophosphate peak showing more estuarine inputs (Figure III-C1). Summer conditions consist
of peaks in temperature, particulate phosphorus, particulate nitrogen, chlorophyll a, and dissolved
Kjeldahl nitrogen (Figure III-C1). Fall conditions are characterized by peak salinity, conductivity,
and pH values for the year and depth values increase during the transition to winter (Figure III-
C1). Winter conditions have the highest values of dissolved oxygen (Figure III-C1). This seasonal
distribution of parameters has been observed since 2015 with the one exception of nitrate in 2016
which peaked in summer. The individual time series for each station in all creeks are discussed
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in the following subsections.
i. Broomfield Swamp Creek water quality station BSCWQ1
This station is an upstream station with a clear seasonal pattern in
which PC2 values were higher in the first five months (Figure III-C2). However, the values for
PC1 were higher than PC2 during the summer.
ii. Broomfield Swamp Creek water quality station BSCWQ2
The seasonal trend for this station was almost identical to BSCWQ1
with higher values for PC2 in the first five months, while PC1 shows higher values in the summer
(Figure III-C3). The main difference was the clearer separation in values in the last three months
for PC2. The response of PC1 at this midstream station seems to indicate more estuarine
influence (low values on the PC1 axis represent higher conductivity and salinity (Figure III-C1)).
Broomfield Swamp Creek water quality station BSCWQ3
The seasonal pattern detected for the previous two stations
continued with higher values for PC2 early and late in the year and PC1 value fluctuation around
0 during fall and winter (Figure III-C4). The attenuation of values for PC1 compared to the
previous two stations suggests even more estuarine influence (station is located almost at its
confluence with South Creek).
iv. SCUT1 water quality station SC 1 WQ 1
The PC values for this upstream station clearly indicate higher
values for PC2 in the early and later part of the year with higher PC1 values during the spring,
summer, and early fall (Figure III-05). This seasonality in PC values was similar to the one
identified in Broomfield Swamp Creek.
v. SCUT1 water quality station SC 1 WQ2
The seasonal pattern for this station was, again, higher values for
PC2 during late fall and winter and high values for PC1 during spring, summer, and early fall
(Figure III-C6). The initial response of PC1 in early summer was stronger than on the upstream
station.
vi. SCUT1 water quality station SC 1 WQ3
Although the seasonal signal persisted in this downstream station,
the response was more muted for PC1 than in the previous stations (Figure III-C7). Overall, the
values for the summer vary from 0 to 2.8. The PC2 values followed the pattern indicated in the
other two SCUT1 stations in which winter values were higher.
vii. Jacks Creek water quality station JWQ 1
The seasonal trend for PC1 was mostly positive (freshwater
influence) over the time series, with most peak values in the summer (Figure III-C8). PC2
presents a similar annual cycle with lower magnitude values overall and more negative values
across the year with most of the peak values in the summer (Figure III-C8). Both PC1 and PC2
fluctuated in magnitude over time, an indicator of water quality variability at this station over the
seasonal cycle.
vii. Jacks Creek water quality station JWQ2
The general seasonal trend for PC1 was negative during the winter
months (estuarine influence) and positive in the warmer months (Figure III-C9). PC2 showed an
opposite annual cycle with peak values earlier in winter (Figure III-C9). Both PC1 and PC2
presented a typical seasonal cycle for the 2021 year. Comparatively speaking, the variability of
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both PCs for this year seems lessened when compared to previous years.
viii. Little Creek water quality station LC WQ 1
The seasonal trend showed positive peaks in magnitude in the
summer and negative values for PC1 during the winter when compared to PC2 values (Figure III-
C10). PC2 followed the opposite pattern and tended to peak earlier in the year with lower values
in the summer; however, it remained largely positive from terrestrial runoff influence (Figure III-
C10) as indicated by the parameters prevalent on the positive side of the PC2 axis in Figure III-
C1.
ix. Little Creek water quality station LCWQ2
The general seasonal trend for PC1 was negative throughout 2021
with peaks in positive magnitude in the summer, while some PC2 values were positive with peaks
through the winter months (Figure III-C11) and minimal values during summer. Both PC1 and
PC2 showed less fluctuations over time compared to LCWQ1; a typical indication of
environmental stability at this downstream creek station. The 2021 variability was typical for this
station and similar to previous years (with the exception of 2017).
x. Jacobs Creek water quality station JCB WQ 1
The 2021 seasonal trend for PC1 was positive in summer as in
previous years (max value of 2.77 on June 30, 2021; Figure III-C12). PC2 annual cycle was
similar to previous years with peak values typical in the winter (Figure III-C12). Although the
magnitude of variability in PC2 was higher in the pre -Mod Alt L years, PC2 water quality at this
station has become more stable within a typical seasonal cycle as evidenced by the smaller
variation in magnitude since 2014 and since 2018 for PC1.
xi. Jacobs Creek water quality station JCBWQ2
The 2021 seasonal trend for PC1 was similar to the previous year,
with near zero values in late summer, while PC2 varied around zero with higher values in late fall
to winter (Figure III-C13). Both PC1 and PC2 showed little fluctuation in magnitude over time;
water quality at this station was stable with a typical seasonal cycle with increased estuarine
influence in winter.
xii. PA2 water quality station PA2WQ 1
The seasonal trend for PC1 continued to be positive in summer and
negative in winter, while PC2 was opposite (Figure III-C14). The fluctuation in both PC1 and PC2
over time followed the typical seasonal pattern. Values for PC1 and PC2 in 2021 were in line with
the historical record (with exception of 2019 which showed more variability for both PC1 and PC2
late in winter).
xiii. PA2 water quality station PA2WQ2
This station shows a very clear general seasonal trend for both
PCs. PC1 was negative throughout the year with peak values in the late summer, early fall while
PC2 fluctuates between 0 and 2.4 (Figure III-C15). Both PC1 and PC2 vary over time in minimal
fashion with little overlap in values.
xiv. Drinkwater Creek water quality station DWWQ 1
The seasonal trend for PC1 is positive for most of 2021 with
maximum values during the summer (max value of 4.81 on June 16, 2021; Figure III-C16). PC2
values become negative as the year progressed (Figure III-C16). Both PC1 and PC2 values are
within the observed historical record.
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xv. Drinkwater Creek water quality station DWWQ2
The seasonal trend showed PC1 became positive as summer
began (max value 2.40 on June 30, 2021) and then became negative from September through
the end of the 2021 (Figure III-C17). Although PC2 showed an opposite annual cycle or behavior
pattern to PC1, both PCs presented the most negative values during winter in 2021 (PC1: -3.48
and PC2: -0.95; Figure III-C17). Both PC1 and PC2 show a muted fluctuation in magnitude over
time than the upstream station with a relatively stable seasonal cycle.
xvi. Long Creek water quality station LOCWQ 1
The seasonal trend for PC1 in 2021 and across the time series was
negative throughout most of the year, with peaks in magnitude in the summer and fall (Figure III-
C18). PC2 fluctuated from 0 to 2 over the time series (Figure III-C18). Overall, PC1 showed
increased fluctuation in magnitude in 2012, 2017, and 2018, an indicator of estuarine influence at
this station.
xvii. Long Creek water quality station LOCWQ2
The trend for PC1 was negative throughout the year, with the low
values during winter 2021 (Figure III-C19). PC2 fluctuated with mostly negative values but well
within the historical variation (Figure III-C19). With the exception of 2014-2016, summer values
for this station overlapped, and summer values over the entire time series showed little fluctuation
in magnitude; indicators that summer water quality seems most stable.
xvix. Tooley Creek water quality station TWQ 1
The general seasonal trend for PC1 was positive throughout the
year with peaks values in the summer (Figure III-C20). The only exception was late fall which
PC1 showed negative values. The 2021 PC2 values became negative during summer, which
remained negative for the rest of the year (Figure III-C20). Both PC1 and PC2 showed increased
fluctuation over time.
xx. Tooley Creek water quality station TWQ2
Both PC1 and PC2 had considerable variability throughout 2021
(Figure III-C21). This site continues to periodically experience insufficient water levels for sample
collection throughout the year, thus the gaps in the data set. Due to the variability in water level,
it is not surprising that water quality values fluctuate (Figure III-C21). Despite the gaps, the general
trend for PC1 was positive while PC2 values were negative.
xxi. Tooley Creek water quality station TWQ3
The overall seasonal trend for PC1 was negative throughout 2021
and showed peak values in the summer (Figure III-C22). PC2 values showed minimal variability
over the time series although 2016 through early 2018 showed more positive values compared to
other years (Figure III-C22). Summer and fall of 2021 showed a convergence of values for PC1
and PC2, a sign of stability (i.e., minimal water inputs/exchange).
xxii. Huddles Cut water quality station HWQ 1
The 2021 seasonal trend for PC1 was positive throughout the year
but showed some fluctuations with high values as observed in the previous years (Figure III-C23).
PC2 mirrored the PC1 annual cycle, as customary, with mostly negative values throughout 2021
(Figure III-C23) while low positive values occurred in winter 2018, 2019, 2020, and 2021.
xxiii. Huddles Cut water quality station HWQ2
The general seasonal trend for PC1 was largely positive with peaks
in the summer (max value of 8.05 on July 14, 2021) and lower values in the winter (Figure III-
C24). PC2 peaked in the winter, with most negative values in the summer and fall (Figure III-
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C24). Both PC1 and PC2 showed large fluctuations throughout 2021.
xxiv. Huddles Cut water quality station HWQ3
The historical seasonal trend for PC1 remained positive throughout
the 2021 data record and increased over time (Figure III-C25). PC2 showed a similar annual
cycle but fluctuated closer to zero throughout the year with few positive values; no change in the
historical trend was apparent (Figure III-C25). Both PC1 and PC2 fluctuated throughout the year
with values which followed the established pattern but were lower in magnitude, with some
exceptions (May 2017, July 2018, July 2020, May 2021, and July 2021).
xxv. Huddles Cut water quality station HWQ4
The 2021 seasonal trend for PC1 was similar to the historical record
(Figure III-C26). This station seems to have a rapid response to water level changes. The
variability of PC1 appeared to increase since 2016, and the magnitude of fluctuations observed
in 2021 were in line with the historical record. The years 2015 and 2016 remain the only years
when PC1 was positive all year, an indicator of more terrestrial runoff at this station. The PC2
values were generally negative over the time series with a similar annual cycle to PC1; however,
it became more negative in late summer and fall (Figure III-C26).
xxvi. Porter Creek water quality station PC WQ 1
The general seasonal trend for PC1 seemed to be positive in
summer and less positive or negative in winter (Figure III-C27). PC2 had a similar temporal
pattern of less apparent magnitude than previous years (Figure III-C27).
xxvii. Porter Creek water quality station PCWQ2
The 2021 seasonal trend showed the historical established trend of
PC1 positive values during the summer and less positive or negative during winter (Figure III-
C28). PC2 peaked in early spring and reached maxima negative values in late summer/early fall
(Figure III-C28).
xxviii. DCUT 11 water quality station DC 11 WQ 1
The general seasonal trend for PC1 was negative most of the year
with high negative values in late fall and winter (Figure III-C29). PC2 overlaps the PC1 pattern in
the summers (Figure III-C29). Both PC1 and PC2 showed fluctuations in magnitude over time
opposite in trend with each other.
xxix. DCUT19 water quality station DC19WQ1
The historical seasonal trend for PC1 was positive in summer and
negative in winter (Figure III-C30). For 2021, PC2 values were positive with peaks through the
winter months and were of lesser variability than previous years (Figure III-C30). The overall
pattern for both PCs was similar to station DC11 WQ1 although the range of variability had less
range in values.
xxx. Duck Creek water quality station DKCWQ 1
The general seasonal trend for PC1 was positive in summer and
negative in winter. PC2 showed a similar annual cycle; however, most peaks occurred in spring
and winter (Figure III-C31). Both PC1 and PC2 continued to show a reduction of fluctuations in
magnitude over time and overlaps occurred in summer. Water quality at this station seems more
stable and with a typical seasonal cycle.
xxxi. Duck Creek water quality station DKCWQ2
The general seasonal trend for PC1 was largely negative
throughout the year, with less negative or slightly positive values in summer (Figure III-C32). PC2
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shows a similar annual cycle but fluctuated also near to zero but positive throughout much of the
years with peaks in spring and late winter (Figure III-C32). Both PC1 and PC2 showed typical
seasonal cycles; minimal fluctuation in magnitude over time and summer overlaps to indicate that
water quality was relatively stable.
b. Spatial variability (2012-2021) in all creeks
As in the previous reports, the cluster analysis revealed five distinct groups
of water quality station/years based on similarity or dissimilarity computed from the data matrix of
all water quality variables (Figure III-C33). A summary of all water quality conditions across the
five groups is shown in Table III-C3.
Group A was the second largest group of the station/years of all groups
(79) and consisted primarily of 34 upstream station/years from Duck Creek, Little Creek, Porter
Creek, Broomfield Swamp Creek, and SCUT1 and 45 downstream station/years from Drinkwater
Creek, DCUT11, DCUT19, Porter Creek, Duck Creek, Broomfield Swamp Creek, and SCUT1
(Figure III-C33). This group had a mix of intermediate values for most water quality parameters
compared to other groups, although it also had the lowest average for pH and particulate nitrogen
and the highest depth and nitrate values (Table III-C3). Group B was comprised of 50 upstream
station/years in Drinkwater Creek, Huddles Cut, Jacks Creek, Tooley Creek, and Porter Creek
and 19 downstream station/years in Huddles Cut and DCUT19 (Figure III-C33). This group had
intermediate values for all water quality parameters (Table III-C3). Group C was the smallest
cluster with one upstream station/years in Huddles Cut. This group had the highest average
conductivity and the lowest average for depth, temperature, dissolved oxygen, and nitrate values
(Table III-C3). Group D consisted of 11 upstream station/years from Huddles Cut and Tooley
Creek and two downstream station/years in Huddles Cut. This group had the lowest average
salinity and conductivity, but the highest turbidity, ammonium, DKN, particulate nitrogen, total
dissolved nitrogen, orthophosphate, total dissolved phosphate, particulate phosphate, chlorophyll
a, and dissolved organic carbon. Group E had most of the stations/years of all groups (103) and
consisted primarily of 30 upstream station/years from Jacobs Creek, Long Creek, and PA2 which
represented about 22 percent of the group, and 73 downstream station/years from Duck Creek,
Jacobs Creek, Jacks Creek, Little Creek, Long Creek, PA2, Tooley Creek, Porter Creek, and
DCUT19 comprised the remainder of this group (Figure III-C33). This group had the highest
average salinity, temperature, dissolved oxygen, and pH, whereas it had the lowest turbidity,
ammonium, DKN, total dissolved nitrogen, orthophosphate, total dissolved phosphate, particulate
phosphate, chlorophyll a, and dissolved organic carbon concentrations (Table III-C3).
i. Depth
Depth (in) varied across the five groups. Groups A and E mean
depths were the highest while groups D, B and C had lower depths (Figure III-C34). Note that
groups A and E had a mixture of upstream and downstream stations, resulting in large standard
deviation values, indicating the different responses at these locations to variations in wind tide,
runoff, and/or catchment size. In contrast, group C and D members were mostly upstream but
consistent in depth.
ii. Temperature
Mean temperature (°C) showed small scale variability across three
of the five groups (Figure III-C35). Groups B and E showed the largest range in standard
deviation.
Salinity
Salinity showed substantial variability across the group means
(Figure III-C36) which were significantly different. Group E, comprised of predominantly
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downstream station/years more subject to variations in river discharge, had the highest mean
salinity; group A, B, and E had similar variability to each other.
Conductivity
Mean conductivity (mS) for group C was the highest while the rest
of the groups had similar values to each other (Figure III-C37), albeit this group is only one station.
Groups A, B, and E showed similar variability in salinity.
iv. Turbidity
Turbidity (NTU) showed large standard deviations and some
variability across the means across the groups (Figure III-C38) with the broadest standard
deviation computed at group D. Group E had the lowest mean in spite of being the first group
with the most station/years.
v. Dissolved oxygen
Dissolved oxygen (mg L-1) showed some variability across group
means (Figure III-C39). Group C had the lowest mean dissolved oxygen value (Figure III-C39)
but overall, no biological conclusion can be drawn.
vi. pH
pH was similar across four group means (Figure III-C40) with group
E having the highest average pH (7.16, almost neutral) and highest salinity (7.99) (Table III-C3).
vii. NH4 (ammonium)
NH4 (mg L-1) showed large variability in means among the five
groups (Figure III-C41) with concomitant wide ranges in standard deviation. Differences among
groups were significant. Group E had the lowest mean, and the larger standard deviation was
computed for group D.
viii. NO3 (nitrate)
NO3 (mg L-1) concentration means were low among the B, C, D, and
E groups. Group A had the highest mean and standard deviation, and it was significantly different
from the other groups (Figure III-C42).
ix. DKN (dissolved Kjeldahl nitrogen)
DKN (mg L-1) varied in mean concentration values across all
groups. Group D had higher mean and standard deviation values (Figure III-C43).
xi. PN (particulate nitrogen)
PN (mg L-1) mean concentrations (Figure III-C44) had a similar pattern among the group means
as DKN (Figure III-C43). Group D had highest mean concentration and standard deviation values.
The next highest mean value was group C.
xii. Total dissolved nitrogen
Total dissolved nitrogen (TDN mg L-1) showed some similarities
across all group means although D had a higher mean (Figure III-C45) with a distribution pattern
of concentration means similar to both PN and DKN concentrations. Groups A and D had large
standard deviations when compared with the other groups.
xiii. PO4 (orthophosphate)
PO4 (mg L-1) also showed a similar pattern to PN and DKN mean
concentration values (Figure III-C43, Figure III-C44). Group D presented the highest mean
concentrations of orthophosphate and widest range (Figure III-C46). Overall, the values are
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comparable to historic records in both the Pamlico (Hobbie, 1970; Taft and Taylor, 1975) and the
Neuse Rivers (Christian et al., 1991).
xiv. TDP (total dissolved phosphate)
TDP (mg L-1) mean concentration values (Figure III-C47) showed
the same trend among groups as was seen for PO4 (Figure III-C46) albeit with higher means, as
expected given that this parameter includes both dissolved organic and inorganic phosphate
species.
xv. PP (particulate phosphate)
PP (mg L-1) mean values (Figure III-C48) were similar among
groups; groups B and D had the highest mean values and the largest standard deviations. The
values presented a similar pattern as observed for the other phosphate species.
xvi. Chlorophyll a
Chlorophyll a (pg L-1) mean concentration values were also similar
in pattern to the phosphate -related concentrations across the groups (Figure III-C49). Groups A,
B, and E had lower chlorophyll a (pg L-1) mean values and reduced variability compared to the
higher chlorophyll a (pg L-1) mean values of groups C and D and the largest standard deviation in
group D.
xviii. DOC (Dissolved organic carbon)
DOC (mg L-1) showed variability across the five group means
(Figure III-050). The highest mean values and widest standard deviation were in group D (Figure
III-050).
c. Interannual Variability (Pre- and Post -Mod Alt L Creeks)
Comparisons among pre- and post -Mod Alt L water quality parameters
were made for Jacks Creek, Jacobs Creek, Drinkwater Creek, Tooley Creek, Huddles Cut, Porter
Creek, and DCUT11. To compare interannual variability among these seven creeks, data from
all stations for each parameter were classified as pre -Mod Alt L or post -Mod Alt L (Table III-C1).
Pre- and post -mod Alt-L conditions were compared using a one-way ANOVA and t scores and p-
values are presented in Table III-C4 — III-C10. Differences were considered significant if p-values
were <_ 0.05.
i. Jacks Creek
Jacks Creek showed significant differences for nine of the 17
parameters pre- and post -Mod Alt L; temperature, dissolved oxygen, orthophosphate, and total
dissolved phosphate increased while pH, ammonium, nitrate, particulate nitrogen, and chlorophyll
a decreased (Table III-C4). Chlorophyll a concentration post -Mod Alt L mean continued to be
less than half the pre -mean, an indication of fewer phytoplankton.
ii. Jacobs Creek
Jacobs Creek showed statistically significant differences in eight of
the 17 parameters pre- and post -Mod Alt L (Table III-05). Turbidity, orthophosphate, total
dissolved phosphate, and dissolved organic carbon increased, while salinity, conductivity, pH,
and particulate phosphate concentrations decreased. The nitrogen species presented almost
equally divided among minimal increases and slight decreases but were not significant.
Drinkwater Creek
Drinkwater Creek showed statistically significant differences for ten
of the 17 parameters (Table III-C6). Dissolved Kjeldahl nitrogen, particulate nitrogen,
III-C-10

orthophosphate, total dissolved phosphate, particulate phosphate, chlorophyll a, and DOC
decreased post -Mod Alt L while turbidity, pH, and ammonium increased (Table III-C6). The rest
of the parameters were almost equally divided among slight increases and slight decreases but
were not significant.
iv. Tooley Creek
Tooley Creek showed statistically significant differences pre- and
post -Mod Alt L for nine of the 17 parameters (Table III-C7). Temperature, salinity, conductivity,
nitrate, dissolved Kjeldahl nitrogen, orthophosphate, and total dissolved phosphate increased
whereas turbidity and particulate phosphate decreased. Depth, dissolved oxygen, and ammonium
increased, but not significantly. Total dissolved nitrogen and dissolved organic carbon were not
sampled in the pre -Mod Alt L period for this creek.
v. Huddles Cut
Huddles Cut showed statistically significant differences in nine of
the 17 parameters pre- and post -Mod Alt L; turbidity, nitrate and particulate phosphate decreased,
while temperature, salinity, dissolved oxygen, dissolved Kjeldahl nitrogen, orthophosphate, and
total dissolved phosphate increased post -Mod Alt L (Table III-C8). Ammonium, particulate
nitrogen, and chlorophyll a increased slightly. Total dissolved nitrogen and dissolved organic
carbon were not sampled in the pre -Mod Alt L period for this creek.
vi. Porter Creek
Porter Creek showed statistically significantly increases in depth,
turbidity, pH, ammonium, DKN, particulate nitrogen, total dissolved nitrogen, orthophosphate,
total dissolved phosphate, particulate phosphate, chlorophyll a, and DOC. Among the other five
abiotic parameters, the distribution of increases and decreases was almost evenly distributed
(Table III-C9).
vii. DCUT11
DCUT11 is on its fourth post -Mod Alt L year, and as such the
statistical power for any interpretation continues to be limited. Six parameters showed significant
differences: turbidity, ammonium, and particulate nitrogen decreased, while depth, pH, and DOC
increased for this comparison (Table III-C10).
3.0 Summary and Conclusions
a. Temporal variability
A Principal Components Analysis (PCA) indicated the continuation of the
relationships between the water quality parameters and the seasonal cycle of water quality
variability (Figure III-C1). The PC1 mean value for all stations per month of the historical record
presented two separate groups: negative values during the colder months (January, February,
March, April, November, and December) and positive values during the warmer months. The
mean PC2 values show the opposite pattern. This particular pattern shows stations responded
to biological (i.e., chlorophyll a and DO) and non -conservative biochemical concentrations (e.g.,
nutrient concentrations) during the warmer months when the phytoplankton community is most
active and, in contrast, during colder months responded mostly to conservative elements (e.g.,
salt and pH) as shown in the bi-plot (Figure III-C1).
b. Spatial variability
A cluster analysis revealed five distinct groups for the pre- and post -Mod
Alt L water quality station/years (Figure III-C33). Group A was the second largest group with Duck
III-C-11

Creek, Little Creek, Porter Creek, Broomfield Swamp Creek, and SCUT1 upstream and
downstream stations in Drinkwater Creek, DCUT11, DCUT19, Porter Creek, Duck Creek,
Broomfield Swamp Creek, and SCUT1 (red colored stations in Figure III-C33). This group had a
mix of intermediate values for most water quality parameters compared to other groups, although
it also had the lowest average for pH and particulate nitrogen and the highest depth and nitrate
values (Table III-C3). Group B consisted of upstream station/years in Drinkwater Creek, Huddles
Cut, Jacks Creek, Tooley Creek, and Porter Creek and downstream station/years in Huddles Cut
and DCUT19 (Figure III-C33, green colored group). This group had intermediate values for all
water quality parameters (Table III-C3). Group C (Figure III-C33, blue colored group) was the
smallest group (only one upstream station) in Huddles Cut. This group had highest average
conductivity and the lowest average for depth, temperature, dissolved oxygen, and nitrate values
(Table III-C3). Group D included mostly upstream stations from Huddles Cut and Tooley Creek
and downstream stations in Huddles Cut (Figure III-C33, orange colored group). This group had
the lowest average salinity and conductivity, but the highest turbidity, ammonium, DKN,
particulate nitrogen, total dissolved nitrogen, orthophosphate, total dissolved phosphate,
particulate phosphate, chlorophyll a, and dissolved organic carbon. Group E had most of the
stations of all groups and consisted of Jacobs Creek, Long Creek, and PA2 upstream and Duck
Creek, Jacobs Creek, Jacks Creek, Little Creek, Long Creek, PA2, Tooley Creek, Porter Creek,
and DCUT19 downstream (Figure III-C33; teal colored group). This group had highest average
salinity, temperature, dissolved oxygen, and pH, whereas it had the lowest turbidity, ammonium,
DKN, total dissolved nitrogen, orthophosphate, total dissolved phosphate, particulate phosphate,
chlorophyll a, and dissolved organic carbon concentrations (Table III-C3).
(End of material prepared by Dr. Suelen Tullio)
III-C-12

Component 2 (17.9 %)
1.0
0.5
0.0
- 0.5
- 1.0
Winter
NO3
Fall
Spring
Summer
-1.0 -0.5 0.0 0.5
Component 1 (29.8 %)
1.0
Figure III-C1. Principal Components Analysis biplot of interrelationships among all water quality
variables. Water quality variables are: depth (DEP, in), temperature (TEMP, °C), salinity (SAL),
conductivity (COND, mS), turbidity (TURB, NTU), dissolved oxygen (DO, mg L-1), pH (pH),
ammonium (NH4, mg L-1), nitrate (NO3, mg L-1), dissolved Kjeldahl nitrogen (DKN, mg L-1),
particulate nitrogen (PN, mg L-1), total dissolved nitrogen (TN, mg L-1), orthophosphate (PO4, mg
L-1), total dissolved phosphate (TDP, mg L-1), particulate phosphate (PP, mg L-1), chlorophyll a
(CHL, pg L-1), and dissolved organic carbon (DOC, mg L-1).
III-C-13

BSCWQ1
Date
Figure III-C2. Intra-annual variability of Principal Component
1 and Principal Component 2 over time at Broomfield Swamp
Creek Station BSCWQ1 (upstream). Data collection began in
2019.
BSCWQ2
Uate
Figure III-C3. Intra-annual variability of Principal Component
1 and Principal Component 2 over time at Broomfield Swamp
Creek Station BSCWQ2 (midstream). Data collection began
in 2019.
BSCWQ3
T:tt
Figure III-C4. Intra-annual variability of Principal Component
1 and Principal Component 2 over time at Broomfield Swamp
Creek Station BSCWQ3 (downstream). Data collection began
in 2019.
III-C-14

Jan 11
Figure III-05. Interannual variability of Principal Component
1 and Principal Component 2 over time at SCUT1 station
SC1WQ1 (upstream). Data collection began in 2019.
6
4
2
5C1WQ2
ion-21
Dzte
la 77
Figure III-C6. Interannual variability of Principal Component 1
and Principal Component 2 over time at SCUT1 station
SC1WQ2 (midstream). Data collection began in 2019.
Jam-19
5C1WQ3
Dzt2
la 77
Figure III-C7. Interannual variability of Principal Component 1
and Principal Component 2 over time at SCUT1 station
SC1WQ3 (downstream). Data collection began in 2019.
III-C-15

1wQ1
Figure III-C8. Interannual variability of Principal Component 1 and
Principal Component 2 over time at Jacks Creek station JWQ1
(upstream). The value of the positive data point off the scale is shown.
Vertical line at 2015 separates pre- from post -Mod Alt L.
a
ti
4
2
-2
-4
6
-8
lan-l2 lan-3.i Ian-14 Ian-15
s;
di
JWQ2
lan-16 Jan-17 Jan-18 lan-19 far-20 Jan-21
❑ate
Jan-22
Figure III-C9. Interannual variability of Principal Component 1 and
Principal Component 2 over time at Jacks Creek station JWQ2
(downstream). Vertical line at 2015 separates pre- from post- Mod Alt L.
III-C-16

Ian• 12
Ian-13
1.3n14
1.3n 15
lam 14
lark-17
Date
lan•18
Jan-19
lan•20
lan•21
1an.22
Figure III-C10. Interannual variability of Principal Component 1 and
Principal Component 2 over time at Little Creek station LCWQ1
(upstream).
lark-12
lark-13
Jan • 14
lark15
LC W Q2
Jan-16 1ar-17
Date
lar-18
lan•19
Jan-20
lan•21
Jar-22
Figure III-C11. Interannual variability of Principal Component 1 and
Principal Component 2 over time at Little Creek station LCWQ2
(downstream).
III-C-17

v-1l
1��1a
la�ls
Ian-16
larvl7
Da[e
Ja-18
Jan-14
Jan-20
Jan-21
Jan-22
Figure III-C12. Interannual variability of Principal Component 1 and
Principal Component 2 over time at Jacobs Creek station JCBWQ1
(upstream). Vertical line at 2014 separates pre- from post -Mod Alt L.
—6— PC:
Jcewa,2
n-16 Jan-17
Date
Figure III-C13. Interannual variability of Principal Component 1 and
Principal Component 2 over time at Jacobs Creek station JCBWQ2
(downstream). Vertical line at 2014 separates pre- from post -Mod Alt L
III-C-18

6
-6
-6
PA2WQ1
Jan-12 Jan 13 Jan 1.7 Jan IS Jan 16 Jan-17 Jan-18 Jan-19 Jan-20 Jan-21 Jan22
Date
Figure III-C14. Interannual variability of Principal Component 1 and
Principal Component 2 over time at PA2 station PA2WQ1 (upstream).
G
2
PA2WQ2
—6— PC1
- 4.- PC2
lan-13 Jan•14 fan 11, Jra11 Jan 17
D31c2
Figure III-C15. Interannual variability of Principal Component 1 and
Principal Component 2 over time at PA2 station PA2WQ2 (downstream).
III-C-19

a
6
9
2
m
0 r)
6
-2
.8
lan•12
lan-13
ran -14
Ian-15
fan-16 lan-17
D::te
lan-18
Jan-19
Jan•2O
lan•21
Jan•22
Figure III-C16. Interannual variability of Principal Component 1 and
Principal Component 2 over time at Drinkwater Creek station DVVVVQ1
(upstream). Vertical line at 2013 separates pre- from post -Mod Alt L.
8
.2
- 4
- 6
- 8
Jan-12
lan-13
Jan-14
DWWQ2
Jan-1S Ian-16
Jan-17
Date
Jan-18
Jan-19
Jan-2O
Jan•21
Jan-22
Figure III-C17. Interannual variability of Principal Component 1 and
Principal Component 2 over time at Drinkwater Creek station DVVWQ2
(downstream). Vertical line at 2013 separates pre- from post -Mod Alt L.
III-C-20

-8
Jan-12
Jar-13
Jan-14
Jan-15
lan-16 Date Jan-17
Jan-18
Jarr19
Jan-20
Jar,-21
Jan-22
Figure III-C18. Interannual variability of Principal Component 1 and
Principal Component 2 over time at Long Creek station LOCWQ1
(upstream).
—6— PCI
- , PC2
4
-8
12n-12
r'Y'd 'e3
lan-13
Jan-14
lan-15
Ian-16
LOCWQ2
k is wa
m r^J 'd ' S f
Ck,n
Ian-17 Jan-18
Date
Jan-19
do-
Jan-20
Jan-27.
Jan-22
Figure III-C19. Interannual variability of Principal Component 1 and
Principal Component 2 over time at Long Creek station LOCWQ2
(downstream).
III-C-21

lan-16 Jan•17
Date
Jarv18
lan• 19
lan.2n
Ian 21
Jan-22
Figure III-C20. Interannual variability of Principal Component
1 and Principal Component 2 over time at Tooley Creek station
TWQ1 (upstream west prong). The Y axis separates pre- from
post -Mod Alt L.
8
6
4
-4
-8
TWIN
Jan-12 Jan-13 lan-14 Jan-15 Jan-16 Jan-17 Jan-18 Jan-19 Jan-20 fan-21
Date
!nn-22
Figure III-C21. Interannual variability of Principal Component
1 and Principal Component 2 over time at Tooley Creek station
TWQ2 (upstream east prong). The Y axis separates pre- from
post -Mod Alt L.
8
6
4
d
S 0
•4
-6
-8
Jan12
TWQ3
Jan-13 Jan-14 Jan-15 Jan-16 Jan-17 1an18 Jan-19 Jan-20 Jan-21
Date
Jan-22
Figure III-C22. Interannual variability of Principal Component
1 and Principal Component 2 over time at Tooley Creek station
TWQ3 (downstream). The Y axis separates pre- from post -
Mod Alt L.
III-C-22

Jen•12
Ao-13
16n•14
Jan-15
1an.16
HWR1
Jan-17
Date
16n.16
Jan-19
Jan-20
16 .21
tan-22
Figure III-C23. Interannual variability of Principal Component 1 and
Principal Component 2 over time at Huddles Cut station HWQ1
(upstream west prong). The value of the positive data point off the
scale is shown. Post -Mod Alt began in 2010.
10
6
d
2
-4
-6
a
Jdn 12
HWQ3
9.90
ee
W 'r V 4 /! i r.9 is •
id/N ^ •
+G
9.61
7.94 8.02 8.14
Jan•13 1an•14 .an 15 14n•16 149.17 1,-18 .a^•19 Jan 20 Jan 21
Date
Figure III-C25. Interannual variability of Principal Component 1
and Principal Component 2 over time at Huddles Cut station
HWQ3 (upstream main prong). The value of the positive data
point off the scale is shown. Post -Mod Alt began in 2010.
lan-13
lan•14
1an-15
lan-16 Jan-17
Date
lan-18
lan-19
lan-20
1an•21
Jan-22
Figure III-C24. Interannual variability of Principal Component 1
and Principal Component 2 over time at Huddles Cut station
HWQ2 (downstream west prong). The value of the positive data
point off the scale is shown. Post -Mod Alt began in 2010.
4
2
>
-4
•6 -
.8
Jan•12
+ PQ
Jan 13
ry'
N Ih a''m "
'eri I rn1
f1 'IP'r6 f ry
.;yirAl
it
a!
Jan 14
1an•15
. ar. 16 1en
04te
Jan•19
-11.8.3
lan•20
.an 21
� N
A
Jan 22
Figure III-C26. Interannual variability of Principal Component 1 and
Principal Component 2 over time at Huddles Cut station HWQ4
(downstream main prong). The value of the positive data point off
the scale is shown. Post -Mod Alt began in 2010.
III-C-23

8
6
4
2
w
a 0
-2
-4
6
-8 _.
Jan-12
Jan•13
lan-14
lan-15
PCWQ1
Jan-16 Jan-17
Date
Jan-18
Jan-19
Jar-2D
Jan-21
Jan•22
Figure III-C27. Interannual variability of Principal Component 1 and
Principal Component 2 over time at Porter Creek station PCWQ1
(upstream). The value of the positive data point off the scale is shown.
Vertical line at 2016 separates pre- from post -Mod Alt L.
s
4
2
m
3
lJ 0
-2
-4
-6
-8
Jan-12
Jan-13
Jan•14
lan-15
la n-16
PCWQ2
Jan-17
Date
Jan-18
Jan-19
Jar -2O
Jan-21
Jan-22
Figure III-C28. Interannual variability of Principal Component 1 and
Principal Component 2 over time at Porter Creek station PCWQ2
(downstream). Vertical line at 2016 separates pre- from post -Mod Alt L.
III-C-24

ian 15
San- 16 Ian- ] 7
Date
Jan-/8
Jan-19
Jar-2D
Ian-2/
Jan-22
Figure III-C29. Interannual variability of Principal Component 1 and
Principal Component 2 over time at DCUT11 station DC11WQ1. Data
collection began in 2013. Vertical line at 2018 separates pre- from post -
Mod Alt L.
4
2
w
7
V 0
-2
-4
-G
8
Jan-12
lan-13
lan-14
Ian-15
lan-16 lan-17
❑ate
Jan-16
lan-19
lan-2O
Jan-7l
Jan-22
Figure III-C30. Interannual variability of Principal Component 1 and
Principal Component 2 over time at DCUT19 station DC19WQ1. Data
collection began in 2013.
III-C-25

8
6
4
2
w
2
4c
V 0
- 2
- 4
DKCWQ1
-8
Jan-12 Jan-13 Jar-14
1 Jan-16 Jan-17 Jan-18 Jan-19 Jan•2O Jan•21 Jan-22
Date
Figure III-C31. Interannual variability of Principal Component 1 and
Principal Component 2 over time at Duck Creek station DKCWQ1
(upstream).
G
4
2
a
0
- 2
-4
-6
- 8
Jan-12 Ian 1.3
D KCWQ2
:.i•i 11 :1,1n•17 lan 18 lan.l9 Ian-2O Jan-2/ fan-22
f ;1tq
Figure III-C32. Interannual variability of Principal Component 1 and
Principal Component 2 over time at Duck Creek station DKCWQ2
(downstream).
III-C-26

41-414m
MI 1
,,16�m�i�f�`�`af�d�ml
.._.! .1 a . a�a a x)a3�33 ,. r .a a' °! 4401'3313 c&�Ia� mo t '= agiz l A' r� K A -a; IA,
� � Ea�� � '��
Figure III-C33. Agglomerative, hierarchical cluster analysis of annual means of each water quality parameter at each water quality station (2012-2021). Five distinct clusters of water quality stations were
revealed (A, B, C, D, E).
III-C-27

35
30
25
20
t
Q
m
O 15
10
T
A .. E
Cluster
Figure III-C34. Comparison of mean depth (in) for each
group of water quality stations identified by cluster
analysis. Error bar is 1 standard deviation from the mean.
As cluster C was comprised of only 1 sample, no error bar
is shown.
Temperature (°C)
Cluster
Figure III-C35. Comparison of mean temperature (C) for
each group of water quality stations identified by cluster
analysis. Error bar is 1 standard deviation from the
mean. As cluster C was comprised of only 1 sample, no
error bar is shown.
III-C-28

10
8
4
2
0
Cluster
E
Figure III-C36. Comparison of mean salinity for each group
of water quality stations identified by cluster analysis. Error
bar is 1 standard deviation from the mean. As cluster C was
comprised of only 1 sample, no error bar is shown.
C
Cluster
Figure III-C37. Comparison of mean conductivity (mS) for each
group of water quality stations identified by cluster analysis.
Error bar is 1 standard deviation from the mean. As cluster C
was comprised of only 1 sample, no error bar is shown.
III-C-29

10-
0
T
A B C
Cluster
Figure III-C38. Comparison of mean turbidity (NTU) for each
group of water quality stations identified by cluster analysis.
Error bar is 1 standard deviation from the mean. As cluster C
was comprised of only 1 sample, no error bar is shown.
0
A B C ❑ E
Cluster
Figure III-C39. Comparison of mean dissolved oxygen (mg L-1) for
each group of water quality stations identified by cluster analysis.
Error bar is 1 standard deviation from the mean. As cluster C was
comprised of only 1 sample, no error bar is shown.
III-C-30

a
4-
3-
2-
1-
0
A 8 C
Cluster
Figure III-C40. Comparison of mean pH for each group of water
quality stations identified by cluster analysis. Error bar is 1
standard deviation from the mean. As cluster C was comprised
of only 1 sample, no error bar is shown.
J
E
z
E
7
o
E
F
0.2
0.0
�i.
A
B C
Cluster
E
T.
Figure III-C41. Comparison of mean ammonium (NH4) (mg L-1)
for each group of water quality stations identified by cluster
analysis. Error bar is 1 standard deviation from the mean. As
cluster C was comprised of only 1 sample, no error bar is
shown.
III-C-31

J
0.3 H
m
0
0.0
A
Cluster
Figure III-C42. Comparison of mean nitrate (NO3) (mg L-1) for
each group of water quality stations identified by cluster analysis.
Error bar is 1 standard deviation from the mean. As cluster C
was comprised of only 1 sample, no error bar is shown.
J
E
z
c
2__
z
m 0
1.
v 0.5
a
0.0
T
T
A s D E
Cluster
Figure III-C43. Comparison of mean dissolved Kjeldahl nitrogen
(DKN) (mg L-1) for each group of water quality stations identified
by cluster analysis. Error bar is 1 standard deviation from the
mean. As cluster C was comprised of only 1 sample, no error bar
is shown.
III-C-32

0.0�
T
A
T
0 C D E
Cluster
Figure III-C44. Comparison of mean particulate nitrogen (PN) (mg L-1)
for each group of water quality stations identified by cluster analysis.
Error bar is 1 standard deviation from the mean. As cluster C was
comprised of only 1 sample, no error bar is shown.
3 3.5
E
3.0
z
a
h 2.5
- 2.0
2
iv 1.5-
0
a
1.0-
R
0.5-
0.0
T
A
1
o
Cluster
Figure III-C45. Comparison of mean total dissolved nitrogen (TDN) (mg
L-') for each group of water quality stations identified by cluster analysis.
Error bar is 1 standard deviation from the mean. As cluster C was
comprised of only 1 sample, no error bar is shown.
III-C-33

J
E
0
a
w
•
0.
N
0
s
0
s
0
0.25 -
0.00-• MT.11
•
A B D
Cluster
Figure III-C46. Comparison of mean orthophosphate (PO4) (mg L-1)
for each group of water quality stations identified by cluster analysis.
Error bar is 1 standard deviation from the mean. As cluster C was
comprised of only 1 sample, no error bar is shown.
J
i 71 -
E
a
a
m
s
0
-
o ! .
s
0.50 -
0
;a 0.25 -
a
0.00
B C
Cluster
Figure III-C47. Comparison of mean total dissolved phosphate (TDP)
(mg L-1) for each group of water quality stations identified by cluster
analysis. Error bar is 1 standard deviation from the mean. As cluster C
was comprised of only 1 sample, no error bar is shown.
III-C-34

0.30
1 0.25
d
d
0 0.20
3
0
r
0 0.15
0.00
A
B 0
Cluster
Figure III-C48. Comparison of mean particulate phosphate (PP) (mg L-1)
for each group of water quality stations identified by cluster analysis.
Error bar is 1 standard deviation from the mean. As cluster C was
comprised of only 1 sample, no error bar is shown.
Chlorophyll a (CHL) (ug/L)
100
80
60
40
20 -
0
�I•
1-
A
B C
C1u ster
F
Figure III-C49. Comparison of mean chlorophyll a (Chl a) concentration
(pg L-1) for each group of water quality stations identified by cluster
analysis. Error bar is 1 standard deviation from the mean. As cluster C
was comprised of only 1 sample, no error bar is shown.
III-C-35

T
T
B
Cluster
D E
Figure III-050. Comparison of mean dissolved organic carbon (DOC)
(mg L-1) for each group of water quality stations identified by cluster
analysis. Error bar is 1 standard deviation from the mean. As cluster C
was comprised of only 1 sample, no error bar is shown.
III-C-36

Creek
Impact
Creek?
Pre -Mod Alt L Years
Post -Mod Alt L
Years
Broomfield
Swamp Creek
Y
2019-2021
DCUT11
Y
2013-2017
2018-2021
Drinkwater Creek
Y
20112, 2012
2013-2021
Huddles Cut
y
1999a, 2000-2001, 2002a,
2007-2009
2010-2021
Jacks Creek
Y
1999a, 2000-2001, 2002a,
2003-2005, 20112,
2012-2014
2015-2021
Jacobs Creek
Y
20112, 2012-2013
2014-2021
Porter Creek
Y
20112, 2012-2015
2016-2021
Tooley Creek
y
1999a, 2000-2001, 2002a,
2010-2011
2012-2021
DCUT19
N
2013-2021
Duck Creek
N
20112, 2012-2021
Little Creek
N
20112, 2012-2021
Long Creek
N
20112, 2012-2021
PA2
N
20112, 2012-2021
SCUT1
N
2019-2021
a These years have only partial data but included in the analysis.
III-C-37

Table III-C2. Loading for each water quality variable on each principal component. Positive
values indicate that the variable is positively correlated to the principal component. Negative
values indicate that the variable is negatively correlated to the principa component.
Water quality variable
Principal Component 1
Principal Component 2
Depth (in)
-0.4766
0.1388
Temperature (°C)
0.2355
-0.5326
Salinity
-0.5375
-0.5570
Conductivity (mS)
-0.4028
-0.7063
Turbidity (NTU)
0.6083
0.2227
Dissolved oxygen (mg L-1)
-0.5198
0.2459
pH
-0.4189
-0.4584
Ammonium (NH4; mg L-1)
0.5022
0.3077
Nitrate (NO3; mg L-1)
0.0741
0.6370
Dissolved Kjeldahl nitrogen (DKN; mg L-1)
0.6751
-0.1964
Particulate nitrogen (PN; mg L-1)
0.4044
-0.6280
Total dissolved nitrogen (TN; mg L-1)
0.7605
0.2065
Orthophosphate (PO4; mg L-1)
0.7126
-0.0723
Total dissolved phosphate (TDP; mg L-1)
0.7737
-0.1395
Particulate phosphate (PP; mg L-1)
0.5329
-0.4275
Chlorophyll a (Chl a; pg L-1)
0.3053
-0.6588
Dissolved organic carbon (DOC; mg L-1)
0.7640
0.0316
Table III-C3. Average of water quality parameters across the five groups identified by cluster
analysis on 2012-2021 data (Figure III-C33).
Parameter
Group A
Group B
Group C
Group D
Group E
Number of stations by Group
79
69
1
13
103
Depth (in)
22.96
6.78
6.41
7.07
21.21
Temperature (°C)
18.25
17.42
15.78
18.07
19.44
Salinity
3.67
4.16
4.99
2.74
7.99
Conductivity (mS)
5.80
6.41
570.59
4.32
12.17
Turbidity (NTU)
12.55
14.59
11.23
37.98
5.57
_1
Dissolved oxygen (mg L)
4.21
4.14
3.51
3.73
6.12
pH
6.52
6.59
6.79
6.60
7.16
Ammonium (NH4; mg L-1)
0.17
0.23
0.13
0.62
0.05
Nitrate (NO3; mg L-1)
0.24
0.02
0.00
0.01
0.04
Dissolved Kjeldahl nitrogen (DKN; mg L-1)
0.94
1.36
1.46
2.31
0.80
Particulate nitrogen (PN; mg L-1)
0.25
0.41
0.70
0.88
0.28
Total dissolved nitrogen (TN; mg L-1)
1.10
1.15
1.19
2.34
0.64
Orthophosphate (PO4; mg L-1)
0.08
0.32
0.26
1.01
0.05
Total dissolved phosphate (TDP; mg L-1)
0.13
0.38
0.32
1.00
0.09
Particulate phosphate (PP; mg L-1)
0.08
0.17
0.12
0.18
0.06
Chlorophyll a (Chl a; pg L-1)
15.02
22.76
32.85
59.09
14.75
Dissolved organic carbon (DOC; mg L-1)
16.47
22.39
21.65
33.81
12.36
III-C-38

Table III-C4. Comparison of pre- and post -mod Alt-L conditions for Jacks Creek. Significant
comparisons in bold.
Parameter
Pre-
Mean
Pre- N
Post-
Mean
Post- N
t-ratio
p-value
Depth (in)
16.57
380
15.28
336
1.88
0.06
Temperature (C)
16.97
380
18.48
324
-2.79
0.01
Salinity
4.77
380
4.52
324
0.83
0.41
Conductivity (mS)
7.17
380
7.18
324
-0.01
0.99
Turbidity (NTU)
14.17
367
12.08
324
1.11
0.27
Dissolved oxygen (mg L-1)
4.30
376
4.99
324
-2.86
0.004
pH
6.96
375
6.86
324
2.39
0.02
Ammonium (mg L-1)
0.18
375
0.11
318
1.99
0.05
Nitrate (mg L-1)
0.04
376
0.03
316
2.92
0.004
Dissolved Kjeldahl nitrogen (DKN; mg
L-V )
1.05
370
0.98
321
1.27
0.20
Particulate nitrogen (mg L-1)
0.39
373
0.29
324
3.17
0.002
Total dissolved nitrogen (mg L-1)
0.98
151
0.89
321
0.80
0.43
Orthophosphate (mg L-1)
0.09
376
0.12
324
-2.88
0.004
Total dissolved phosphate (mg L-1)
0.14
376
0.16
324
-2.32
0.02
Particulate phosphate (mg L-1)
0.24
376
0.22
322
0.62
0.54
Chlorophyll a (pg L-1)
32.42
363
14.66
324
2.98
0.003
Dissolved organic carbon (mg L-1)
16.17
151
16.77
321
-1.01
0.31
Table III-05. Comparison of pre- and post -mod Alt-L conditions for Jacobs Creek. Significant
comparisons in bold.
Parameter
Pre-
Mean
Pre- N
Post-
Mean
Post- N
t-ratio
p-value
Depth (in)
16.78
116
18.00
411
-1.79
0.08
Temperature (C)
18.51
116
19.84
411
-1.69
0.09
Salinity
11.35
116
7.27
411
11.72
<0.0001
Conductivity (mS)
16.66
116
11.22
411
11.48
<0.0001
Turbidity (NTU)
2.80
116
8.91
411
-4.01
<0.0001
Dissolved oxygen (mg L-1)
5.90
116
6.24
411
-0.91
0.37
pH
7.24
116
7.10
411
2.74
0.007
Ammonium (mg L-1)
0.04
116
0.04
403
0.49
0.62
Nitrate (mg L-1)
0.03
116
0.02
401
1.05
0.30
Dissolved Kjeldahl nitrogen (DKN; mg
L-1)
0.90
112
0.85
403
1.81
0.07
Particulate nitrogen (mg L-1)
0.29
114
0.28
409
0.50
0.62
Total dissolved nitrogen (mg L-1)
0.62
106
0.64
409
-0.82
0.41
Orthophosphate (mg L-1)
0.05
116
0.07
409
-3.12
0.002
Total dissolved phosphate (mg L-1)
0.08
116
0.10
409
-2.86
0.005
Particulate phosphate (mg L-1)
0.08
116
0.06
407
3.78
0.0002
Chlorophyll a (pg L-1)
15.84
116
15.08
405
0.38
0.70
Dissolved organic carbon (mg L-1)
12.24
106
13.32
409
-1.93
0.05
III-C-39

Table III-C6. Comparison of pre- and post -mod Alt-L conditions for Drinkwater Creek. Significant
comparisons in bold.
Parameter
Pre-
Mean
Pre- N
Post-
Mean
Post- N
t-ratio
p-value
Depth (in)
9.74
66
10.54
426
-1.40
0.16
Temperature (C)
17.42
66
17.60
419
-0.22
0.83
Salinity
5.37
66
4.09
419
1.86
0.07
Conductivity (mS)
7.88
66
6.22
419
1.74
0.09
Turbidity (NTU)
4.68
66
7.17
419
-3.02
0.003
Dissolved oxygen (mg L-1)
3.74
66
3.59
419
0.46
0.65
pH
6.40
66
6.54
419
-2.01
0.05
Ammonium (mg L-1)
0.07
66
0.11
411
-3.18
0.002
Nitrate (mg L-1)
0.01
66
0.02
409
-0.47
0.64
Dissolved Kjeldahl nitrogen (DKN; mg
L-1)
1.22
64
1.06
411
3.15
0.002
Particulate nitrogen (mg L-1)
0.34
66
0.26
415
2.04
0.05
Total dissolved nitrogen (mg L-1)
0.88
50
0.89
416
-0.02
0.98
Orthophosphate (mg L-1)
0.29
66
0.22
417
2.04
0.04
Total dissolved phosphate (mg L-1)
0.35
66
0.26
417
2.23
0.03
Particulate phosphate (mg L-1)
0.13
66
0.08
415
4.26
<0.0001
Chlorophyll a (pg L-1)
26.85
65
14.42
415
2.68
0.01
Dissolved organic carbon (mg L-1)
28.01
50
20.21
416
3.00
0.004
Table III-C7. Comparison of pre- and post -mod Alt-L conditions for Tooley Creek. Significant
comparisons in bold.
Parameter
Pre-
Mean
Pre-
N
Post-
Mean
Post- N
t-ratio
p-value
Depth (in)
11.28
305
11.82
682
-0.91
0.36
Temperature (C)
16.61
307
17.69
664
-2.00
0.05
Salinity
5.52
307
6.38
665
-2.67
0.008
Conductivity (mS)
8.27
303
9.61
665
-2.81
0.005
Turbidity (NTU)
16.36
296
8.74
664
3.90
0.0001
Dissolved oxygen (mg L-1)
4.43
301
4.70
662
-1.06
0.29
pH
7.02
298
6.80
665
1.31
0.19
Ammonium (mg L-1)
0.11
306
0.12
657
-0.95
0.34
Nitrate (mg L-1)
0.02
306
0.03
655
-2.10
0.04
Dissolved Kjeldahl nitrogen (DKN; mg
L-1)
1.09
305
1.20
653
-2.82
0.005
Particulate nitrogen (mg L-1)
0.32
302
0.32
660
-0.38
0.70
Total dissolved nitrogen (mg L-1)
No data
0
0.94
661
Orthophosphate (mg L-1)
0.24
306
0.28
665
-2.42
0.02
Total dissolved phosphate (mg L-1)
0.29
306
0.33
664
-2.26
0.02
Particulate phosphate (mg L-1)
0.28
306
0.11
659
13.04
<0.0001
Chlorophyll a (pg L-1)
18.30
295
15.88
658
1.41
0.16
Dissolved organic carbon (mg L-1)
No data
0
20.06
661
III-C-40

Table III-C8. Comparison of pre- and post -mod Alt-L conditions for Huddles Cut. Significant
comparisons in bold.
Parameter
Pre-
Mean
Pre-
N
Post-
Mean
Post- N
t-ratio
p-value
Depth (in)
6.51
507
6.90
1093
-1.87
0.06
Temperature (C)
15.47
505
18.73
1084
-7.33
<0.0001
Salinity
2.70
503
4.73
1083
-12.06
<0.0001
Conductivity (mS)
4.09
502
17.29
1080
-1.33
0.18
Turbidity (NTU)
28.16
489
22.29
1089
2.19
0.03
Dissolved oxygen (mg L-1)
3.40
488
4.07
1084
-4.62
<0.0001
pH
6.76
490
6.71
1083
1.48
0.14
Ammonium (mg L-1)
0.35
505
0.39
1083
-1.21
0.23
Nitrate (mg L-1)
0.02
505
0.01
1075
1.99
0.05
Dissolved Kjeldahl nitrogen (DKN; mg
L-1)
1.49
503
1.72
1074
-3.91
<0.0001
Particulate nitrogen (mg L-1)
0.54
503
0.62
1085
-1.91
0.06
Total dissolved nitrogen (mg L-1)
No data
0
1.52
933
Orthophosphate (mg L-1)
0.41
505
0.56
1089
-5.32
<0.0001
Total dissolved phosphate (mg L-1)
0.47
505
0.59
1088
-4.31
<0.0001
Particulate phosphate (mg L-1)
0.31
505
0.16
1084
9.66
<0.0001
Chlorophyll a (pg L-1)
33.63
494
37.78
1078
-1.12
0.26
Dissolved organic carbon (mg L-1)
No data
0
25.38
933
Table III-C9. Comparison of pre- and post -mod Alt-L conditions for Porter Creek. Significant
comparisons in bold.
Parameter
Pre-
Mean
Pre- N
Post-
Mean
Post- N
t-ratio
p-value
Depth (in)
18.10
209
22.99
287
-4.14
<0.0001
Temperature (C)
17.15
209
17.48
283
-0.49
0.62
Salinity
2.57
209
2.92
283
-0.98
0.33
Conductivity (mS)
4.72
209
4.62
283
0.14
0.89
Turbidity (NTU)
9.39
209
21.87
283
-5.56
<0.0001
Dissolved oxygen (mg L-1)
4.08
207
3.83
283
0.89
0.38
pH
6.24
209
6.55
283
-5.99
<0.0001
Ammonium (mg L-1)
0.14
201
0.22
281
-2.73
0.007
Nitrate (mg L-1)
0.12
207
0.06
275
1.79
0.07
Dissolved Kjeldahl nitrogen (DKN; mg
L-1)
0.81
199
1.07
281
-5.27
<0.0001
Particulate nitrogen (mg L-1)
0.26
205
0.36
283
-3.00
0.003
Total dissolved nitrogen (mg L-1)
0.80
205
1.01
283
-4.18
<0.0001
Orthophosphate (mg L-1)
0.07
207
0.14
283
-6.49
<0.0001
Total dissolved phosphate (mg L-1)
0.14
207
0.19
283
-4.24
<0.0001
Particulate phosphate (mg L-1)
0.10
207
0.13
281
-2.23
0.03
Chlorophyll a (pg L-1)
13.66
203
22.71
284
-2.71
0.007
Dissolved organic carbon (mg L-1)
15.43
205
17.80
283
-3.50
0.0005
III-C-41

Table III-C10. Comparison of pre- and post -mod Alt-L conditions for DCUT11. Significant
comparisons in bold.
Parameter
Pre-
Mean
Pre- N
Post-
Mean
Post- N
t-ratio
p-value
Depth (in)
18.53
129
20.45
104
-2.53
0.01
Temperature (C)
17.56
129
18.21
104
-0.59
0.56
Salinity
4.67
129
4.98
104
-0.60
0.55
Conductivity (mS)
7.20
129
7.70
104
-0.67
0.51
Turbidity (NTU)
7.77
129
4.96
104
3.66
0.0003
Dissolved oxygen (mg L-1)
4.25
128
4.47
104
-0.55
0.58
pH
6.33
129
6.58
104
-4.28
<0.0001
Ammonium (mg L-1)
0.06
124
0.04
104
2.17
0.03
Nitrate (mg L-1)
0.01
124
0.01
103
-1.02
0.31
Dissolved Kjeldahl nitrogen (DKN; mg L-
1)
0.73
123
0.75
104
-0.37
0.71
Particulate nitrogen (mg L-1)
0.22
127
0.18
104
2.10
0.04
Total dissolved nitrogen (mg L-1)
0.65
128
0.72
104
-1.65
0.10
Orthophosphate (mg L-1)
0.04
128
0.03
104
1.13
0.26
Total dissolved phosphate (mg L-1)
0.08
128
0.07
104
1.46
0.15
Particulate phosphate (mg L-1)
0.05
127
0.04
104
1.48
0.14
Chlorophyll a (pg L-1)
10.35
125
10.46
103
-0.04
0.97
Dissolved organic carbon (mg L-1)
15.50
128
17.57
104
-2.36
0.02
III-C-42