Final project report submitted to Iowa Nutrient Research · PDF file · 2016-04-281...
Transcript of Final project report submitted to Iowa Nutrient Research · PDF file · 2016-04-281...
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Final project report submitted to Iowa Nutrient Research Center
February 13, 2016
Distribution, transport, and biogeochemical transformations of agriculturally derived
nitrogen and phosphorus in Cedar River watershed
Mohammad Iqbal, Professor of Geology and Environmental Science, Department of Earth
Science, University of Northern Iowa, Cedar Falls, IA 50614 ([email protected]; 319-273-2998)
INTRODUCTION
This is the final project report (year 1 and 2 combined). The primary objective of this
study was to calculate nitrogen (N) and phosphorus (P) loading from farmlands within the Cedar
River watershed during the period 2013 - 2015. Additionally, temporal and spatial distributions
of nutrients were studied. The project was conducted in two phases. During phase 1, the highly
agricultural part of the watershed from Charles City to LaPorte City was studied by sampling 18
sites (sites 1-18). During phase 2, additional 10 sites were sampled from Brandon to the last
point in Cedar River at Columbus Junction, Iowa (sites 19-28). Data from both Phase 1 (Figures
1 - 48) and Phase 2 (Figures 49 - 62) are presented in this report with separate descriptions of
important observations. This is to be noted that Phase 1 activities comprise most part of the
project since the intensely agricultural sub-watersheds are in this area.
Data online:
We have uploaded all data from Phase 1 and Phase 2 to our hydrology website for public
viewing and comments. There are google interactive maps that show the watershed areas and
sites 1 through 24. Please go to www.uni.edu/hydrology and click water quality data under Cedar
River Monitoring Plan (see Local Hydrologic data Collection to the right side of the page). Click
each site number to see the details of that site. Click past data to review all data for the site.
There is also a limited graphing capability added (click Graphical data). At this time the temporal
variation in each parameter can be seen. We expect to add more graphical capability over time.
The long term goal of the online posting is to allow the public to see the interrelationships of
water quality parameters and understand the overall hydrologic characteristics of the watershed.
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The uploaded data should be considered as unofficial since we are still experimenting with the
website functionality. We are accepting public comments on posted data.
PROJECT ACTIVITIES
Phase 1 study (2013-14)
During Phase 1, total 18 sites have been sampled once a week from April 5 through
October 31 of 2014. All lab analyses have been completed in the hydrology lab of the
Department of Earth Science, University of Northern Iowa. Time sensitive parameters were
analyzed at the field sites with portable sensors. A set of 48 graphs (Fig 1 – 48) have been
attached to this report that represent our data from phase 1. Based on the obtained data, we
developed sub-watershed maps around each sampling site. We also gathered published land use
information for the watershed to research into nutrient mass balance for the area. When
necessary, data were compiled to produce spatial distribution maps by using GIS mapping tools.
The sampling team went out to the area for sampling as soon as the fields were exposed from
snow cover.
All 18 sites were sampled once a week for stream water and sediments from the
beginning of April to the end of October, 2014. These 18 sites are located all the way from
Charles City to LaPorte City, Iowa covering the main channel Cedar, Little Cedar River, Shell
Rock River, West Fork Cedar River, Black Hawk Creek, and Wolf Creek. A base map is
attached to this report (Fig. 1). From each site, thirty (30) sets of samples were collected and
analyzed for total dissolved solids (TDS), total suspended solids (TSS), dissolved oxygen (DO),
turbidity, total phosphorus (TP), and dissolved nitrogen. Each set of sampling involved over 250
miles of driving in the study area. To ensure efficient sampling, the 18 sites were divided into
two groups (Group A and Group B). Group A included sites 1 through 9 comprising the areas
from Cedar Falls further north to Charles City and Group B included sites 10 through 18 from
Cedar Falls further south to LaPorte City. Two student assistants were given the responsibilities
to do the sampling on the same day where they followed identical field methods. Each time the
same sensing probes were used per site to make sure the data were consistent. These two
students are Sushil Tuladhar, a graduate student in Geography, and Kevin Rupp, an
undergraduate student in Earth Science. Sushil Tuladhar has largely coordinated this project by
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way of field work, lab analysis, and data compilation. Two other undergraduate students,
Madison Pike and Ashly Lembke were involved in gathering land use data from the area. All
students received appropriate training on sampling protocol and lab analytical procedure.
Key Observation:
(1) Baseline: Toward the beginning of the project (October to December, 2013), several sites in
the watershed were sampled for baseline data on N, TP, chloride, sulfate, TDS and TSS. The
baseline data for phosphorus in bottom sediments ranged from 122.6 to 543.5 µgP/gm of dry wt.
The highest value was observed in Beaver Creek. All other sites had comparable TP values. TP
in baseline water samples ranged from 14 to 185 µg/L. Dissolved NO3-N in all sites were below
4.2 mg/L. In general, all baseline parameters showed stable values as expected in off season
samples.
(2) Seasonal trends: Figures 2 – 21 are attached to this report to portray the observed data on
multiple parameters from April through the end of October, 2014. The graphs show temporal and
spatial trends in TSS, TP and N. As expected, the actual loads of TSS, TP and N during the
growing season are considerably higher than the baseline.
The average distribution of TSS within the watershed is shown in figures 2 through 6.
Most sites show initial high loads of TSS in April and early May and then it appears to peak
again in late June and July. The first rush of TSS can be attributed to the snow melt episodes
causing soil loss from the agricultural fields that are not adequately covered by crops. This is
more prominent in the intensely farmed northern part of the watershed (Fig. 2). According to the
water clarity criteria in the Midwestern streams, 20 mg/L is considered clear and levels higher
than 80 mg/L is considered cloudy. In reference to these levels, the upper reaches of the Cedar
River watershed have exceedingly high TSS during the early season (average 116.5 mg/L). The
average drops to 59 mg/L further south of Cedar Falls/Waterloo where the percentage of
agricultural lands is much lower. Also, the southern part of the study area is characterized by
lower drainage density. The second TSS peaks are attributed to the rain events during the mid-
summer to mobilize field soils. High surface runoff is expected to be the primary cause of soil
loss from the fields. Flash flooding associated with intense rain events can bring large pulses of
eroded soils to the watershed. The area had 5.02 inches of rain that fell from June 16th
through
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the 19th
. The data collected on June 21st showed a rise in average TSS concentration from 30
mg/L to 71 mg/L (sites 1 – 9) toward the northern part of the study area (Fig. 2). From sites 10 -
18 further south the average jumped from 23 mg/L to 122 mg/L (Fig. 3). The average TSS loads
during the mid-season appear to be much higher in the downstream areas (187 mg/L, Fig 3). This
is probably because the farm fields in the north by then are more stabilized with crops to prevent
soil erosion.
Figures 7 – 14 show temporal and spatial trends in total phosphorus (TP) during the early,
middle and late seasons. Loads of TP directly correlate with the transport of TSS in the
watershed during the entire sampling period. Phosphorus is heavily adsorbed to soil particles and
is transported to the streams with eroded soils. This reiterates the importance of soil conservation
practices to achieve the ultimate goals of nutrient reduction. The 4-day intense rains (discussed
above) prior to the 6/21 sampling resulted in 134% and 142% increases in the TP loads over the
northern (sites 1 – 9) and the southern (sites 10 – 18) parts of the area, respectively (Fig. 7, 8).
After the month of July, even though the concentrations of TSS did not show any significant
variations the TP values consistently went up through the early part of September. It could be
due to one of several reasons. It could be the incoming soluble reactive phosphorus (SRP) from
groundwater through base flow. Many streams in the U.S. reportedly have high SRP
concentrations in groundwater during the fall when soils are relatively warm and dry. The high
SRP could be caused by mineralization and accumulation of phosphorous through the summer.
Also, applied manure in areas where water table is shallow could result in higher SRP in
groundwater, which eventually discharges into the streams. This issue needs to be further
investigated by additional sampling of groundwater and conducting source inventories.
Alternatively, the increase of TP might be due to the slow release of phosphorus from the stream
bed sediments to the water column. In the fall, high loads of plant leaves as well as residual
organic debris to the streams can cause the water to turn low in oxygen through the organic
decay process. In anoxic condition, some minerals that adsorb phosphorus can dissolve, thereby
releasing excess P to the water column. All 18 sites showed average TP concentrations
exceeding the 100 µg/L maximum contaminant level (MCL) as recommended by the USEPA for
surface water (Fig. 11). The 3-week plot in Fig. 12 shows a dramatic influx of TP to the streams
in response to the 5 inch rain that fell from June 16th
through the 19th
. The loads of TP in
tons/day are shown in Figures 13 and 14. The TP loads measured at 11 sites where discharge
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data are available from USGS stream-gaging stations range from 0.005 tons/day at Site 15
(Black Hawk Creek at Hudson) on October 10, 2014 to 34 tons/day at Site 12 (Cedar River @
Cedar Falls) on June 21, 2014. The average TP loads of these 11 sites is 1.06 tons/day. With this
rate, the estimated total load of phosphorus in the watershed from the beginning of April through
the end of October (7 months) is 223 tons. Spatial distribution of TP concentrations and loads
over these 11 sites are shown in Fig. 24 and 25. Detailed TP load calculations are shown in Fig.
35.
Spatial and temporal distributions of NO3-N are shown in Fig. 15 through 23. Because
nitrogen is highly soluble in water, influx of nitrogen at all sites are more episodic than
phosphorus (Fig 15 and 16). Strong pulses of nitrogen are primarily associated with rain events
causing higher levels of dissolved nitrogen in the streams. This includes immediate surface
runoff and baseflow. It is also important to understand that a well-integrated system of drainage
tiles below the farm fields offers a favorable condition for nitrogen pulses to the streams. In
general, nitrogen loads are high from early to mid-summer due to the rapid conversion of
fertilizer nitrogen into nitrate before the crops enter the period of maximum uptake. The levels of
nitrogen start to rise again toward the later part of fall. This is primarily derived from the residual
organic nitrogen converting into nitrate through the process of nitrification (Fig 17 and 18). The
high nitrogen levels in the fall are also due to the fact that nitrogen uptake by crops is
considerably reduced by mid to late August. Nitrogen loads in the watershed range from 0.25
tons/day at site 15 (Black Hawk Creek in Hudson) on October 10, 2014 to 1061 tons/day at site
13 (Cedar River at Waterloo) on June 21, 2014 (Fig 20 and 21). The highest load was observed
immediately after the 5 inch rain from June 16 – 19 as discussed in the previous section. This is
an intriguing example how a large fraction of the available nitrogen can be lost from the
agricultural fields as a result of intense rain events, especially in mid-season when the nutrient
would be otherwise used up in crop yield. The average nitrogen load of the 11 sites where
discharge data are available is 45 tons/day. With this rate, the total load of nitrogen in the
watershed from the beginning of April through the end of October is 9450 tons. The relative
distribution of nitrogen in the watershed during early, middle and late seasons are shown in
figure 22. The mid-season concentrations are considerably higher than the other two seasons.
Given that the fields are already in their maximum uptake mode, these high loads in the mid-
season reiterate the urgent need for best management practices in the area. In terms of
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concentration levels, sites 3, 4, and 5 along the Shell Rock River show the lowest amounts of
nitrogen moving through the streams. Fig. 23 shows the spatial distributions of NO3-N loads (in
red circles) at the 11 sites where discharge data are available from the USGS stream gaging
stations. From sampling site 1 through 13, the total nitrogen loads along the main course of the
river gradually increase downstream. Detailed N load calculations are shown in Fig. 34.
(3) Phosphorus loading and rainfall: Phosphorus shows three definite periods of influx into the
river that coincides with the early, middle and late seasons. These three phases of high P loads
directly correlate with the seasonal rain events in the area. In the attached graphs (Fig. 26 – 29),
P transport from some of the heavily farmed areas is compared with the rainfall observed at the
nearest weather stations. When the P concentrations are compared with the concentrations of
total suspended solids (TSS) in the river, direct correlations are observed. P is heavily adsorbed
to soil particles and is transported to the streams with eroded soils. During early and mid-season,
TSS is the primary vehicle for P to move from the agricultural fields to the watershed. However,
a close observation reveals that the primary mechanism of P transport changes during the late
season. After the month of July, even though the concentrations of TSS continue to drop with
minor pulses, the TP values consistently go up through the beginning of September (Fig. 30). It
is attributed to the incoming soluble reactive phosphorus (SRP) from groundwater through base
flow. During the fall when soils are relatively warm and dry, streams receive high levels of SRP.
Also, applied manure in areas where water table is shallow could result in higher SRP in
groundwater. Fig. 31 – 33 show spatial distribution of P, N and TSS in the study area. The data
are average concentrations per site over the entire period of phase 1 study.
(4) Nutrient loading per sub-watershed: Figure 38 shows the 13 sub-watersheds delineated within
the study area based on hydrologic characteristics. Fig. 39 – 42 show nutrient loss from 7 sub-
watersheds that form the primary system of tributaries and directly contribute N and P to the
main course of the Cedar River. The contributing sub-watersheds are Little Cedar River, Cedar
River above Charles City, Shell Rock River, West Fork Cedar River, Beaver Creek, Black Hawk
Creek and Wolf Creek. The calculated average stream output of NO3-N is 22 lbs/acre (Fig. 39),
ranging from 16 to 30 lbs/ac. The total loss of NO3-N from these 7 contributing sub-watersheds
has been calculated as 33,500 tons/yr (i.e., from early April to late Oct). This load is 16.7% of
the state’s total stream output of N reported by Libra, Wolter and Langel in their 2004 nutrient
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budget report (Fig. 40). The calculated average loss of P is 0.41 lbs/acre (Fig. 41), ranging from
0.28 to 0.48 lbs/ac. The total loss of P from the area has been calculated as 646 tons for the year
(Fig. 42). This load is 6% of the state’s total stream output of P reported by Libra, Wolter and
Langel (2004). For detailed calculations of loss per acreage, total stream output and loss
comparison among NO3-N, TP and TSS, refer to Fig. 34 – 37. Temporal and spatial distributions
of phosphorus in stream sediments are shown in Fig. 43 – 46. Both upstream (sites 1-9) and
downstream (sites 10-18) locations show high loading of P in bottom sediments during April and
early May which then drops in June and July. After the month of July, the upstream sites show
relatively low and constant movement of sediment P whereas the downstream sites show a
gradual increase in loads until the beginning of October. Considering all 18 sites in phase 1,
movement of TSS in the stream is moderately correlated with TP, but not with phosphorus in
bottom sediments (Fig. 47).
Phase 2 study (2014-15)
Phase 2 of the project was conducted from early April to late October, 2015. We selected
ten (10) new sites (S19 through S28) in Brandon, Vinton, Urbana, Palo, Marion, Cedar Rapids,
Cedar Bluffs, West Branch, Conesville, and Columbus Junction, Iowa. Sites 23 (Indian Creek,
Marion) and 26 (Hoover Creek, West Branch) are on two tributaries of Cedar River. The rest of
the sites are on the main channel. We have sampled sites 19 - 24 once every 2 weeks and sites
25-28 every 3 weeks from April 4 through October 30. Stream bed sediments have also been
collected from these sites every 3rd
week. Data have been gathered for nitrogen, total suspended
sediments (TSS), temperature, pH, total dissolved solids, conductivity, dissolved oxygen and
total phosphorus (both water and stream sediments). The data from these 10 new sites were done
to finish the project and get a more complete picture of nutrient loading in the Cedar River
watershed. However, the farmed acreage in phase 2 study area is much smaller than the areas
covered in phase 1. Most of our data analysis and investigations in this project were focused on
the work performed during phase 1. The data discussed in this section primarily deal with
observation made over sites 19 – 24. The sites further south of Cedar Rapids (sites 25 – 28) are
far away and beyond the scope of this project. For these 4 sites, we have provided some basic
data in a table at the end of the report.
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Figure 48 shows the sampling locations during the second phase of the project. Each site
was visited for their accessibility, making sure that they were close to a bridge for sampling
convenience. Water and sediment sample analyses were done in the hydrology lab at UNI.
Discharge data are taken from the published USGS records. Each site has been defined based on
the surrounding land use characteristics, topography, and soil types. Mass calculations of TSS,
TP and NO3-N were done for sites 20, 22, 23 and 24.
Key observation:
(1) TSS loading: Fig. 49 - 50 show the temporal and spatial variations in the total suspended
solids (TSS) observed in the stream. In general, from Brandon all the way downstream to Cedar
Rapids the sites show spatially uniform concentrations of TSS. This is unlike what we found
during phase 1 study where sites showed considerable spatial variations at a given time of
sampling. The sub-watersheds studied during phase 1 are characterized by most intensive
agricultural activities in the watershed. Relatively high rate of soil erosion as well as variable
conservation practices along the waterways is attributed to this difference in the average TSS
distribution between phase 1 and 2. Temporally, the TSS value shows the highest average during
mid-June (192 mg/L, Fig. 49). Figure 51 shows the detailed calculations of TSS as per daily
loads and loss per acreage.
(2) TP loading: Temporal distribution of total phosphorus (TP) shows sharp rise in concentration
at different times (Fig. 52). Some of these peaks correspond with rainfall events while others do
not. The relative increase in TP during the late season is attributed to the incoming soluble
reactive phosphorus (SRP) from groundwater through baseflow. SRP in U.S. streams are known
to form through mineralization of dry, P-loaded soils and applied manures. Frequently, SRP
forms in shallow aquifers, which eventually discharges into the streams. The details of SRP
mechanism have been discussed in the previous sections of this report (i.e., phase 1). The early
season peaks in TP that are not linked to rainfall events could be the result of the application
patterns. It is not clear how much of the TP from bottom sediments would be a factor in such a
well oxygenated stream system. Detailed calculations of TP loads at selected sites are shown in
Fig. 54.
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(3) NO3-N loading: Figures 55 and 56 show the distribution of nitrate-nitrogen at six sites from
Brandon to Cedar Rapids. In addition to the nitrogen pulse during April application, increased
concentrations were observed during late May, early June and early July. Even though the plant
uptake is expected to be high during these time periods, especially during May and early June,
the high levels of dissolved N seem to be associated with rain events. Nitrogen is highly soluble,
so rainfall can trigger rapid loss of N from the agricultural fields. In addition to the applied
fertilizers during the early season, parts of the organic nitrogen from the previous year are
subject to nitrification as the soil gets higher moisture content. The late June (6/28) sampling
shows much lower concentrations of N, which is attributed to the high plant uptake along with
low rainfall amounts. Site 23 (Indian Creek at Marion) shows the highest fluctuations in nitrogen
concentrations, ranging from 2.12 mg/L on June 28 to 23.58 mg/L on June 13 (Fig. 55, 56).
Figure 57 shows the details of NO3-N calculations at sites 20, 22, 23 and 24. The average N
loads vary from 3.3 tons/day at site 23 (Indian Creek at Marion) to 152.8 tons/day at site 24
(Cedar River at Cedar Rapids). When compared to their sub-watershed areas, the N loads from
April through October range from 13.58 lbs/acre at site 20 (Cedar River at Vinton) to 32.01
lbs/acre at site 23 (Indian Creek at Marion). Load comparison per acreage for N, TP and TSS is
shown in Fig. 58. Additionally, TP-TSS relationships are presented in Fig. 59-61. Data show
TSS as the primary vehicle for the loss of TP from agricultural fields. Fig. 62 shows data
recorded at sites 25, 26, 27 and 28 during early, middle and late seasons of 2015.
Reference:
R.D. Libra, C.F. Wolter and R.J. Langel, 2004. Nitrogen and phosphorus budgets for Iowa and
Iowa watersheds. Iowa Geological Survey, Technical Information Series 47, Iowa Department of
Natural Resources, 43 p.
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Figure 1: Phase 1 sampling locations (sites 1 – 18)
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Figure 2: Temporal distributions of total suspended solids (TSS) at sites 1 through 9 (Group A)
29.45
35.23
116.51
43.06
45.98
24.01
24.02
20.24
47.32
29.92
71.00
57.25
36.57
33.18
25.85
26.82
27.06
18.85
22.80
23.18
24.54
37.15
19.38
10.90
7.30
10.28
5.47
13.42
6.24 2.76
0
20
40
60
80
100
120
140
1
10
100
1000
Aver
age
Con
cen
trat
ion
(m
g/L
)
Log C
on
cen
trat
ion
(m
g/L
) Temporal distributions of TSS (Group A sites)
CedarRiver@ Charles City LittleCedarRiver near Ionia ShellRockRiver@ Marble Rock ShellRockRiver@ Marble Rock
ShellRockRiver@ Shell Rock WestForkCedarRiver near Kesley WestForkCedarRiver@ Finchford CedarRiver@ Waverly
CedarRiver@ Janesville Average
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Figure 3: Temporal distributions of TSS at sites 10 through 18 (Group B)
25.62
31.39
37.29
59.45
23.06
36.60
26.72
28.79
51.08
22.93
121.85
186.56
71.99
51.00
29.19 22.44
22.88
18.37
22.21
20.99
20.88 26.72
13.78 10.30
7.81 8.64
5.98
29.87
12.82
6.37
0
20
40
60
80
100
120
140
160
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1
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1000
Aver
age
Con
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(m
g/L
)
Log C
on
cen
trat
ion
(m
g/L
) Temporal distributions of TSS (Group B sites)
BeaverCreek@ New Hartford BeaverCreek@ Cedar Falls CedarRiver@ Cedar Falls CedarRiver@ Waterloo
BlackHawkCreek@ Waterloo BlackHawkCreek@ Hudson CedarRiver@ Gilbertville WolfCreek near Dysart
CedarRiver near La Porte City Average
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Figure 4: Spatial distributions of TSS at sites 1 through 9 (Group A)
1
10
100
1000
Cedar
River@CharlesCity
Little Cedar River
near Ionia
Shell Rock
River@MarbleRock
Shell Rock River
near Clarksville
Shell Rock@Shell
Rock
West Fork Cedar
River near Kesley
West Fork Cedar
River@Finchford
Cedar
River@Waverly
Cedar
River@Janesville
Log C
on
cen
trat
ion
(m
g/L
) Spatial distributions of TSS (Group A sites)
4/5 4/19 4/25 5/3 5/10 5/17 5/26 6/1 6/8 6/15 6/21 6/28 7/5 7/12 7/19
7/26 8/2 8/9 8/17 8/23 8/29 9/5 9/12 9/19 9/26 10/3 10/10 10/15 10/25 10/31
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Figure 5: Spatial distributions of TSS at sites 10 through 18 (Group B)
1
10
100
1000
Beaver Creek@New
Hartford
Beaver
Creek@Cedar Falls
Cedar River@Cedar
Falls
Cedar
River@Waterloo
Black Hawk
Creek@Waterloo
Black Hawk
Creek@Hudson
Cedar
River@Gilbertville
Wolf Creek near
Dysart
Cedar River near La
Porte City
Log C
on
cen
trat
ion
(m
g/L
) Spatial distributions of TSS at sites 10 through 24 (Group B sites)
4/5 4/19 4/25 5/3 5/10 5/17 5/26 6/1 6/8 6/15 6/21 6/28 7/5 7/12 7/19
7/26 8/2 8/9 8/17 8/23 8/29 9/5 9/12 9/19 9/26 10/3 10/10 10/15 10/25 10/31
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Figure 6: Average TSS concentrations at all sites during phase 1 (April – October, 2014)
0
30
60
90
120
Ced
ar R
iver
@C
har
les
Cit
y
Ced
ar R
iver
@W
aver
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@Ja
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iver
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edar
Fal
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Ced
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ater
loo
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ilber
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ock
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ear
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rksv
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Shel
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@S
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ock
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esle
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Wes
t F
ork
Ced
ar R
iver
@F
inch
ford
Bea
ver
Cre
ek@
New
Har
tford
Bea
ver
Cre
ek@
Ced
ar F
alls
Bla
ck H
awk C
reek
@W
ater
loo
Bla
ck H
awk C
reek
@H
udso
n
Wolf
Cre
ek n
ear
Dysa
rt
Main River Tributaries
Co
nce
ntr
atio
ns
(mg/L
) Average TSS Concentrations
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Figure 7: Temporal variations in total phosphorus (TP) at sites 1 through 9 (Group A)
0%
-40%
20%
-19% -21%
0%
-47%
47%
55%
-19%
134%
-39%
-2%
-6%
-18%
-2%
-27%
11%
2%
34%
2%
68%
-36%
-15%
3%
-39%
-20%
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-2%
-11%
-60%
-40%
-20%
0%
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160%
0
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250
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400
450
500
Con
cen
trat
ion
s (µ
g/L
)
Temporal distributions of Total Phosphorus at sites 1 through 9 (Group A sites)
Cedar River@Charles City Little Cedar River near Ionia Shell Rock River@Marble Rock Shell Rock River near Clarksville
Shell Rock@Shell Rock West Fork Cedar River near Kesley West Fork Cedar River@Finchford Cedar River@Waverly
Cedar River@Janesville %change
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Figure 8: Temporal variations in total phosphorus (TP) at sites 10 through 18 (Group B)
0%
-26%
-16%
1%
-12%
7%
-34%
32% 32%
-15%
142%
-37%
-13% -3%
-18%
-7%
-12%
0%
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15%
8%
48%
-28%
-13%
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-50%
0%
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0
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350
400
450
500
Con
cen
trat
ion
s (µ
g/L
) Temporal distributions of Total Phosphorus at sites 10 through 18 (Group B sites)
Beaver Creek@New Hartford Beaver Creek@Cedar Falls Cedar River@Cedar Falls Cedar River@Waterloo
Black Hawk Creek@Waterloo Black Hawk Creek@Hudson Cedar River@Gilbertville Wolf Creek near Dysart
Cedar River near La Porte City %change
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Figure 9: Spatial variations in total phosphorus (TP) at sites 1 through 9 (Group A)
0
50
100
150
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250
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Cedar
River@CharlesCity
Little Cedar River
near Ionia
Shell Rock
River@MarbleRock
Shell Rock River
near Clarksville
Shell Rock@Shell
Rock
West Fork Cedar
River near Kesley
West Fork Cedar
River@Finchford
Cedar
River@Waverly
Cedar
River@Janesville
Con
cen
trato
ins
(µg
/L)
Spatial distributions of total phosphorus at sites 1 through 9 (group A sites)
4/5 4/19 4/25 5/3 5/10
5/17 5/26 6/1 6/8 6/15
6/21 6/28 7/5 7/12 7/19
7/26 8/2 8/9 8/17 8/23
8/29 9/5 9/12 9/19 9/26
10/3 10/10 10/15 10/25 10/31
Recommended Level
19
Figure 10: Spatial variations in total phosphorus (TP) at sites 10 through 18 (Group B)
0
50
100
150
200
250
300
350
400
450
Beaver
Creek@NewHartford
Beaver
Creek@Cedar Falls
Cedar River@Cedar
Falls
Cedar
River@Waterloo
Black Hawk
Creek@Waterloo
Black Hawk
Creek@Hudson
Cedar
River@Gilbertville
Wolf Creek near
Dysart
Cedar River near La
Porte City
Con
cen
trato
ins
(µg
/L)
Spatial distributions of total phosphorus at sites 10 through 18 (Group B sites)
4/5 4/19 4/25 5/3 5/105/17 5/26 6/1 6/8 6/156/21 6/28 7/5 7/12 7/197/26 8/2 8/9 8/17 8/238/29 9/5 9/12 9/19 9/2610/3 10/10 10/15 10/25 10/31Recommended Level
20
Figure 11: Average total phosphorus concentrations at all sites during phase 1 (April – October, 2014)
0
50
100
150
200
250
Ced
arR
iver
@C
har
les
Cit
y
Ced
ar R
iver
@W
aver
ly
Ced
arR
iver
@Ja
nes
vil
le
Ced
arR
iver
@C
edar
Fal
ls
Ced
arR
iver
@W
ater
loo
Ced
arR
iver
@G
ilber
tvil
le
Ced
arR
iver
nea
r L
a P
ort
e C
ity
Lit
tleC
edar
Riv
er n
ear
Ion
ia
Shel
lRo
ckR
iver
@M
arb
le R
ock
Shel
lRo
ck R
iver
nea
r C
lark
svil
le
Shel
lRo
ckR
iver
@S
hel
l R
ock
Wes
tFork
Ced
arR
iver
nea
r K
esle
y
Wes
tFork
Ced
arR
iver
@F
inch
ford
Bea
ver
Cre
ek@
New
Har
tfo
rd
Bea
ver
Cre
ek@
Ced
ar F
alls
Bla
ckH
awkC
reek
@W
ater
loo
Bla
ckH
awkC
reek
@H
udso
n
Wolf
Cre
ek n
ear
Dysa
rt
Main River Tributaries
Co
nce
ntr
atio
ns
(µg/L
) Average Total Phosphorus Concentrations
21
Figure 12: Three-week comparison of total phosphorus during Phase 1 study.
0 50 100 150 200 250 300 350 400 450
Cedar River@Charles City
Little Cedar River near Ionia
Shell Rock River@Marble Rock
Shell Rock River near Clarksville
Shell Rock@Shell Rock
West Fork Cedar River near Kesley
West Fork Cedar River@Finchford
Cedar River@Waverly
Cedar River@Janesville
Beaver Creek@New Hartford
Beaver Creek@Cedar Falls
Cedar River@Cedar Falls
Cedar River@Waterloo
Black Hawk Creek@Waterloo
Black Hawk Creek@Hudson
Cedar River@Gilbertville
Wolf Creek near Dysart
Cedar River near La Porte City
Concentrations (µgP/L)
Phosphorus Concentrations
[Jun15-28, 2014]
6/15 6/21 6/28 USEPA Recommended Level
22
Figure 13: Total Phosphorus loads (in tons/day) at selected sites from Group A
0.01
0.1
1
10
100
Cedar River @ Charles
City
Cedar River @ Waverly Cedar River @ Janesville Little Cedar River near
Ionia
Shell Rock River at Shell
Rock
West Fork Cedar River @
Finchford
Lo
ads
(to
ns/
day
) Total phosphorus (TP) Loads at selected sites from Group A
4/5 4/19 4/25 5/3 5/10 5/17 5/26 6/1 6/8 6/15 6/21 6/28 7/5 7/12 7/19
7/26 8/2 8/9 8/17 8/23 8/29 9/5 9/12 9/19 9/26 10/3 10/10 10/15 10/25 10/31
23
Figure 14: Total phosphorus loads (in tons/day) at selected sites from Group B
0.01
0.1
1
10
100
Cedar River @ Cedar Falls Cedar River @ Waterloo Beaver Creek @ New Hartford Black Hawk Creek @ Hudson Wolf Creek near Dysart
Lo
ads
(to
ns/
day
) Total phosphorus Loads at selected sites from Group B
4/5 4/19 4/25 5/3 5/10 5/17 5/26 6/1 6/8 6/15 6/21 6/28 7/5 7/12 7/19
7/26 8/2 8/9 8/17 8/23 8/29 9/5 9/12 9/19 9/26 10/3 10/10 10/15 10/25 10/31
24
Figure 15: Temporal distributions of NO3-N concentrations at sites 1 through 9 (Group A)
0%
64%
37%
96%
-28%
26%
-34%
-10%
54%
-30%
14%
21%
13%
-31%
-22%
-28%
-10%
-2%
-20%
-10%
-10%
107%
-12%
6%
-2%
-6%
9%
12%
11%
-22%
-60%
-40%
-20%
0%
20%
40%
60%
80%
100%
120%
0
5
10
15
20
25
% C
han
ge
Co
nce
ntr
atio
ns
(mg/L
)
Temporal distributions of NO3-N
[Group A sites]
Cedar River@Charles City Little Cedar River near Ionia Shell Rock River@Marble Rock
Shell Rock River near Clarksville Shell Rock@Shell Rock West Fork Cedar River near Kesley
West Fork Cedar River@Finchford Cedar River@Waverly Cedar River@Janesville
%Change
25
Figure 16: Temporal distributions of NO3-N concentrations at sites 10 through 18 (Group B)
0%
93%
-8%
103%
-25%
40%
-32%
-17%
27%
-23%
23%
14%
31%
-20%
-19%
-24%
-10%
-3%
-27%
-16%
-19%
92%
-6%
-6%
-9%
-7%
21%
11%
25%
-14%
-40%
-20%
0%
20%
40%
60%
80%
100%
120%
0
5
10
15
20
25
% C
han
ge
Co
nce
ntr
atio
ns
(mg/L
) Temporal distributions of NO3-N
[Group B sites]
Beaver Creek@New Hartford Beaver Creek@Cedar Falls Cedar River@Cedar Falls Cedar River@Waterloo
Black Hawk Creek@Waterloo Black Hawk Creek@Hudson Cedar River@Gilbertville Wolf Creek near Dysart
Cedar River near La Porte City %Change
26
Figure 17: Spatial variations in NO3-N concentrations at sites 1 through 9 (Group A)
0
5
10
15
20
25
Cedar
River@Charles
City
Little Cedar River
near Ionia
Shell Rock
River@Marble
Rock
Shell Rock River
near Clarksville
Shell
Rock@Shell
Rock
West Fork Cedar
River near Kesley
West Fork Cedar
River@Finchford
Cedar
River@Waverly
Cedar
River@Janesville
Con
cen
trati
on
s (m
g/L
) Spatial distributions of NO3-N (Group A sites)
4/5 4/19 4/25 5/3 5/10 5/17 5/26 6/1 6/8 6/15 6/21 6/28 7/5 7/12 7/19
7/26 8/2 8/9 8/17 8/23 8/29 9/5 9/12 9/19 9/26 10/3 10/10 10/15 10/25 10/31
27
Figure 18: Spatial variations in NO3-N concentrations at sites 10 through 18 (Group B)
0
5
10
15
20
25
Beaver
Creek@NewHartford
Beaver
Creek@Cedar Falls
Cedar
River@Cedar Falls
Cedar
River@Waterloo
Black Hawk
Creek@Waterloo
Black Hawk
Creek@Hudson
Cedar
River@Gilbertville
Wolf Creek near
Dysart
Cedar River near
La Porte City
Con
cen
trati
on
s (m
g/L
) Spatial distributions of NO3-N (Group B sites)
4/5 4/19 4/25 5/3 5/10 5/17 5/26 6/1 6/8 6/15 6/21 6/28 7/5 7/12 7/19
7/26 8/2 8/9 8/17 8/23 8/29 9/5 9/12 9/19 9/26 10/3 10/10 10/15 10/25 10/31
28
Figure 19: Average NO3-N concentrations at all sites during Phase 1 (April – October, 2014)
0
2
4
6
8
10
12
14
Ced
ar R
iver
@C
har
les
Cit
y
Ced
ar R
iver
@W
aver
ly
Ced
ar R
iver
@Ja
nes
vil
le
Ced
ar R
iver
@C
edar
Fal
ls
Ced
ar R
iver
@W
ater
loo
Ced
ar R
iver
@G
ilber
tvil
le
Ced
ar R
iver
nea
r L
a P
ort
e C
ity
Lit
tle
Ced
ar R
iver
nea
r Io
nia
Shel
l R
ock
Riv
er@
Mar
ble
Ro
ck
Shel
l R
ock
Riv
er n
ear
Cla
rksv
ille
Shel
l R
ock
@S
hel
l R
ock
Wes
t F
ork
Ced
ar R
iver
nea
r K
esle
y
Wes
t F
ork
Ced
ar R
iver
@F
inch
ford
Bea
ver
Cre
ek@
New
Har
tford
Bea
ver
Cre
ek@
Ced
ar F
alls
Bla
ck H
awk C
reek
@W
ater
loo
Bla
ck H
awk C
reek
@H
udso
n
Wolf
Cre
ek n
ear
Dysa
rt
Main River Tributaries
Con
cen
trat
ion
s (m
g/L
) Average NO3-N Concentrations
29
Figure 20: NO3-N loads (in tons/day) at sites 1 through 9 (Group A)
0.1
1
10
100
1000
Cedar River @ Charles City Cedar River @ Waverly Cedar River @ Janesville Little Cedar River near Ionia Shell Rock River @ Shell
Rock
West Fork Cedar River @
Finchford
Lo
ads
(to
ns/
day
) NO3-N Loads at sites 1 through 9 (Group A sites)
4/5 4/19 4/25 5/3 5/10 5/17 5/26 6/1 6/8 6/15 6/21 6/28 7/5 7/12 7/19
7/26 8/2 8/9 8/17 8/23 8/29 9/5 9/12 9/19 9/26 10/3 10/10 10/15 10/25 10/31
30
Figure 21: NO3-N loads (in tons/day) at sites 10 through 18 (Group B)
0.1
1
10
100
1000
10000
Cedar River @ Cedar Falls Cedar River @ Waterloo Beaver Creek @ New Hartford Black Hawk Creek @ Hudson Wolf Creek near Dysart
Lo
ads
(to
ns/
day
) NO3-N Loads at sites 10 through 18 (Group B sites)
4/5 4/19 4/25 5/3 5/10 5/17 5/26 6/1 6/8 6/15 6/21 6/28 7/5 7/12 7/19
7/26 8/2 8/9 8/17 8/23 8/29 9/5 9/12 9/19 9/26 10/3 10/10 10/15 10/25 10/31
31
Figure 22: Seasonal distributions of NO3-N (Phase 1)
32
Figure 23: Average NO3-N load distributions at 11 sites where discharge data are available (see report)
33
Figure 24: Seasonal distributions of total phosphorus (TP)
34
Figure 25: Average TP load distributions at 11 sites where discharge data are available (see report)
35
Figure 26: Temporal variations in TP as compared to rainfall [Weather Station: Charles City (Floyd)]
0
5
10
15
20
25
0
50
100
150
200
250
300
350
400
450
5004
/5
4/1
9
4/2
5
5/3
5/1
0
5/1
7
5/2
6
6/1
6/8
6/1
5
6/2
1
6/2
8
7/5
7/1
2
7/1
9
7/2
6
8/2
8/9
8/1
7
8/2
3
8/2
9
9/5
9/1
2
9/1
9
9/2
6
10
/3
10
/10
10
/15
10
/25
10
/31
Pre
cip
itat
ion
(m
m)
Co
nce
ntr
atio
n (
µg/
L)
Precipitation Vs Total Phosphorus Concentration
CedarRiver @ CharlesCity LittleCedarRiver near Ionia ShellRockRiver @ MarbleRock Precipitation
36
Figure 27: Temporal variations in TP as compared to rainfall [Weather Station: Alison (Butler)]
0
2
4
6
8
10
12
14
16
18
0
50
100
150
200
250
300
350
400
4/5
4/1
9
4/2
5
5/3
5/1
0
5/1
7
5/2
6
6/1
6/8
6/1
5
6/2
1
6/2
8
7/5
7/1
2
7/1
9
7/2
6
8/2
8/9
8/1
7
8/2
3
8/2
9
9/5
9/1
2
9/1
9
9/2
6
10
/3
10
/10
10
/15
10
/25
10
/31
Pre
cip
itat
ion
(m
m)
Co
nce
ntr
atio
n (
µg/
L)
Precipitation Vs Total Phosphorus Concentration
ShellRockRiver @ Clarksville ShellRockRiver @ ShellRock WestForkCedarRiver near Kesley
CedarRiver @ Waverly Precipitation
37
Figure 28: Temporal variations in TP as compared to rainfall [Weather Station: Waterloo Municipal Airport (Black Hawk)]
0
2
4
6
8
10
12
14
16
18
0
50
100
150
200
250
300
350
400
4/5
4/1
9
4/2
5
5/3
5/1
0
5/1
7
5/2
6
6/1
6/8
6/1
5
6/2
1
6/2
8
7/5
7/1
2
7/1
9
7/2
6
8/2
8/9
8/1
7
8/2
3
8/2
9
9/5
9/1
2
9/1
9
9/2
6
10
/3
10
/10
10
/15
10
/25
10
/31
Pre
cip
itat
ion
(m
m)
Co
nce
ntr
atio
n (
µg/
L)
Precipitation Vs Total Phosphorus Concentration [Main Channel]
CedarRiver @ Janesville CedarRiver @ CedarFalls CedarRiver @ WaterlooCedarRiver @ Gilbertville CedarRiver @ LaPorteCity Precipitation
38
Figure 29: Temporal variations in TP as compared to rainfall [Weather Station: Waterloo Municipal Airport (Black Hawk)]
0
2
4
6
8
10
12
14
16
18
0
50
100
150
200
250
300
350
400
450
4/5
4/1
9
4/2
5
5/3
5/1
0
5/1
7
5/2
6
6/1
6/8
6/1
5
6/2
1
6/2
8
7/5
7/1
2
7/1
9
7/2
6
8/2
8/9
8/1
7
8/2
3
8/2
9
9/5
9/1
2
9/1
9
9/2
6
10
/3
10
/10
10
/15
10
/25
10
/31
Pre
cip
itat
ion
(m
m)
Co
nce
ntr
atio
n (
µg/
L)
Precipitation Vs Total Phosphorus Concentration [Tributaries]
WestForkCedarRiver @ Finchford BeaverCreek @ NewHartford BeaverCreek @ CedarFalls
BlackHawkCreek @ Waterloo BlackHawkCreek @ Hudson Precipitation
39
Figure 30: Relationships between total suspended solids and total phosphorus (Sites 1 – 18)
0
20
40
60
80
100
120
140
0
50
100
150
200
250
300
350
4/5
4/1
9
4/2
5
5/3
5/1
0
5/1
7
5/2
6
6/1
6/8
6/1
5
6/2
1
6/2
8
7/5
7/1
2
7/1
9
7/2
6
8/2
8/9
8/1
7
8/2
3
8/2
9
9/5
9/1
2
9/1
9
9/2
6
10
/3
10
/10
10
/15
10
/25
10
/31
Sampling dates
Ave
rage
TSS
Co
nce
ntr
atio
n (
mg/
L)
Ave
rage
TP
Co
nce
ntr
atio
n (
µg/
L)
Relationship between TSS and TP
40
Figure 31: Average T concentrations at sites 1 – 18 (Phase 1)
41
Figure 32: Average NO3 - N concentrations at sites 1 – 18 (Phase 1)
42
Figure 33: Average TSS concentrations at sites 1 – 18 (Phase 1)
43
Figure 34: NO3 – N load calculations at 11 selected sites (shown from upstream to downstream locations)
Site_ID Name of sites
Monthly Average NO3-N Loads (tons/day) Average
Load (tons/day)
Total Load (for 7
months)
Subwatershed_Area (acre)
Total Loads [tons/acre]
(for 7 months)
Total Loads [pounds/acre]
(Apr-Oct) April May June July August September October
S1 Cedar River @ Charles City 29.42 77.94 103.54 21.97 3.73 8.36 9.43 36.343 7631.986 686563.5123 1.E-02 22.23
S2 Little Cedar River 12.64 23.11 29.33 8.42 0.55 2.55 3.78 11.485 2411.752 189413.6103 1.E-02 25.47
S5 Shell Rock River 20.07 90.30 114.19 45.45 4.37 10.03 8.42 41.833 8784.963 1091331.079 8.E-03 16.10
S8 Cedar River @ Waverly 32.23 132.96 167.51 52.09 5.25 11.70 11.52 59.037 12397.731 996235.3056 1.E-02 24.89
S7 West Fork Cedar River 18.36 81.04 72.59 75.08 6.31 10.18 8.88 38.919 8172.921 542370.3165 2.E-02 30.14
S9 Cedar River @ Janesville 38.65 142.87 171.19 59.72 5.58 11.92 13.34 63.325 13298.158 1067863.985 1.E-02 24.91
S10 Beaver Creek 4.28 18.26 34.88 25.78 1.57 1.40 3.80 12.852 2698.919 251845.5994 1.E-02 21.43
S12 Cedar River @ Cedar Falls 20.43 93.29 98.32 64.34 18.73 35.76 36.18 52.437 11011.704 3007499.163 4.E-03 7.32
S15 Black Hawk Creek 3.78 7.74 35.03 17.36 1.18 0.47 1.23 9.544 2004.138 209267.6794 1.E-02 19.15
S13 Cedar River @ Waterloo 77.44 334.64 376.52 222.71 28.56 26.51 29.82 156.602 32886.370 3260286.826 1.E-02 20.17
S17 Wolf Creek 2.88 6.64 19.40 21.54 2.21 2.27 3.69 8.377 1759.240 190907.6582 9.E-03 18.43
44
Figure 35: TP load calculations at 11 selected sites (shown from upstream to downstream locations)
Site_ID Subwatersheds
Monthly Average Phosphorus Loads (tons/day) Average
Load (tons/day)
Total Load (for 7
months)
Subwatershed_Area (acre)
Total Loads [tons/acre]
(for 7 months)
Total Loads [pounds/acre]
(Apr-Oct) April May June July August September October
S1 Cedar River @ Charles City 0.875 0.665 2.057 0.251 0.122 0.188 0.138 0.614 128.861 686563.5123 2.E-04 0.375
S2 Little Cedar River 0.522 0.183 0.480 0.076 0.018 0.066 0.040 0.198 41.527 189413.6103 2.E-04 0.438
S5 Shell Rock River 0.917 1.066 3.150 1.102 0.199 0.451 0.142 1.004 210.803 1091331.079 2.E-04 0.386
S8 Cedar River @ Waverly 1.322 1.392 3.780 0.635 0.168 0.369 0.154 1.117 234.643 996235.3056 2.E-04 0.471
S7 West Fork Cedar River 0.444 0.734 1.820 0.966 0.098 0.183 0.077 0.617 129.618 542370.3165 2.E-04 0.478
S9 Cedar River @ Janesville 1.685 1.607 3.561 0.711 0.170 0.402 0.188 1.189 249.722 1067863.985 2.E-04 0.468
S10 Beaver Creek 0.084 0.160 1.246 0.304 0.032 0.032 0.055 0.273 57.393 251845.5994 2.E-04 0.456
S12 Cedar River @ Cedar Falls 2.753 4.292 9.233 3.431 0.486 1.204 0.472 3.124 656.135 3007499.163 2.E-04 0.436
S15 Black Hawk Creek 0.075 0.068 1.267 0.173 0.026 0.018 0.027 0.236 49.653 209267.6794 2.E-04 0.475
S13 Cedar River @ Waterloo 3.210 4.143 7.978 3.683 0.571 1.448 0.614 3.092 649.393 3260286.826 2.E-04 0.398
S17 Wolf Creek 0.062 0.065 0.382 0.230 0.039 0.049 0.060 0.127 26.619 190907.6582 1.E-04 0.279
45
Figure 36: TSS load calculations at 11 selected sites (shown from upstream to downstream locations)
Site_ID Name of sites
Monthly Average TSS Loads (tons/day)
Average Load (tons/day)
Total Load (for 7
months)
Subwatershed_Area (acre)
Total Loads [tons/acre]
(for 7 months)
Total Loads [pounds/acre]
(Apr-Oct) April May June July August September October
S1 Cedar River @ Charles City 38.05 16.36 42.21 16.20 21.20 7.80 3.42 20.748 4357.113 686563.5123 6.E-03 12.69
S2 Little Cedar River 156.07 48.90 52.56 26.43 17.80 24.75 10.12 48.091 10099.158 189413.6103 5.E-02 106.64
S5 Shell Rock River 47.64 28.69 37.21 25.98 22.70 14.47 5.02 25.957 5451.064 1091331.079 5.E-03 9.99
S8 Cedar River @ Waverly 42.51 36.15 56.19 32.85 19.43 14.93 6.68 29.819 6261.981 996235.3056 6.E-03 12.57
S7 West Fork Cedar River 64.02 39.69 44.01 44.43 25.83 30.09 14.92 37.570 7889.651 542370.3165 1.E-02 29.09
S9 Cedar River @ Janesville 35.97 41.52 55.73 33.17 31.38 17.08 3.58 31.205 6552.973 1067863.985 6.E-03 12.27
S10 Beaver Creek 28.12 54.20 60.06 45.34 21.81 15.69 14.33 34.221 7186.390 251845.5994 3.E-02 57.07
S12 Cedar River @ Cedar Falls 39.21 32.44 65.03 33.83 24.56 11.45 5.94 30.349 6373.332 3007499.163 2.E-03 4.24
S15 Black Hawk Creek 24.18 19.14 86.31 44.64 12.17 8.20 10.63 29.324 6158.088 209267.6794 3.E-02 58.85
S13 Cedar River @ Waterloo 31.66 28.43 38.17 29.18 22.16 15.05 7.72 24.623 5170.738 3260286.826 2.E-03 3.17
S17 Wolf Creek 29.49 43.61 239.40 83.60 14.46 24.20 34.20 66.995 14069.037 190907.6582 7.E-02 147.39
46
Figure 37: NO3 – N, TP and TSS load comparison in 11 selected sites (shown from upstream to downstream loactions)
Site_ID Name of sites Total NO3-N Loads
[pounds/acre] (Apr-Oct) Total TP Loads
[pounds/acre] (Apr-Oct) Total TSS Loads
[pounds/acre] (Apr-Oct)
S1 Cedar River @ Charles City 22.23 0.375 12.69
S2 Little Cedar River 25.47 0.438 106.64
S5 Shell Rock River 16.10 0.386 9.99
S8 Cedar River @ Waverly 24.89 0.471 12.57
S7 West Fork Cedar River 30.14 0.478 29.09
S9 Cedar River @ Janesville 24.91 0.468 12.27
S10 Beaver Creek 21.43 0.456 57.07
S12 Cedar River @ Cedar Falls 7.32 0.436 4.24
S15 Black Hawk Creek 19.15 0.475 58.85
S13 Cedar River @ Waterloo 20.17 0.398 3.17
S17 Wolf Creek 18.43 0.279 147.39
47
Figure 38: Phase 1 study area with delineated sub-watersheds
48
Figure 39: NO3 – N loads per acre and percent row crops shown for each sub-watershed (Phase 1)
49
Figure 40: Total NO3 – N loads for the year and percent row crops shown for each sub-watershed (Phase 1)
50
Figure 41: TP loads per acre and percent row crops shown for each sub-watershed (Phase 1)
51
Figure 42: Total TP loads for the year and percent row crops shown for each sub-watershed (Phase 1)
52
Figure 43: Temporal distributions of TP in stream sediments at 9 selected sites from Group A
0%
-48%
-14%
-60%
100%
-45%
35%
-26%
17%
-6%
-80%
-60%
-40%
-20%
0%
20%
40%
60%
80%
100%
120%
0
100
200
300
400
500
600
700
800
4/5 4/19 5/10 6/1 7/19 8/9 8/29 9/19 10/10 10/31
Con
cen
trat
ion
s (µ
gP
/gd
w)
Temporal Distributions of Total Phosphorus in Sediments
Cedar River@Charles City Little Cedar River near Ionia Shell Rock River@Marble RockShell Rock River near Clarksville Shell Rock@Shell Rock West Fork Cedar River near KesleyWest Fork Cedar River@Finchford Cedar River@Waverly Cedar River@Janesville%change
53
Figure 44: Temporal distributions of TP in stream sediments at 8 selected sites from Group B
0%
-37% -55%
-15%
0%
64%
36%
-17%
48%
-58%
-80%
-60%
-40%
-20%
0%
20%
40%
60%
80%
0
100
200
300
400
500
600
700
800
4/5 4/19 5/10 6/1 7/19 8/9 8/29 9/19 10/10 10/31
Con
cen
trat
ion
s (µ
gP
/gd
w)
Temporal Distributions of Total Phosphorus in Sediments
Beaver Creek@New Hartford Beaver Creek@Cedar Falls Cedar River@Cedar Falls
Black Hawk Creek@Waterloo Black Hawk Creek@Hudson Cedar River@Gilbertville
Wolf Creek near Dysart Cedar River near La Porte City %change
54
Figure 45: Spatial distributions of TP in stream sediments at 9 selected sites from Group A
0
100
200
300
400
500
600
700
800
Cedar
River@CharlesCity
Little Cedar River
near Ionia
Shell Rock
River@MarbleRock
Shell Rock River
near Clarksville
Shell Rock@Shell
Rock
West Fork Cedar
River near Kesley
West Fork Cedar
River@Finchford
Cedar
River@Waverly
Cedar
River@Janesville
Con
cen
trato
ins
(µg
P/g
dw
)
Spatial distributions of Total Phosphorus in sediments
4/5 4/19 5/10 6/1 7/19 8/9 8/29 9/19 10/10 10/31
55
Figure 46: Spatial distributions of TP in stream sediments at 8 selected sites from Group B
0
100
200
300
400
500
600
700
800
Beaver
Creek@NewHartford
Beaver
Creek@Cedar Falls
Cedar
River@Cedar Falls
Black Hawk
Creek@Waterloo
Black Hawk
Creek@Hudson
Cedar
River@Gilbertville
Wolf Creek near
Dysart
Cedar River near
La Porte City
Con
cen
trato
ins
(µg
P/g
dw
) Spatial distributions of Total Phosphorus in sediments
4/5 4/19 5/10 6/1 7/19 8/9 8/29 9/19 10/10 10/31
56
Figure 47: Relationships of dissolved P and adsorbed P with TSS
R² = 0.1189
R² = 0.0004
0
100
200
300
400
500
600
700
800
0
100
200
300
400
500
0 100 200 300 400 500 600
TP
sed
imen
ts
TP
wat
er
TSS
Relationship of TPwater and TPsediment with TSS
TPwater
TPsediments
57
Figure 48: Map showing 10 sites from Phase 2 of the study (sites 19 – 28)
58
Figure 49: Temporal distributions of TSS (Phase 2)
27.48
41.68 46.03
17.12
110.01
192.17
54.45
41.98
50.78
45.55
42.77 50.67
39.49
13.94
26.85
16.04
0
50
100
150
200
250
0
1
10
100
1000
4-Apr 18-Apr 2-May 15-May 30-May 13-Jun 28-Jun 11-Jul 26-Jul 8-Aug 21-Aug 4-Sep 18-Sep 8-Oct 23-Oct 30-Oct
Aver
age
Con
cen
trat
ion
(m
g/L
)
Log C
on
cen
trat
ion
(m
g/L
) Temporal Distributions of TSS
Cedar River near Brandon Cedar River @ Vinton Cedar River near Urbana Cedar River @ Palo
Indian Creek @ Marion Cedar River @ Cedar Rapids Average
59
Figure 50: Spatial distributions of TSS (Phase 2)
1
10
100
1000
Cedar River near Brandon Cedar River @ Vinton Cedar River near Urbana Cedar River @ Palo Indian Creek @ Marion Cedar River @ Cedar
Rapids
Log C
on
cen
trat
ion
(m
g/L
)
TSS Distributions at Selected Sites
of the Study Area
4-Apr 18-Apr 2-May 15-May 30-May 13-Jun 28-Jun 11-Jul 26-Jul 8-Aug 21-Aug 4-Sep 18-Sep 8-Oct 23-Oct 30-Oct
60
ID Name of sites
Monthly Average TSS Loads (tons/day)
Average Load
(tons/day)
Total Load (for 7
months)
Subwatershed_Area (acre)
Total Loads [tons/acre] (for
7 months)
Total Loads [pounds/acre]
(Apr-Oct) April May June July Aug Sep Oct
S20 Cedar River at Vinton 769.55 580.49 3498.83 585.58 375.20 724.25 110.67 949.224 199336.973 3823736.241 5.E-02 104.26
S22 Cedar River at Palo 760.85 3804.01 3222.36 758.09 716.78 758.09 156.11 1453.755 305288.535 4019579.024 8.E-02 151.90
S23 Indian Creek at Marion 0.13 0.46 162.50 1.57 0.55 11.67 0.42 25.330 5319.304 43572.91438 1.E-01 244.16
S24 Cedar River at Cedar Rapids 361.48 534.07 9758.98 401.85 236.39 530.18 193.00 1716.565 360478.630 4126629.079 9.E-02 174.71
Figure 51: Load calculations of TSS at sites 20, 22, 23 and 24
61
Figure 52: Temporal distributions of total phosphorus at selected sites (Phase 2)
0% 31%
-45%
37%
-1%
89%
-21%
-55%
58%
-19%
129%
-40%
1%
-31%
-46%
53%
-100%
-50%
0%
50%
100%
150%
0
50
100
150
200
250
300
350
400
450
4-Apr 18-Apr 2-May 15-May 30-May 13-Jun 28-Jun 11-Jul 26-Jul 8-Aug 21-Aug 4-Sep 18-Sep 8-Oct 23-Oct 30-Oct
Con
cen
trat
ion
s (µ
g/L
)
Temporal Distributions of Total Phosphorus
Cedar River near Brandon Cedar River @ Vinton Cedar River near Urbana Cedar River @ Palo
Indian Creek @ Marion Cedar River @ Cedar Rapids %change
62
Figure 53: Spatial distributions of total phosphorus at selected sites (Phase 2)
0
50
100
150
200
250
300
350
400
450
Cedar River near Brandon Cedar River @ Vinton Cedar River near Urbana Cedar River @ Palo Indian Creek @ Marion Cedar River @ Cedar
Rapids
Con
cen
trato
ins
(µg
/L)
Total Phosphorus Distributions at Six Sites
of the Study Area
4-Apr 18-Apr 2-May 15-May 30-May
13-Jun 28-Jun 11-Jul 26-Jul 8-Aug
21-Aug 4-Sep 18-Sep 8-Oct 23-Oct
30-Oct Recommended Level
63
ID Name of sites
Monthly Average Phosphorus Loads (tons/day)
Average Load
(tons/day)
Total Load (for 7
months)
Subwatershed_Area (acre)
Total Loads [tons/acre] (for
7months)
Total Loads [pounds/acre]
(Apr-Oct) April May June July Aug Sep Oct
S20 Cedar River at Vinton 3.86 2.45 8.51 1.25 1.63 1.54 0.70 2.849 598.312 3823736.241 2.E-04 0.31
S22 Cedar River at Palo 2.61 2.89 14.34 1.72 2.33 2.67 0.71 3.897 818.321 4019579.024 2.E-04 0.41
S23 Indian Creek at Marion 0.00 0.01 0.36 0.02 0.01 0.03 0.01 0.062 13.001 43572.91438 3.E-04 0.60
S24 Cedar River at Cedar Rapids 2.67 2.42 13.73 1.26 1.93 2.80 0.70 3.644 765.264 4126629.079 2.E-04 0.37
Figure 54: Load calculations of TP at sites 20, 22, 23 and 24
64
Figure 55: Temporal distributions of NO3-N at selected sites (Phase 2)
0%
183%
-12% -3%
77%
7%
-79%
246%
-29% -45% -44%
141%
-23%
17%
-39%
74%
-100%
-50%
0%
50%
100%
150%
200%
250%
300%
0
5
10
15
20
25
4-Apr 18-Apr 2-May 15-May 30-May 13-Jun 28-Jun 11-Jul 26-Jul 8-Aug 21-Aug 4-Sep 18-Sep 8-Oct 23-Oct 30-Oct
Per
cent
chan
ge
(%)
Co
nce
ntr
atio
ns
(mg/L
)
Temporal distributions of NO3-N concentrations
Cedar River near Brandon Cedar River @ Vinton Cedar River near Urbana
Cedar River @ Palo Indian Creek @ Marion Cedar River @ Cedar Rapids
%Change
65
Figure 56: Spatial distributions of NO3-N at selected sites (Phase 2)
0
5
10
15
20
25
Cedar River near
Brandon
Cedar River @ Vinton Cedar River near
Urbana
Cedar River @ Palo Indian Creek @
Marion
Cedar River @ Cedar
Rapids
Con
cen
trati
on
s (m
g/L
) NO3-N concentrations at six sites of the study area
4-Apr 18-Apr 2-May 15-May 30-May 13-Jun 28-Jun 11-Jul
26-Jul 8-Aug 21-Aug 4-Sep 18-Sep 8-Oct 23-Oct 30-Oct
66
Figure 57: Load calculations of NO3-N at sites 20, 22, 23 and 24
ID Name of sites
Monthly Average NO3-N Loads (tons/day) Average
Load (tons/day)
Total Load (for 7
months)
Subwatershed_Area (acre)
Total Loads [tons/acre] (for
7months)
Total Loads [pounds/acre]
(Apr-Oct)
April May June July Aug Sep Oct
S20 Cedar River at Vinton 142.47 194.68 234.23 137.83 38.28 81.84 36.25 123.655 25967.447 3823736.241 7.E-03 13.58
S22 Cedar River at Palo 127.42 216.01 313.88 126.08 42.80 101.16 40.39 138.247 29031.867 4019579.024 7.E-03 14.45
S23 Indian Creek at Marion 0.21 1.69 19.48 1.26 0.05 0.11 0.46 3.321 697.380 43572.91438 2.E-02 32.01
S24 Cedar River at Cedar Rapids 128.94 229.23 404.73 129.77 39.95 96.71 40.58 152.842 32096.881 4126629.079 8.E-03 15.56
67
Figure 58: Loads comparison of NO3-N, TP and TSS at sites 20, 22, 23 and 24 (Phase 2)
ID Name of sites Sub-watershed Area
(acre)
Total NO3-N Loads
[pounds/acre] (Apr-Oct)
Total TP Loads [pounds/acre]
(Apr-Oct)
Total TSS Loads [pounds/acre]
(Apr-Oct)
S20 Cedar River at Vinton 3823736.241 13.58 0.31 104.26
S22 Cedar River at Palo 4019579.024 14.45 0.41 151.90
S23 Indian Creek at Marion 43572.91438 32.01 0.60 244.16
S24 Cedar River at Cedar Rapids 4126629.079 15.56 0.37 174.71
68
Figure 59: Relationships between TSS and TP (Phase 2)
y = 0.4784x + 149.78 R² = 0.1474
0
50
100
150
200
250
300
350
400
450
0 50 100 150 200 250 300 350 400 450 500
TSS
(mg/
L)
Total phosphorus (µg/L)
Relationship between TSS and TP
69
Figure 60: Relationships of dissolved TP and sediment-adsorbed TP with TSS (Phase 2)
R² = 0.1474
R² = 0.0015
0
100
200
300
400
500
600
700
800
900
0
50
100
150
200
250
300
350
400
450
0 50 100 150 200 250 300 350 400 450
TSS
TPse
dim
ents
TPw
ater
Relationship of TPwater and TPsediment with TSS
TPwater
TPsediments
70
Figure 61: Spatial distributions of phosphorus in stream sediments at sites 19 – 24
0
200
400
600
800
1000
S19 S20 S21 S22 S23 S24
mg/
kg (
dry
wt)
Sites
Spatial distributions of total phosphorus in sediments
2-May 13-Jun 11-Jul 21-Aug 18-Sep
71
Fig. 62: Data recorded at sites 25, 26, 27 and 28 during early, middle and late seasons of 2015 (Phase 2)
Site_ID Date pH Temp DO Conductivity TDS Turbidity TSS Chloride Sulfate NO3-N T. Phosphorus
Site 25 4.4.15 9.09 14.00 11.50 618 420 17.00 50.89 43.61 44.28 3.90 290.0
Site 26 4.4.15 7.98 11.20 14.86 585 411 2.70 0.50 17.16 13.62 5.34 120.0
Site 27 4.4.15 9.15 14.00 15.29 611 420 12.80 60.30 40.68 43.82 3.47 230.0
Site 28 4.4.15 8.88 14.30 11.08 597 405 26.70 71.05 27.20 38.29 3.14 180.0
Site 25 8.8.15 8.86 25.60 9.26 591 407 32.80 51.20 27.95 34.91 6.08 260.0
Site 26 8.8.15 8.29 21.80 8.52 631 437 14.60 18.90 20.37 26.07 5.33 180.0
Site 27 8.8.15 8.88 26.50 9.96 558 385 46.20 62.00 25.22 32.25 5.83 190.0
Site 28 8.8.15 8.81 26.40 8.11 528 381 41.20 95.20 24.04 31.50 6.02 200.0
Site 25 10.30.15 9.28 10.60 11.70 594 408 25.80 47.78 35.62 36.79 5.89 120.0
Site 26 10.30.15 7.92 13.30 8.43 636 441 4.85 4.00 16.99 17.67 6.21 160.0
Site 27 10.30.15 9.35 11.30 11.92 524 362 46.00 73.50 31.54 36.21 4.20 60.0
Site 28 10.30.15 9.33 10.70 10.98 520 354 54.20 121.37 33.85 35.45 3.42 60.0