final project report submitted to iowa nutrient research ... · distribution, transport, and...

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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.

mailto:[email protected]

http://www.uni.edu/hydrology

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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

180

200

1

10

100

1000

Aver

age

Con

cen

trat

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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

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@C

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Cit

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Ced

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@W

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Lit

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Bea

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Bea

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Cre

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Bla

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Bla

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Wolf

Cre

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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%

21%

-2%

-11%

-60%

-40%

-20%

0%

20%

40%

60%

80%

100%

120%

140%

160%

0

50

100

150

200

250

300

350

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%

9%

15%

8%

48%

-28%

-13%

3%

-40%

4%

28%

9%

-22%

-50%

0%

50%

100%

150%

200%

0

50

100

150

200

250

300

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

200

250

300

350

400

450

500

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


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


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)



(for 7 months)









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




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)



(for 7 months)









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




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


60

ID Name of sites

Monthly Average TSS Loads (tons/day)

Average Load

(tons/day)

Total Load (for 7

months)


Total Loads [tons/acre] (for

7 months)


(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


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)



7months)


(Apr-Oct) April May June July Aug Sep Oct





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


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)



7months)


(Apr-Oct)

April May June July Aug Sep Oct





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

final project report submitted to iowa nutrient research ... · distribution, transport, and...

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