Nutrient Trends
in the Des Moines River
Donna S. Lutz
Des Moines River Water Quality Network
What is the Des Moines River
Water Quality Network?
• Initiated in July 1967 as preimpoundment study for
Saylorville Reservoir, expanded to Red Rock Reservoir in 1971
•Long-term record, 36 years at many sites, total of 182
parameters, nearly 445,000 individual data records
• Currently 7 regular sampling sites, monitored 22 times per
year for up to 50 parameters
•Data available through annual reports, paradox database,
webpage (soon to be on Iowa STORET)
Des Moines River Basin
•Length 350 mi
•Width 50 mi
•Basin 12,884 sq mi
about ¼ size of Iowa
Saylorville Reservoir
•24 mi valley/54 mi flood
•5,520 acres/ 16,100 flood
•1,100 ac-ft/yr
sedimentation
Red Rock Reservoir
•18 mi valley/33 mi flood
•15,250 acres/ 1,625,00 fl
•4,470 ac-ft/yr
sedimentation
Raccoon River Sub-basin
North Raccoon/Middle Raccoon/South Raccoon
Basin 3,411 sq mi
Routine Parameters

Physical



Chemical



temperature, flow/elevation
turbidity, secchi disc depth, gas saturation
dissolved oxygen, BOD, TOC, nutrients, suspended
solids
metals, pesticides
Biological


chlorophyll pigments
bacteria
Important Programs

Short term

bacteria at beaches




safe for fish?
overall monitoring


why? what’s up?
historical record


safe to eat?
total gas saturation

Long term
safe to swim?
pesticides in fish


trend analysis




any improvement?
suspended solids
nutrient


what is normal?
ammonia, nitrate, phosphate
pesticides
chlorophyll pigments
Significant Findings

Non-point sources are the main contaminants;


Point source loading has decreased



soil erosion and siltation primary resource problem
 Ave. loading to Red Rock 5,400 metric tons/day
Improved wastewater treatment has significantly reduced
ammonia loading
Nitrate levels increased until 1982, no current trend
Total Phosphate levels have decreased slightly, but
only by about 0.01 mg/year
Significant Findings (cont’d)



Overall, water quality has significantly improved at
most sites, according to water quality index values
Pesticide levels in fish are low, but may still be of concern
Gas supersaturation-induced gas bubble trauma
causes periodic fish kills below Red Rock Dam
Nutrient Trends

Total Nitrogen
Nitrogen Forms
 Nitrate
 Ammonia
 Nutrient criteria – total nitrogen (rivers)


Total Phosphorus
Orthophosphate
 Nutrient criteria – total phosphorus (rivers)
 Phosphorus in sediment

Importance of River Flow

Low Flow
Nutrients can decrease due to algal utilization
 However, nutrients may increase if there are point
sources due to lack of dilution


High Flow
Nutrients, especially nitrate and total phosphate may
increase with storm events
 Antecedent precipitation important

Algal Utilization
of nutrients under low flow
Temp
C
Flow
cfs
7/22/
2003
22.9
3240
8/5/
2003
24.4
856
Chl a
mg/m3
NH4
mg/l
NO3
mg/l
T PO4
mg/l
O PO4
mg/l
73
0.03
11.0
0.64
0.25
162
0.01
3.52
0.55
<0.03
Nitrogen Inputs
Dry Deposition
7%
Human
<1%
Industry
<1%
Manure
13%
Soil N
26%
Fertilizer
25%
Legumes
20%
Wet Deposition
9%
Estimated Point and Non-Point Source
Contributions to Stream N-Load
Point Source
8%
Non-Point
Source
92%
Nitrogen Forms, %
Above Saylorville Reservoir (St. 1)
Total N
Organic N
Ammonia N
NO2+NO3 N
1967-76 1977-81
100
100
2000-03
100
14
16
21
7
4
1
79
80
78
Below Saylorville Reservoir (St.5)
Total N
Organic N
Ammonia N
NO2+NO3 N
1967-76 1977-81
100
100
2000-03
100
16
15
13
6
7
2
78
78
85
Nitrogen Forms
Raccoon River near Van Meter
Total N monthly mean
1972-81 7.45 mg/l
2000-03 8.55 mg/l
15%
12%
1%
4%
84%
1972-81
84%
2000-03
Organic N
Ammonia N
NO2+NO3 N
10
1967-76
1977-81
2000-03
8
Nitrogen Forms, Concentration
Above Saylorville Reservoir (St. 1)
6
1967-76 1977-81
5.86
8.25
2000-03
7.89
4
Total N
2
Organic N
0.84
1.30
1.63
0
Ammonia N
0.40
0.30
0.06
NO3
NO2+NO3 N
4.62
6.65
6.20
2000-03
Below Saylorville Reservoir (St.5)
Tot N Org N Amm
10
1967-76
1977-81
8
6
1967-76 1977-81
5.67
6.55
2000-03
7.25
4
Total N
2
Organic N
0.89
0.99
0.97
0
Ammonia N
0.32
0.43
0.15
NO2+NO3 N
4.46
5.13
6.13
Tot N Org N
Amm
NO3
Nitrite +Nitrate N

Ammonia oxidized to nitrate (bacterially mediated)


Sources


Fertilizers, oxidation or organic N, fixation of N2,
precipitation, sewage effluents
Losses


Nitrite, intermediate product, (1967-76, max 0.68 mg/l, 99%
of samples <0.20 mg/l)
Leaching, assimilation living organisms, conversion to other
forms
Soluble, easily leaches from soil
Nitrate vs Flow Des Moines River near Boone
Nitrate
12
12000
10
10000
8
8000
6
6000
4
4000
2
2000
0
0
Flow (cfs)
Nitrate mg/l
Flow
2002
2000
1998
1996
1994
1992
1990
1988
1986
1984
1982
1980
1978
1976
1974
1972
1970
1968
Nitrate vs Flow Raccoon River near Van Meter
Nitrate
12
12000
10
10000
8
8000
6
6000
4
4000
2
2000
0
0
Flow (cfs)
Nitrate mg/l
Flow
2003
2001
1999
1997
1995
1993
1991
1989
1987
1985
1983
1981
1979
1977
1975
1973
Nitrate vs Flow
Des Moines River near Boone
R2 = 0.63
10
9
Nitrate (mg/l)
8
7
6
5
4
3
2
1
0
0
2000
4000
6000
Flow (cfs)
8000
10000
12000
Seasonality of Nitrate Concentrations
Raccoon River, monthly means unadjusted
Winter
Spring
Summer
Fall
Seasonality of Nitrate Concentrations
Raccoon River, monthly means flow adjusted
Winter
Spring
Summer
Fall
Seasonal Kendall Tau Trend Analysis, Significant
Trends (95%)
(from Monthly Mean Data, flow-adjusted)
NO2+NO3 N
NO2+NO3 N
n
mean
slope
Des Moines River near Boone
1967-2003
1967-1982
1983-2003
438
186
252
5.70
5.27
6.00
no trend
+ 0.23
no trend
NO2+NO3 N
n
mean
slope
Raccoon River near Van Meter
1972-2003
1972-1982
1982-2000
377
125
252
7.00
6.55
7.22
no trend
+ 0.36
no trend
Exceedance vs Flow
Des Moines River near Boone
Flow
Linear (months)
9
12000
8
10000
7
6
8000
5
6000
4
3
4000
2
2000
1
0
0
Flow (cfs)
# of months >10 mg/l Nitrate
months
2002
2000
1998
1996
1994
1992
1990
1988
1986
1984
1982
1980
1978
1976
1974
1972
1970
1968
Exceedance vs Flow
Raccoon River near Van Meter
months
Flow
Linear (months)
6000
8
5000
7
6
4000
5
3000
4
3
2000
2
1000
1
0
0
Flow (cfs)
# of months >10 mg/l Nitrate
9
2003
2001
1999
1997
1995
1993
1991
1989
1987
1985
1983
1981
1979
1977
1975
1973
1989
1986
1983
1980
1977
1974
1971
2001
1998
1995
Des Moines River
1992
0
1968
Nitrate mg/l
Nitrate Concentration
Raccoon River
12
10
8
6
4
2
Nitrate Transport
Raccoon River
Des Moines River
Nitrate Transport
(1,000 kg/day)
160
140
120
100
80
60
2001
1998
1995
1992
1989
1986
1983
1980
1977
1974
1971
1968
40
20
0
Nutrient Criteria
T N in rivers 2.62 mg/l
Data from 5/2000-03
DMR
Boone
DMR
Sayl
Rac R
Van
Meter
ave
7.89
7.25
8.52
8.38
8.19
6.45
min
1.36
1.41
1.24
3.00
3.46
1.40
max
17.0
14.4
17.7
15.3
14.6
11.4
9
5
4
0
0
2
n
44
44
44
44
44
44
%
20
11
9
0
0
5
#months
<2.62
DMR
DM
DMR
Runnells
DMR
Pella
Transport of Nutrients
and Effects of Reservoirs
Stations
1
5
10
6
7a
9
Discharge (cfs)
3,192
3,428
2,085
6,064
7,662
7,525
Suspended
solids
(1,000 kg/day)
1,623
389
3,328
3,932
5,027
600
Ammonia N
(kg/day)
1,084
1,497
915
3,256
3,156
3,669
Nitrate (kg/day)
66,000
67,000
46,000
125,000
145,000
125,000
Total phosphate
6,722
4,422
8,351
17,679
–
9,709
Water Year Mean
Stream Flow Separation and
Nitrate Nitrogen
(Schilling and Lutz)





Hydrograph separation using USGS program
HYSEP (Sloto and Crouse, 1996)
Regression analyses determined if annual Q vs P
relationship changed over time
Regression analyses of annual P, Q, Qb, Qs, and Q%
over time
Nitrate data summarized into monthly means
Regression and correlation of monthly mean nitrate
to streamflow components
Baseflow Discharge (in)
25
20
15
10
5
0
15
10
5
0
1900 1920 1940 1960 1980 2000
1900 1920 1940 1960 1980 2000
15
Baseflow Percentage
Stormflow Discharge (in)
Total Discharge (in)
Results – Streamflow Changes
10
5
0
1900 1920 1940 1960 1980 2000
80
70
60
50
40
30
20
1900 1920 1940 1960 1980 2000
Streamflow Changes, cont.



Annual precipitation also increased during
1916-2000 period
Regression residuals indicate change in
rainfall-runoff relationship since 1916
(p<0.05)
Thus, more precipitation is being routed into
streamflow as baseflow in latter portion of
20th century
Regression Models Relating
Baseflow to Nitrate
Mean Annual NO3-N Concentration
(mg/l)
Annual NO3-N Conc. Versus Baseflow Discharge (in)
14
y = 0.6202x + 3.9537
R2 = 0.6098
12
10
8
6
4
2
0
0
2
4
6
8
10
12
14
Discharge (in)
Qb provided best r2 value (0.61) compared to Q (0.59), Qs
(0.48) or Q% (0.27)
What role might
changing streamflow
hydrology in the
Raccoon River have
had on nitrate
concentrations?
NO3-N Concentration (mg/l)

16
14
12
10
8
6
4
1945-46
1972-2000
2
0
1
2
3
4
5
Log Mean Monthly Qb
12
NO3-N Concentration (mg/l)
Historical
Perspective
10
1972-2000
8
6
4
2
WY1946
0
1
2
3
Log Mean Annual Qb
4
5
Ammonia N

Sources
Biological degradation of organic matter
 Point source - wastewater effluent
 Nonpoint sources - fertilizer, feedlots


Importance
Oxidation of ammonia exerts an oxygen demand
 Unionized ammonia form toxic to aquatic life

/1
9
/1
9
77
77
77
/1
9
/1
9
3/
1/
19
2/
22
2/
15
77
77
77
77
25
20
15
250
Fish Kill Event
200
150
5
100
50
0
0
Flow cfs
Ammonia
2/
8/
19
2/
1/
19
/1
9
/1
9
77
Ammonia mg/l
10
1/
25
1/
18
/1
9
77
76
76
1/
4/
19
/2
8
/2
1
1/
11
12
12
Point Source Event 1977
Flow
400
350
300
/1
9
/1
9
77
77
77
/1
9
/1
9
3/
1/
19
2/
22
2/
15
77
77
77
77
18
400
16
350
14
300
12
250
10
Fish Kill Event
200
6
150
4
100
2
50
0
0
Flow cfs
Temperature
2/
8/
19
2/
1/
19
/1
9
/1
9
77
Temperature C
8
1/
25
1/
18
/1
9
77
76
76
1/
4/
19
/2
8
/2
1
1/
11
12
12
Point Source Event 1977
Flow
/1
9
/1
9
77
77
77
/1
9
/1
9
3/
1/
19
2/
22
2/
15
77
77
77
77
8
400
7
350
6
300
5
250
Fish Kill Event
200
3
150
2
100
1
50
0
0
Flow cfs
Total Phosphorus
2/
8/
19
2/
1/
19
/1
9
/1
9
77
Tot Phosphorus mg/l
4
1/
25
1/
18
/1
9
77
76
76
1/
4/
19
/2
8
/2
1
1/
11
12
12
Point Source Event 1977
Flow
Ammonia N
DMR below DM
Ammonia N
Flow
18
100000
16
10000
12
1000
10
8
100
6
4
10
2
0
Jul-71
1
Jul-74
Jul-77
Jul-80
Jul-83
Jul-86
Jul-89
Jul-92
Jul-95
Jul-98
Jul-01
Flow (cfs)
Ammonia N (mg/l)
14
Unionized Ammonia
Unionized
Ammonia
DMR
near
Boone
R River
near Van
Meter
DMR
below Des
Moines
DMR
near
Boone
R River
near Van
Meter
DMR
below Des
Moines
19672003
19722003
19712003
19992003
19722003
19992003
439
378
391
60
60
60
mean
0.009
0.006
0.015
0.002
0.004
0.004
Min
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
Max
0.267
0.093
0.373
0.013
0.040
0.026
%<0.016
13%
7%
27%
0%
3%
2%
Date
No. months
Phosphorus

Major sources
Nonpoint - fertilizers associated with sediment
 Point – wastewater & food processing plant effluents


Importance
Limiting nutrient (when N:P ratio >16:1)
 Can be re-suspended or released from sediments

Phosphorus Inputs
Human
1%
Industry
<1%
Manure
45%
Fertilizer
54%
Estimated Point versus Non-Point
Contributions to Stream P-Load
Point Source
20%
Non-Point
Source
80%
Jul-03
Jul-01
Jul-99
Jul-97
Jul-95
Jul-93
Jul-91
20
16
12
1000
10
8
100
6
4
10
2
0
1
Flow cfs
TPO4
Jul-89
Jul-87
Jul-85
Jul-83
Jul-81
Jul-79
Jul-77
Jul-75
Jul-73
Jul-71
Total Phosphate mg/l
Total Phosphate
Des Moines River below DM
Flow (cfs)
100000
18
10000
14
Total Phosphate
Des Moines River near Boone
TPO4
Flow (cfs)
20
100000
16
10000
12
1000
10
8
100
6
4
10
2
Feb-01
Feb-98
Feb-95
Feb-92
Feb-89
Feb-86
Feb-83
Feb-80
Feb-77
1
Feb-74
0
Flow cfs
14
Feb-71
Total Phosphate mg/l
18
Seasonal Kendall Tau Trend Analysis, Significant Trends (95%)
(from Monthly Mean Data, flow adjusted)
Total Phosphate
Tot Phosphate
n
mean
slope
Des Moines River near Boone
1971-2003
1971-1986
1999-2003
188
129
59
0.93
1.07
0.62
-0.013
no trend
-0.054
Tot Phosphate
n
mean
slope
Raccoon River near Van Meter
1972-2003
1972-1986
1999-2003
194
135
59
1.10
1.17
0.94
-0.004
0.017
no trend
Tot Phosphate
n
mean
slope
Des Moines River below Des Moines
1971-2003
1971-1986
1999-2003
207
148
59
1.98
2.15
1.57
-0.018
-0.038
no trend
1999-03 Phosphorus
DMR
Boone
DMR
Sayl
RR
Van
Meter
ave
0.05
0.10
0.11
0.46
0.47
0.18
min
0.01
0.01
0.01
0.10
0.11
0.04
max
0.39
0.40
0.49
2.08
1.19
0.45
ave
0.21
0.13
0.29
0.51
0.59
0.24
min
0.04
0.03
0.05
0.21
0.17
0.10
max
0.56
0.43
1.19
1.55
1.34
1.16
26
72
36
90
78
78
DMR
DM
DMR
Runnells
DMR
Pella
OP
TP
%OP
Nutrient Criteria
T P in rivers 0.118 mg/l
Data from 1999-03
DMR
Boone
DMR
Sayl
Rac R
Van
Meter
ave
0.21
0.13
0.29
0.51
0.59
0.24
min
0.04
0.03
0.05
0.21
0.17
0.10
max
0.56
0.43
1.19
1.55
1.34
1.16
8
4
6
0
0
1
n
59
59
59
59
59
59
%
14
7
10
0
0
2
#months
<0.118
DMR
DM
DMR
Runnells
DMR
Pella
Total Phosphorus
Saylorville Reservoir
Sediments
ave
Depth
(cm)
Water Content
(%)
Dry Bulk
Density
(g/cm3)
Head
8
241
0.33
946
Head
26
190
0.38
817
Dam
12
304
0.28
1232
Dam
22
220
0.35
1019
Dam
46
198
0.37
920
TP (mg/kg)
Cheney Reservoir, Kansas, USGS, Dam 647 mg/kg, Headwaters 477 mg/kg
For more information
dslutz@iastate.edu
http://www.ccee.iastate.edu/research/lutz/homepage.html
If interested contact me about statistical methods employed or see notes
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