Transcript Nutrient Trends in the Des Moines River

Long-term Monitoring of
the Des Moines River
Donna S. Lutz
Des Moines River Water Quality Network
Presented at the Des Moines Water Works January 28, 2008
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, 40 years at many sites, total of 252
parameters, about 485,000 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, & project webpage
Des Moines River Basin
•Length 535 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
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Physical
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Chemical
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temperature, flow/elevation
turbidity, secchi disc depth, gas saturation
dissolved oxygen, BOD, TOC, nutrients, suspended
solids
metals, pesticides
Biological
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chlorophyll pigments
bacteria
Important Programs: Short-term
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Bacteria
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River, reservoir and beaches
Is it safe to swim, wade?
State of Iowa WQ Stds
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Based on E Coli
Class A1 & A3 (1o & children)
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geomean 126 /100ml
Sample max 235 /100ml
Class A2 (2o contact)
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geomean 630/100ml
Sample max 2,880 /100ml
Bacteria Monitoring
Important Programs: Short-term
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Are they safe to eat?
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For people and critters
Cyprinus carpio
Fillets (28 yr) Whole (20 yr)
Dieldrin, Chlordane,
Heptachlor epoxide,
Alachlor, Trifluralin and
Chlorpyrifos
Electrofishing on Iowa River
Pesticides in Fish
Important Programs: Short-term
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Fish Kill Investigations
Thermal Stress
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Dorosoma cepedianum
Large kills, one species,
similar size
Gas Supersaturation
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Minor to large kills, many
species and size ranges
Either extreme gas
pressure or lowered
outflow
Important Programs: Short-term
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What’s Up?
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Why is water so foamy?
Oily?
Green?
Important Programs: Long-term
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What is normal?
Is water quality
improving? (degrading
or can’t tell?)
Major Players
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Nutrients
Pesticides
Chlorophyll
Bacteria
WQI
Significant Findings
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Non-point sources are the main contaminants;
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Point source loading has decreased
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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 have increased, with the greatest increases
seen 1967-1986, paralleling increases in N fertilizer use
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Total Phosphate levels have decreased slightly, but
only by about 0.01 mg/year
Significant Findings (cont’d)
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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
DMRWQN Website
http://te-webserver.cce.iastate.edu/research/lutz/dmrwqn/dmrwqn.html
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Project description, site photos
Monitoring event data, monthly &
annual reports
Beach bacteria data
Long-term data available from Lutz or
website
Acknowledge source, ie RI Corps
 Provide us with analysis or report
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Monitoring Event Report
Annual Report
Focus on Nitrite +Nitrate N
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Ammonia oxidized to nitrate (bacterially mediated)
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Sources
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Nitrite, intermediate product, (1967-76, max 0.68 mg/l, 99%
of samples <0.20 mg/l)
Fertilizers, oxidation or organic N, fixation of N2,
precipitation, sewage effluents
Losses
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Leaching, assimilation living organisms, conversion to other
forms
Soluble, easily leaches from soil
TRANSFORMS & MOVES with WATER
Nitrate vs Flow, Raccoon River near Van Meter
7.07 mg/l 2,078 cfs
Nitrate
12
12000
10
10000
8
8000
6
6000
4
4000
2
2000
0
0
Flow (cfs)
Nitrate (mg/l as N)
Flow
2007
2005
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 = 0.627
10
9
Nitrate (mg/l)
8
7
6
5
4
3
2
1
0
0
2000
4000
6000
Flow (cfs)
8000
10000
12000
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
Regression Models Relating
Baseflow to Nitrate
Qb provided best r2 value (0.61) compared to Q (0.59), Qs
(0.48) or Q% (0.27)
What is normal?
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Des Moines River at Boone
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40 yr annual average, 5.86 mg/l
Raccoon River at Van Meter
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35 yr annual average, 7.07 mg/l
→ Was 2007 water year unusual?
DMR 7.11 mg/l Raccoon R 9.58 mg/l
Are nitrate concentrations
increasing?
Need to use statistical techniques
to discern and describe trends
Data is not normally distributed so
used non-parametric statistics
 Loftis and Ward, Colorado State
University - tested 7 statistical tests
Recommend Seasonal Kendall test
Data was flow-adjusted – influence
of climatic events removed
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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
1972-2007
1972-1986
1986-1997
425
163
133
6.16
6.21
6.00
no trend
no trend
no trend
1997-2007
129
6.36
+0.26
NO2+NO3 N
n
mean
slope
Raccoon River near Van Meter
1972-2007
1972-1986
1986-1997
377
163
133
7.07
6.83
7.22
+0.05
+ 0.21
no trend
1997-2007
129
7.81
+0.15
180
16
160
14
140
12
120
10
100
8
80
6
60
40
20
0
Ia N Use
Ia Corn Acres
4
2
0
Corn Acres
Lbs/acre
Nitrogen Fertilizer Use and Corn Acres Planted 1964- 2006
Raccoon R at Van Meter, Recent data shows increasing trend 0.14 mg/l/yr
*but only at 90% confidence
DMR at Boone, Recent data shows increasing trend 0.26 mg/l/yr
Exceedance vs Flow, Des Moines River at Boone
months
12000
8
10000
7
6
8000
5
6000
4
3
4000
2
2000
1
0
0
Flow (cfs)
# of months >10 mg/l Nitrate
9
2006
2004
2002
2000
1998
1996
1994
1992
1990
1988
1986
1984
1982
1980
1978
1976
1974
1972
1970
1968
Exceedance vs Flow, Raccoon River at Van Meter
months
9
# of months >10mg/l Nitrate
8
7
6
5
4
3
2
1
0
flow
Linear (months)
6000
5000
4000
3000
2000
1000
0
What this means to DMWW
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Nitrate concentrations are
increasing in the Raccoon
River, currently at a rate of
0.15mg/l/yr
Is the 10 mg/l drinking water
standard being exceeded more
often? Yes, in the Des Moines
River, maybe in the Raccoon
River.
Overall, is water quality better?
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Yes, according to WQI
DMR WQI based on
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%DO (0.21)
pH (0.14)
BOD (0.14)
NO2+NO3 (0.13)
Ammonia (0.17)
Turbidity + Sus Solids (0.21)
For more information
[email protected]
http://www.ccee.iastate.edu/research/lutz/homepage.html
If interested contact me about statistical methods employed