Nutrient and sediment concentrations and corresponding loads during the historic June 2008 flooding in eastern Iowa U.S. Department of the Interior U.S. Geological Survey June 2008 flooding in eastern Iowa L.E. Hubbard 1 , Kolpin, D.W. 1 , Kalkhoff, S. J. 1 , Robertson, D. M. 2 (1) U.S. Geological Survey, Iowa Water Science Center (2) U.S. Geological Survey, Wisconsin Water Science Center
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Nutrient and sediment concentrations and corresponding ...2008 Steve Kalkhoff. Summary Concentrations may be similar to average concentrations but loads are much larger during extreme
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Nutrient and sediment concentrations and corresponding loads during the historic June 2008 flooding in eastern Iowa
U.S. Department of the InteriorU.S. Geological Survey
June 2008 flooding in eastern Iowa
L.E. Hubbard 1, Kolpin, D.W. 1, Kalkhoff, S. J. 1, Robertson, D. M. 2
(1) U.S. Geological Survey, Iowa Water Science Cent er(2) U.S. Geological Survey, Wisconsin Water Science Center
6/12/2008 Cedar Rapids 3rd Ave
6/13/2008 Cedar Rapids
6/12/2008 Cedar RapidsPhoto by Jason McVay
6/13/2008 Cedar River at Hwy 30Photo by Scott Strader
6/9/2008 Charles City, IA (Cedar River) Photo by Jon Nania
Coralville, IA (Iowa River)
� December 2007 to May 2008 - 2 nd wettest in the period of record for eastern Iowa (1895 to 2008) (NCDC, 2008)
� Concurrent grab samples and EWI were collected at two sites at different discharges to document sample bias
Methods
� Samples were analyzed for total phosphorus (TP), total nitrogen (TN), nitrate, ammonia, orthophosphate (ortho-P), and suspended sediment (SS)
� Data Analysis� Data Analysis� Concentrations and Instantaneous loads� 16-day transport yields - four Mississippi River
tributaries� Percentage of the annual yield - three sites
according to two different study estimates.
10
15
20
25
Con
cent
ratio
n (m
g/L)
Nitrate (mg/L)
Total Nitrogen (mg/L)
SS*100 (mg/L)
0
5
Con
cent
ratio
n (m
g/L)
1 2-31 11 4 6 2-3
† indicates EWI sample
0.4
0.6
0.8
1
1.2
1.4C
once
ntra
tion
(mg/
L)
Ammonia (mg/L)
Ortho-p (mg/L)
Total Phosphorus (mg/L)
0
0.2
0.4
Con
cent
ratio
n (m
g/L)
† indicates EWI sample
1 2-31 11 4 6 2-3
Results
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
Con
cent
ratio
n (m
g/L)
Ammonia
Ortho-p
Total P
0
10000
20000
30000
40000
50000
60000
Load
(kg
/hr)
Ammonia
Ortho-p
Total P
P<0.05
P<0.05
P<0.05
P>0.05
P<0.05
P<0.05
998239 430
48,200
5,580
13,300
0
1 2
0
5
10
15
20
25
30
1 2
Con
cent
ratio
n (m
g/L)
Nitrate
Total N
SS*10
0
1 2
0
500,000
1,000,000
1,500,000
2,000,000
2,500,000
1 2
Load
(kg
/hr)
Nitrate
Total N
SS*10
1979-2007 1979-2007
1979-2007 1979-2007
2008 2008
2008 2008
P<0.05
P>0.05
P<0.05
P<0.05
P<0.05
P<0.05
38,40056,000
265,000395,000
416,000
1,980,000
Results – TN Near Peak Daily Yields
Results – TP Near Peak Daily Yields
Results – SS Near Peak Daily Yields
Results� 16-day TN transport load could fertilize
843,000 acres of cropland – over 6 counties � 16- day TP could fertilize 152,000 acres� 16-day SS could fill 143,000 dump trucks
Site Name Discharge TN TP SSSite NameSTAID
Discharge(m3/s)
TN(kg)
TP(kg)
SS(kg)
Wapsipinicon River near De Witt, IA05422000
8,870 4,860,000 163,000 7.48 E7
Iowa River at Wapello, IA05465500
42,600 22,000,000 1,300,000 5.64 E8
Skunk River at Augusta, IA05474000
12,600 4,990,000 408,000 2.72 E8
Des Moines River at Keosauqua, IA05490500
33,900 17,700,000 1,040,000 1.04 E9
Total 98,000 49,500,000 2,900,000 1.95 E9
Results – 16-day Yields
Site NameSTAID
2008 WY
(m3/s)
WY Annual Mean (m3/s) Constituent
Flood 16-day Yield
Annual Yield
Yield (kg/km2)
Goolsby (1999)* Robertson et al. (2009)
Yield (kg/km2)
Flood % of annual yield
Yield (kg/km2)
Flood % of annual yield
Note: the Des Moines River site used in Goolsby et al. (1999) is Des Moines River at Francisville, MO (05490600), approximately 50 km downstream of Keosauqua, IA
1993 vs. 2008� Daily peak-flow was higher in 2008� Different hydrographs
175,000
200,000
Iowa River at Wapello, Ia
Dai
ly m
ean
disc
harg
e, in
cub
ic fe
et p
er s
econ
d
1993
0
25,000
50,000
75,000
100,000
125,000
150,000
175,000
Dai
ly m
ean
disc
harg
e, in
cub
ic fe
et p
er s
econ
d
Jan Feb Mar Apr May Jun Jul Aug Sep
19932008
Steve Kalkhoff
Summary
� Concentrations may be similar to average concentrations but loads are much larger during extreme events
� Floods very important to average annual yield – 2008 flood up to 46% of average annual – 2008 flood up to 46% of average annual yield!
� Implications of Midwest flooding to the Gulf of Mexico hypoxic zone� Lasting effects of 1993 on the Gulf hypoxic zone� July 2008 hypoxic zone ranks 2 nd
Future Work
� Each flood is different� Need more data – characterizing floods and