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Water quality replicate sample results, June 2008.

 
Replicate no./ Flow condition Site name Date Type Ammonia Nitrate TN† Ortho-P TP SS
mg L−1
1 Receding limb Iowa River at Iowa City, IA 05454500 06/20/2008 11:20 EWI 0.04 3.77 4.30 0.18 0.34 488
Iowa River at Iowa City, IA 05454500 06/20/2008 11:25 GRAB 0.05 3.74 4.33 0.18 0.28 38
2 Receding limb (later) Iowa River near Lone Tree, IA 05455700 06/26/2008 10:45 EWI 0.02 3.80 4.37 0.19 0.28 67
Iowa River near Lone Tree, IA 05455700 06/26/2008 11:10 GRAB <0.01 3.82 4.45 0.20 0.28 44
TN, total nitrogen; Ortho-P, orthophosphate; TP, total phosphorus; SS, suspended sediment.



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Summary statistics for concentrations of selected constituents near peak flow in major rivers during extreme high-flow conditions, June 2008.

 
Major river basin No. of sites Statistic Ammonia Nitrate TN† Ortho-P TP SS
mg L−1
Turkey River‡ 1 Value 0.081 5.06 7.86 0.171 1.10 1880
§
Maquoketa River‡ 1 Value 0.123 3.68 7.67 0.170 1.35 2570
§
Wapsipinicon River 2–3 Median 0.043 5.18 6.38 0.102 0.387 102
Standard deviation 0.067 0.12 0.62 0.011 0.224 57
Iowa River 11 Median 0.032 4.79 6.14 0.183 0.423 239
Standard deviation 0.025 0.65 1.24 0.028 0.242 258
Skunk River 4 Median 0.022 3.78 4.89 0.146 0.520 250
Standard deviation 0.010 0.88 1.07 0.072 0.175 228
Des Moines River 6–8 Median 0.052 5.50 6.70 0.166 0.415 260
Standard deviation 0.024 1.34 1.11 0.069 0.173 260
Mississippi River 2–3 Median 0.042 3.91 4.90 0.117 0.350 152
Standard deviation 0.035 0.53 0.04 0.021 0.080 80
Median of all samples 0.042 4.79 6.14 0.166 0.423 237
TN, total nitrogen; Ortho-P, orthophosphate; TP, total phosphorus; SS, suspended sediment.
indicates equal-width increment samples.
§ indicates single samples with no corresponding summary statistics.



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Comparison of concentrations and daily loads near peak flow in June 2008 and June 1979 to 2007.

 
Constituent† Statistic Concentration Daily load
1979–2007 2008 1979–2007 2008
mg L−1 kg d−1
Ammonia No. of sites 19 19
mean 0.060 0.054 4,300 8,400
median 0.030 0.033 200 5,600
p-value (paired t test) p = 0.70 p = 0.001
Nitrate No. of sites 19 19
mean 9.86 4.70 184,000 745,000
median 8.40 4.79 38,400 395,000
p-value (paired t test) p = 0.001 p = 0.001
Ortho-P No. of sites 19 19
mean 0.091 0.161 3,200 23,700
median 0.090 0.170 400 13,300
p-value (paired t test) p < 0.001 p < 0.001
TP No. of sites 17 17
mean 0.296 0.586 11,800 80,600
median 0.335 0.423 1,000 48,200
p-value (paired t test) p = 0.01 p = 0.002
TN No. of sites 10 10
mean 14.8 6.87 122,000 642,000
median 11.4 6.93 56,000 416,000
p-value (paired t test) p = 0.001 p = 0.01
SS No. of sites 16 16
mean 332 523 14,600,000 59,900,000
median 196 250 2,650,000 19,800,000
p-value (paired t test) p = 0.44 p = 0.004
Ortho-P, orthophosphate; TP, total phosphorus; TN, total nitrogen; SS, suspended sediment.



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Daily yields for 29 eastern Iowa sites near peak flow in 2008. Italics indicate the six largest loads for each constituent.

 
Map # STAID† Name Drainage Area Daily Peak Flow TN TP SS
km2 m3 s−1 kg km−2 d−1
1 05412500 Turkey River at Garber, IA‡ 4,002 1,010 172 24.1 41,100
2 05418600 Maquoketa River near Spragueville, IA‡ 4,227 787 123 21.7 41,300
3 05420500 Mississippi River at Clinton, IA 22,1703 5,180 0.525 214
4 05420680 Wapsipinicon River near Tripoli, IA 896 351 239 22.0
5 05421740 Wapsipinicon River near Amamosa, IA 4,079 878 119 7.19 2,660
6 05422000 Wapsipinicon River near De Witt, IA 6,050 923 76.8 2.70 817
7 05451070 South Fork Iowa River Headwaters near Blairsburg, IA 7 1.39 152 14.7 9,070
8 05451080 South Fork Iowa River near Blairsburg, IA‡ 31 15.7 353 44.2 40,700
9 05451210 South Fork Iowa River NE of New Providence, IA‡ 580 166 168 18.6 10,800
10 05451500 Iowa River at Marshalltown, IA 3,968 151 73.7 5.73 3,150
11 05453100 Iowa River at Marengo, IA 7,236 1,240 66.8 6.29 2,110
12 05453520 Iowa River below Coralville Dam near Coralville, IA 8,068 1,100 72.4 3.20 625
13 05454500 Iowa River at Iowa City, IA 8,472 1,160 69.2 3.22 626
14 05455700 Iowa River at Lone Tree, IA 11,119 1,470 62.0 4.83 1,370
15 05464765 Cedar River at Highway 30 near Bertram, IA 18,026 3,910 97.2 7.30 6,310
16 05465000 Cedar River near Conesville, IA 20,168 3,370 87.7 8.46 3,450
17 05465500 Iowa River at Wapello, IA 32,375 4,500 73.8 4.80 2,150
18 05469720 Mississippi River at Burlington, IA 295,259 12,200 17.4 1.25 544
19 05472010 South Skunk River below Lake Keomah near Oskaloosa, IA 4,369 481 51.6 3.90 1,710
20 05472500 North Skunk River near Sigourney, IA 1,891 255 74.2 7.35 3,090
21 05473450 Big Creek north of Mt. Pleasant, IA 150 47.3 119 20.4 18,400
22 05474000 Skunk River at Augusta, IA 11,168 1,220 37.6 3.67 2,210
23 05474500 Mississippi River at Keokuk, IA 308,209 11,700 16.2 1.38 859
24 05481950 Beaver Creek near Grimes, IA 927 174 66.2 8.75 5,510
25 05482000 Des Moines River at second Avenue at Des Moines, IA 16,174 1,320 51.1 2.13 720
26 05482300 North Raccoon River near Sac City, IA 1,813 7,890 94.0 5.54
27 05482500 North Raccoon River near Jefferson, IA 4,193 17,300 76.1 4.84
28 05485500 Des Moines River below Raccoon River at Des Moines,IA 25,586 2,800 65.7 6.71 7,210
29 05488500 Des Moines River near Tracy, IA 32,320 2,920 46.9 1.73 343
30 05489500 Des Moines River at Ottumwa, IA 34,638 2,860 43.0 1.56 1,280
31 05490500 Des Moines River at Keosauqua, IA 36,358 2,970 45.5 2.47 2,470
STAID, station ID number.
Indicates equal-width increment samples.



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Nitrogen and phosphorus transported to the Mississippi River from eastern Iowa during the 16-d (10–25 June 2008) storm in June 2008.

 
Site name/Station ID no. Discharge TN† TP SS
m3 s−1 kg
Wapsipinicon River near De Witt, IA 05422000 8,871 4,860,000 163,000 74,800,000
Iowa River at Wapello, IA 05465500 42,577 22,000,000 1,300,000 564,000,000
Skunk River at Augusta, IA 05474000 12,632 4,990,000 408,000 272,000,000
Des Moines River at Keosauqua, IA 05490500 33,932 17,700,000 1,040,000 1,040,000,000
Total 98,000 49,500,000 2,900,000 1,950,000,000
TN, total nitrogen; TP, total phosphorus; SS, suspended sediment.



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Comparison of yields from the 16-d flood event in 2008 with annual yields estimate by Goolsby et al. (1999) and Robertson et al. (2009) calculated for three basins in eastern Iowa. Note that the Des Moines River site used in Goolsby et al. (1999) is Des Moines River at Francisville, MO (05490600), approximately 50 km downstream from Keosauqua, IA.

 
Site name/Station ID no. 2008 WY Q† WY annual mean Q Flood % of annual mean Q Constituent‡ Flood 16-d yield Annual yield
Goolsby et al. (1999) Robertson et al. (2009)
Yield Flood % of avg. annual yield Yield Flood % of avg. annual yield
m3 s−1 kg km−2 kg km−2
Des Moines River at Keosauqua, IA 05470500 529 244 46 TN 486 1850 26 1910 26
TP 28.7 64.1 45 73.7 39
Nitrate 421 1690 25
Ortho-P 11.3 37.1 30
Iowa River at Wapello, IA 05465500 616 267 43 TN 679 2290 30 2210 31
TP 40.1 94.9 42 87.2 46
Nitrate 546 1770 31
Ortho-P 17.6 62.3 28
Skunk River at Augusta, IA 05474000 198 74 37 TN 447 2020 22 2060 22
TP 36.5 120.5 30 111.7 33
Nitrate 400 1560 26
Ortho-P 14.0 41.7 34
WY, water year; Q, discharge.
TN, total nitrogen; TP, total phosphorus; Ortho-P, orthophosphate.