processes controlling the source, movement, and release of soil phosphorus in midwestern streams...
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College of Agriculture and Life Sciences
Processes Controlling the Source, Movement, and Release of Soil Phosphorus in Midwestern Streams
Richard Schultz, Thomas Isenhart, and Michael ThompsonIowa State University
Mark Tomer and John KovarUSDA – National Laboratory for Agriculture and Environment
Keith SchillingIIHR - Iowa Geological Survey
USDA-AFRI Foundational Program
Iowa Nutrient Reduction Strategy
• Stream banks are known to be a potentially large source of stream sediment.
• However, accurately accounting for stream bank sources of P is extremely difficult.
• Therefore, evaluating strategies to reduce P losses from eroding stream banks are beyond the scope of this effort.
Phosphorus Transport in Iowa Streams: The Importance of Stream Bed and Bank Erosion
Altered hydrology
Tile drainageChannelization
Severely & Very Severely Erosive Banks (USDA-NRCS, 1998)
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Percent Total Channel Length Classified as Erosive, by Year
Channel Cross-Sectional Area
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Distance (m)
0 2 4 6 8 10 12
Elevation (m
)
-3.5
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
20141998
1998
2014
Change in Cross-Sectional Area, 1998-2014
Change in Cross-Sectional Area, 1998-2014
Distance downstream (km)0 2 4 6 8 10 12 14
Percent change
-20
0
20
40
60
80
IncreaseDecrease
Recession Rates
Full Set Biannually
Focus Set Monthly, or by Flow Event
Robert’s Creek Member
3500 – 500 YBP
Gunder Member10,500 – 4500 YBP
Camp Creek Member
400 YBP - Present
Slump Material
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Recession Estimation with LiDAR
Assessing In-Channel Sediment Storage
Bankfull
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In-Channel Sediment Storage by Feature
Event Sampling at Guage Stations
Silt Loams, Coarser with Depth
Camp Creek Roberts Creek
Gunder Till
Photo courtesy of John L Kovar
Sediments pHOM Sand Silt Clay Fe-CBD Fe-ox Ca-M3
---------------- % --------------- -------------mg/kg-----------
Camp Creek 6.2 3.4 11 63 25 6,825 3,348 1,975
Roberts Creek
6.3 4.5 13 60 27 5,682 3,947 2,983
Gunder 7.4 1.5 6 72 22 3,813 1,967 2,135
Till 8.1 1.7 49 31 21 10,124 743 6,750
Stream Bank Soil Characteristics
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Sequential Phosphorus Extraction
Soils Sampled for P Adsorption-Desorption Studies
Upland restoration, yet no trends in sediment load, eroding streambank length, streambank recession rate
Observed Processes
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Simon and Hupp, 1986, Simon and Rinaldi, 2006
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Tentative Conclusions
Entire study reach within Stage IVSimon and Hupp, 1986, Simon and Rinaldi, 2006
Slow transition from initial 20th century disturbance
Simon and Rinaldi, 2000 (could take 40-100+ years)
Cohesive Gunder bed and banks
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Distance downstream (km)0 2 4 6 8 10 12
m3 m
-1
1.21.41.61.82.02.22.42.62.83.03.2
Channelized Meandering
Total In-Channel Sediment Storage
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November 2014
March 2015
April 2015
May 2015
June 2015
July 2015
August 2015
September 2015
October 2015
Volume (m
3 )
0
200
400
600
800
1000
1200
1400
1600
1800
Walnut Creek Cumulative Streambank ErosionCumulative Streambank Erosion
Volu
me
(m3 )
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Image adapted from Schilling et al., 2012
Walnut Creek Watershed
• Perennial, third order stream
• 5218 ha
• Agricultural headwaters, subsurface drainage
• Extensive channelization
• Water Quality Data 1995 –
• Neal Smith NWR (2225 ha)• 1991 - Present
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Distance (m)
0 2 4 6 8 10 12
Elevation (m
)
-3.5
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
20141998
1998
2014
Change in Cross-Sectional Area, 1998-2014