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![Mass Balance Method
Upstream
Qin
[N]in
[δ18O]in
Downstream
Qout
[N]out
[δ18O]out
Groundwater
Qgw
[N]gw
[δ18O]gw
Nremoved
Tiles
Qtile
[N]tile
[δ18O]tile](https://image.slidesharecdn.com/nmefckriderwilson12-1-15final-151209175330-lva1-app6892/75/Krider-Prioritizing-Watersheds-for-PMP-Placement-26-2048.jpg)
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Krider - Prioritizing Watersheds for PMP Placement
The document summarizes a case study on prioritizing watersheds for best management practices (BMPs) placement in southern Minnesota. It discusses: - Water quality issues related to agriculture and drainage systems increasing nitrates and sediment in the Minnesota River watershed - A watershed approach being taken by state agencies to monitor watersheds and implement restoration strategies - A case study of a two-stage ditch construction project in Mower County that showed stability over time, increased habitat, and 10-30% nitrate removal.
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Krider - Prioritizing Watersheds for PMP Placement
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- 2. Water quality issues Agriculture and drainage Watershed approach Case study Mullenbach Two‐Stage Ditch Stability and nitrates Overview
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- 4. Minnesota River: CAFOs, fertilizer pollution, row crops, erosion Nitrates and sediment Water Quality Issues in S MNEPA SPARROW, 2013 (mrbdc.mnsu.edu) 19.9 mil lbs/yr 18.2 mil lbs/yr 10.1 mil lbs/yr (Mattteson& Baskfield, ND) startribune.com WHY? ‐climate change ‐river bluffs ‐agricultural practices Minnesota River Mississippi River
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- 6. Why Drainage? • Decreased maintenance of transportation • Increased crop yields •Increased land value • Reduced risk of malaria Illinois had settlements abandoned because of malaria in 1830s Fort Snelling: 66 cases per 1000 people per year (1829‐1838) Palmer (1915):
- 7. Ditch Construction: Blue Earth, Brown, Le Sueur, & Nicollet County 0.00% 5.00% 10.00%15.00% 20.00% 25.00% 30.00% Prior to 1880 1900-1909 1920-1929 1940-1949 1960-1969 Quade et al., 1980 Above average precipitation ‐> greater ditch construction Drought First Second
- 8. Changes in Row Crop Acreages AcreageofCrops(inthousands) Year 1870 1890 19101930 1950 1970 1990 2010 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 Corn Soybeans Data Provided by Steven Taff Increasing commodity prices and growing populations 100% yield increase
- 9. MN AES MN AES Fertility Manure Application Rates: 1930’s: 8 tons/ac, 1950’s: 6.2 tons/ac, 1970’s: 4 tons/ac (V. Cardwell) More row crops ‐> less livestock David Hansen Constituents known and constant Commercial Fertilizers: 1950’s: 14%, 1960’s: 67% and 1979: 95% (V. Cardwell) Year 1950 1970 19902010 NApplicationRates(lb/ac) 0 20 40 60 80 100 120 140 160 Decrease in row spacing
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- 11. Minnesota Pollution Control Agency Intensive Watershed Monitoring & WRAPS Board of Water and Soil Resources (BWSR) Targeted Watersheds: grants to local governments 1 Watershed, 1 Plan: integration Watershed Approach bwsr.state.mn.us
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- 13. MPCA Sediment Reduction Strategy (Jan 2015) Minnesota and Lower Mississippi River 50 percent reduction by 2030 90 percent reduction by 2040 Sediment Management mpca.state.mn.us
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- 16. Mullenbach Two‐Stage Ditch Constructed Oct 2009 Kramer, 2011 Mower County Case Study Kramer, 2011 Funding: MPCA Data: 2009 ‐ 2013
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- 20. Cross-Sectional Profiles 92 94 96 98 100 102 104 106 108 110 112 0 1020 30 40 50 60 70 80 90 Elevation (ft) Distance from east stake (ft) Location 40+04 Pre‐Construction Apr‐09Oct‐10 Apr‐12 Nov‐13
- 21. Cross-Sectional Surveys 0 2 4 6 8 10 12 14 300 600900 1200 1800 2100 2400 2700 3000 3300 3600 4200 4500 4800 5100 5400 5700 6000 Channel Width (ft) Station (ft) Bankfull Width Increased by ~11% ‐ less active sediment supply
- 22. 90 92 94 96 98 100 102 104 106 108 0 1000 20003000 4000 5000 6000 Elevation(ft) Channel Distance (ft) bed riffle pool 90 92 94 96 98 100 102 104 0 1000 2000 3000 4000 5000 6000 Elevation(ft) Channel Distance (ft) Pool BedRiffle Thalweg Longitudinal Profile Pre‐Construction: * 5 pool‐riffles November, 2013: * 65 pool‐riffles sorting larger particles cleaning out finer particles October, 2010: * 0.5 ft aggradation * More pool‐riffles
- 23. From Brenda DeZiel Fish Community Low DO Need sand/gravelDegradation FIBI: 44 ‐> 52.5 (+8.5) 574 ‐> 1050 individuals
- 24. Daily nitrate and precipitation: April 27 – Oct 10, 2010 NitrateConcentration ΔC~ 4 mg/L
- 25. Nitrate Removal (denitrification) •Mass balance (in‐stream) • N2O laboratory – Acetylene inhibition assay – Sediment Approaches:
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- 27. August 3, 2010 – entire ditch length Groundwater δ18O and NO3 unknown 0 5 10 15 20 25 30 35 40 45 15 20 25 30 35 40 Percent Removal of N Groundwater NO3‐N Concentrations Large Groundwater Contribution (δ18O= ‐9) Modest Groundwater Contribution (δ18O= ‐10) Mass Balance Results
- 28. Mass Balance Results (September18, 2013, 51+00 to 53+73, ΔQ=0.13 cfs, Qus = 1 cfs) Single groundwater source: 14.6% (6.5 kg N/day) Two groundwater sources: 16% (7.23 kg N/day) 0 20 40 60 80 100 120 140Nitrate‐N (mg/L) September 18 September 20 1 source? 2nd source?September 21, 2011 * Entire ditch length * 8.78 kg N per day * 34%
- 29. Acetylene Inhibition Nitrification NH3 + NO2 ‐ NO3 ‐ Denitrification NO2 ‐ NON2O N2 Acetylene Method (laboratory) In‐situ Method * Lab measurement of N2O
- 30. Laboratory Results 0 20 40 60 80 Benches EastRiparian West Riparian Channel Denitrification Rates (mg N2O‐N m‐2h‐1) South North Removal Rate * Entire Ditch * 8.84 kg N/ day
- 31. Linear Wetland NitrateRemoval Enhanced Ditch Nitrogen Removal 200 ft 0 5 10 15 20 25 30 35 Nitrate‐N (mg/L) In (28+00 tile) Out (30+00) Reduced by ~ 1 ‐ 2 mg/L (5 – 10%)
- 32. • Two‐stage ditch is stable • In‐stream habitat improvement •Shows potential for substantial biotic function • Nitrate removal between 10% and 30% Summary
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