Prioritizing watersheds for BMP placement: southern Minnesota 

case studyLori Krider, PhD. Candidate

Dr. Bruce Wilson, Professor

Department of Bioproducts and Biosystems EngineeringUniversity of Minnesota

Water quality issues  Agriculture and drainage  Watershed approach Case study Mullenbach Two‐Stage Ditch

Stability and nitrates

Overview

Restoration vs. Protection

Basin Overview

stormwater.pca.state.mn.us

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.comWHY?‐climate change‐river bluffs‐agricultural practices

Minnesota River

Mississippi River

fws.gov

Types of Drainage SystemsSurface Drainage:Ditches ‐ remove standingwater (outlet for tiles)

Subsurface Drainage:“Tiles” ‐ remove water from soil

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):

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

Changes in Row Crop Acreages A

crea

ge o

f Cro

ps (i

n th

ousa

nds)

Year

1870 1890 1910 1930 1950 1970 1990 20100

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

MN AESMN AES

FertilityManure 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 1990 2010

N A

pplic

atio

n R

ates

(lb/

ac)

0

20

40

60

80

100

120

140

160Decrease in row spacing

Minnesota Pollution Control Agency (MPCA) Intensive Watershed Monitoring  

Watershed Approachmpca.state.mn.us

Watershed Restoration and Protection Strategy (WRAPS)

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

BMP Placement

Tomer, 2013Tomer, 2013

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

MPCA Nutrient Reduction Strategy (Sept 2014) Mississippi River

Nutrient Management

pca.state.mn.us

Part of the solution is agricultural BMPs‐bioreactors‐two‐stage ditches‐WASCOBs‐cover crops, etc . . . 

Cedar River Watershed

Case Study

75% row crops

Mullenbach Two‐Stage Ditch Constructed Oct 2009

Kramer, 2011

Mower County

Case Study

Kramer, 2011

Funding: MPCAData: 2009 ‐ 2013

Two-Stage Design

bayjournal.com

* Bank sloughing* Reduced sediment transport* Limited water treatment

Conventional: 

* Steady, uniform flow* Larger wetted perimeter, surface area* Smaller average bed shear 

Two‐Stage Designs: 

Natural Processes

Stage 1: Low Flow Channel

Stage 2: High Flow Channel

Stability

Analyses

Cross-Sectional Profiles

92

94

96

98

100

102

104

106

108

110

112

0 10 20 30 40 50 60 70 80 90

Elevation (ft)

Distance from east stake (ft)

Location40+04

Pre‐ConstructionApr‐09Oct‐10

Apr‐12

Nov‐13

Cross-Sectional Surveys

0

2

4

6

8

10

12

14

300 600 900 1200 1800 2100 2400 2700 3000 3300 3600 4200 4500 4800 5100 5400 5700 6000

Chan

nel W

idth (f

t)

Station (ft)

Bankfull Width Increased by ~11% ‐ less active sediment supply

9092949698

100102104106108

0 1000 2000 3000 4000 5000 6000

Ele

vatio

n (ft

)

Channel Distance (ft)

bed riffle pool

9092949698

100102104

0 1000 2000 3000 4000 5000 6000

Ele

vatio

n (ft

)

Channel Distance (ft)

Pool BedRiffle

Thalweg Longitudinal ProfilePre‐Construction:* 5 pool‐riffles

November, 2013:* 65 pool‐riffles

sorting larger particlescleaning out finer particles

October, 2010:* 0.5 ft aggradation* More pool‐riffles

From Brenda DeZiel

Fish Community

Low DO Need sand/gravel DegradationFIBI: 44 ‐> 52.5 (+8.5)574 ‐> 1050 individuals

Daily nitrate and precipitation: April 27 – Oct 10, 2010

Nitrate Concentration

ΔC~ 4 mg/L

Nitrate Removal (denitrification)

• Mass balance (in‐stream)

• N2O laboratory 

– Acetylene inhibition assay 

– Sediment

Approaches:

Mass Balance Method

UpstreamQin

[N]in[δ18O]in

DownstreamQout

[N]out[δ18O]out

GroundwaterQgw

[N]gw[δ18O]gw

NremovedTiles

Qtile

[N]tile[δ18O]tile

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

Percen

t Rem

oval of N

Groundwater NO3‐N Concentrations

Large Groundwater Contribution(δ18O= ‐9)

Modest Groundwater Contribution(δ18O= ‐10)

Mass Balance Results

Mass Balance Results(September 18, 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

140Nitr

ate‐

N (m

g/L)

September 18

September 20

1 source?

2nd source?September 21, 2011* Entire ditch length* 8.78 kg N per day* 34%

Acetylene InhibitionNitrification

NH3+

NO2‐

NO3‐

DenitrificationNO2

‐ NO N2O N2

Acetylene Method(laboratory)

In‐situ Method* Lab measurement of N2O

Laboratory Results

0

20

40

60

80

Benches East Riparian West Riparian Channel

Den

itrifica

tion Ra

tes

(mg N

2O‐N m

‐2h‐

1 )

South 

North 

Removal Rate* Entire Ditch* 8.84 kg N/ day

Linear Wetland Nitrate Removal

Enhanced Ditch Nitrogen Removal

200 ft

0

5

10

15

20

25

30

35

Nitr

ate‐N (m

g/L)

In (28+00 tile) Out (30+00)

Reduced by ~ 1 ‐ 2 mg/L(5 – 10%)

• Two‐stage ditch is stable

• In‐stream habitat improvement

• Shows potential for substantial biotic function

• Nitrate removal between 10% and 30%

Summary

Questions and Comments