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The influence of the two‐stage ditch on water quality in an agricultural landscapewater quality in an agricultural landscape
Jennifer L. Tank
Department of Biological Sciences
fUniversity of Notre Dame
Streams draining row crop agriculture export excess nutrients and sediments
Conventional channelized stream
unstable banks Fertilizer
SedimentNO3
‐ .
sub‐surface tile drain
• In Indiana, >90% of the over 50,000 km of stream/ditches are located within 500 m of a row‐crop field. p
• Fertilizer addition, channelization, and tile drainage improve crop yields, but these practices also reduce nutrient retention and channel stability.
Net Result: drainage modification results in increased export of excess nutrients and sediments to downstream water bodies.
Agricultural activity and the export of excess nutrients result in algal blooms followed by hypoxia
Excess Nutrients
Algal Blooms
Algal Death & Decomposition
Water Column HypoxiaGulf of Mexico (N)
• Peak run‐off often occurs during spring snowmelt and storms.
Lake Erie (P)
New in‐stream management tool: two‐stage ditch
Channelized
During late-fall construction
Mature floodplain benches (6 yrs post)
• Increase channel stability
• increased sedimentation → particles settle out on floodplainsout on floodplains
• We predict increased nutrient retention→ more time/space for removal
Two‐Stage Ditch Monitoring Multiple two-stage sites
1. Can we reduce sediment and phosphorus export?
2 Can we increase nitrate N removal?
Receiving SystemLake ErieOhio RiverMississippi R.
2. Can we increase nitrate‐N removal?
St. Joseph-Maumee
Cedar P t
TippecanoeUpper
SciotoUpper Miami
Portage
Two‐stage floodplains slow water velocities during storms
H d h600
Hydrograph
e (l
s-1 ) 400
500Direct RunoffBaseflow
Dis
char
ge
100
200
300
200• Agric lt ral streams ha e flash
1/1/2009 4/1/2009 7/1/2009 10/1/20090
n fr
eque
ncy
per y
ear)
100
150
200
KLA
BUL SHA
RID
2011 (wet)* r2=0.942012 (dry)* r2=0.91 p<0.05
• Agricultural streams have flashy discharge, especially during winter/spring
S fl i dIn
unda
tion
(day
s p
0
50
100CRE CRO
RAN
POW• Storm flows inundate two‐stage floodplains, but duration varies in wet and dry years.
Bench height (m)0.2 0.3 0.4 0.5
0• Net effect: decrease in water
velocities, and increased sedimentation. Tank, Mahl et al. unpublished data
Does the two stage influence sediment export? 500
• Two‐stage reduced water column turbidity, even as the two stage ages
Turbidity during2-stage inundation
ity (N
TU)
300
400
500Trapezoid2-Stage
the two stage ages.
• Turbidity correlates with
Turb
idi
0
100
200
* * *
* *
* *
*
6Ch li d
total phosphorus (TP), so reducing sediment load may reduce particle‐
Site (age in years)CRE(1) POW(2) RID(2) RAN(2) KLA(3) CRO(5) SHA(6) BUL(7) CEP(Nat.)
TP -
ug s-
1)
4
5ChannelizedTwo-stage
y passociated P export.
Take home: During inundation, the LO
G(T
1
2
3
POW
two-stage ditch slows water velocities, allowing sediments to deposit onto floodplains.
LOG(NTU)
-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.51
Q: Does this have benefits for phosphorus export?
Tank, Davis et al. unpublished data
• We are monitoring water
Does the two stage reduce particulate and dissolved P?
POW• We are monitoring water chemistry using paired sampling approach comparing two stage with upstream fe
renc
eL-1
)
0
200800Two-stage
POWRANRIDSHA
two‐stage with upstream channelized reach.
• TP was variable; at Shatto TP was generally lower in two‐
TP d
iff(u
g
-200 POWRANRIDSHA
Two-stagewas generally lower in two‐stage reach.
• Similar results for dissolved P; two‐stage also reduced 300
7/1/2010
1/1/2011
7/1/2011
1/1/2012
7/1/2012
1/1/2013
7/1/2013 -400
S
two stage also reduced concentrations but reduction depended on site (e.g., manure). 100
200
300
POWRANRIDSHA
eren
ceL-1
)
Two-stage Two-stage
manure).
Take-home: The two-stage can reduce TP and SRP export, but stream-specific landscape
-100
0
SR
P d
iffe
(ug
L
Two-stage
Two stagestream-specific landscape practices matter, and can mediate efficacy. 7/1/2010
1/1/2011
7/1/2011
1/1/2012
7/1/2012
1/1/2013
7/1/2013 -200
gTwo-stage
Tank, Davis et al. unpublished data
Quantifying N removal via denitrification
• Permanent Removal: denitrification– Microbial conversion of dissolved N to gaseous N– Microbial conversion of dissolved N to gaseous N
– Occurs in the presence of organic matter & anoxia
• Denitrification measurement– Transects: stream sediments &fl d l i il
.Lab assay bottles
floodplain soils– Lab assays: (acetylene reduction)
NO ‐
N2O/N2
Lab assay bottles
NO3
denitrificationOM
Do two‐stage floodplains increase denitrification N removal?
• During flooding, the two-stage 10000During flooding, the two stage significantly increased bioreactive surface area and thus reach-scale denitrification; rates
N reduction
l (g/
day)
wo-
stag
e
6000
8000Inset channelBench
4x
5x
7x
reach scale denitrification; rates were 4-24x higher than for channelized ditch alone.
N R
emov
alpe
r km
of t
w
2000
4000
15x
4x24x
• Denitrification N removal tended to increase as floodplains get older, and we found that older
CRE SHA KLA CRO BUL CEP0
(1 y) (3 y) (3 y) (5 y) (7 y) (Nat)
16,two-stages have richer floodplain soils, which provides C for denitrifying microbes.
Bench soil richness
nic
er (%
)8
12
16
y g
Take home: Two-stage floodplains “mature” through time, and
Org
anM
atte
0
4
8
denitrification nitrate-N removal improves without additional stream management
CRE SHA KLA CRO BUL CEP(1 y) (3 y) (3 y) (5 y) (7 y) (Nat)
Tank, Mahl et al. unpublished data
• Combining inundation data i h d i ifi i l
Can improved denitrification N removal reduce nitrate export?
14001600
mature sites* (r2=0.92, p=0.04)tl t t dwith denitrification N removal,
we can estimate annual N removal by floodplains.
-rem
oval
km
/yr)
800100012001400
SHA(3y)
BUL(7y) KLA(3y)
recently constructed
• Mature two‐stage: 300‐1100 kg N/km/yr, while younger two‐ A
nnua
l N-
(kg
N/k
200400600
BUL(7y)
CRO(5y)CEP(nat.) SHA(1y)
CRE(1y)
6000
stages remove less.
• No consistent declines in NO3‐
flood frequency (days per year)20 40 60 80 100 120 140 160 180
0
2000
0
2000
4000
diffe
renc
eL-1
)-2
2
4Two-stage Two-stage Two-stage Nitratedue to high concentrations (>5mg/L ); currently too high to be significantly reduced by
-8000
-6000
-4000
-2000
POWRANRIDSHA
NO
3- -N d
(ug
-1
-
-
-4
Two-stage Two-stage Two-stage
g y y600‐800m of two‐stage.
Take-home: Efficacy could be improved if two-stages were
7/1/2010
1/1/2011
7/1/2011
1/1/2012
7/1/2012
1/1/2013
7/1/2013 -10000
1p glonger or practice combined with other land management to reduce nutrient inputs. Tank, Mahl, Davis unpublished data
• Most NO3 enters streams
Reducing nutrient inputs into adjacent waterways
through tile drains during winter and spring when fields are bare.are bare.
• Cover crops, like ryegrass, can be planted after cash crop harvest; growth coincidesharvest; growth coincides with critical period for NO3 export (March‐May).
• Preliminary data suggest that cover crops have potential to significantly reduce NO3significantly reduce NO3 export from tile drains.
Take-home: Stacking management ti lik ith ipractices like cover crops with in-
stream practices like the two-stage could further improve water quality.
Tank & Hanrahan unpublished data
• With two‐stage, tile drains empty onto floodplain
Can two‐stage floodplains reduce nitrate during baseflow?
benches.• During base‐flow, two‐stage can reduce NO3
‐nitrate from tiles depending upon length of flow path.
r2=0.89, p < 0.0001
mov
al
30405060
% N
Rem
0102030
Tracer addition shows flow path from tile drain
Flow path length (m)0 5 10 15 20 25 30
T k h R t ti f tilTake-home: Retention of tile drainage water on floodplains improves N removal.
Tank & Davis unpublished data
Summary: effects of two‐stage ditch on water quality
• During storms, the two‐stage can reduce sediments and increase nutrient removal via floodplain inundation, which can be extensive depending on water year and height of floodplain construction.p g y g p
• With no additional maintenance ,the two‐stage practice “ages” well and function improves, making it a self‐sustaining practice.
• During baseflow, two‐stage floodplains can also reduce NO3‐ in tile
water as the flowpath moves across vegetated floodplains.
• Stacking the two‐stage with other landscape practices (e g cover• Stacking the two‐stage with other landscape practices (e.g., cover crops) may be even more effective in managing nutrient export in a high‐nutrient landscape.
Roley, S. S., J.L. Tank, M.L. Stephen, L.T. Johnson, J.J. Beaulieu and J.D, Witter. 2012. Floodplain restoration enhances denitrification and reach-scale nitrogen removal in an agricultural stream. Ecological Applications. 22: 281–297.
Roley, S. S., J.L. Tank, and M.A. Williams. 2012. Hydrologic connectivity increases denitrification in the hyporheic zone and restored floodplains of an agricultural stream. J. Geophys. Res- Biogeosciences. doi:10.1029/2012JG001950
Implementation best practices –th t t dit h k b t hthe two‐stage ditch works best when:
• Floodplain benches are inundated regularly.p g y
best when > 12 inundation events per year.• Tile water flows across floodplains for as long as possible.Tile water flows across floodplains for as long as possible.
Construct tile outlets so not rip‐rapped.• Floodplain benches “age” better when vegetatedFloodplain benches age better when vegetated.
Species identity secondary, does not alter N removal.
Take‐home: The two‐stage is a potential tool in the nutrient management toolbox that can be implemented to improvemanagement toolbox that can be implemented to improve water quality while coexisting with productive agriculture.
Two‐stage Information:Nutrient and sediment benefits (Univ of Notre Dame)Nutrient and sediment benefits (Univ. of Notre Dame)
Jennifer Tank [email protected]
Site Evaluation and channel stability (The Ohio State Univ.)Site Evaluation and channel stability (The Ohio State Univ.)
Andy Ward [email protected]
Jon Witter [email protected]
Implementation & outreach (Indiana Nature Conservancy)
Kent Wamsley [email protected]
Carrie Vollmer‐Sanders [email protected]
Thanks to our partners and funding sources:Thanks to our partners and funding sources:
