Examining Higher Hydraulic
Gradients in Restored Streams and
the Implications on Hyporheic
Exchange
Hong-Hanh
g
Chu and Dr. Ted Endreny,
y,
Department of Environmental Resources Engineering, SUNY ESF
Overview of Presentation
• Hyporheic exchange
• Studies on stream restoration, especially about
hydraulic gradients and river stage
• Our research
• Future research and implications on hyporheic
exchange
Hyporheic
yp
Exchange
g Overview
• Boulton et. al., 1998 :
▫ Hyporheic
yp
Zone: an “active ecotone between the
surface stream water and groundwater”
▫ Hyporheic Exchange: the “exchanges of water,
nutrients,, and organic
g
matter occur [in the hyporheic
yp
zone] in response to variations in discharge and bed
topography and porosity”
hydraulic head
Lateral
hyporheic
exchange
Vertical
hyporheic
exchange
g
Figure from Hester and Gooseff, 2010
Hyporheic
yp
Exchange
g Overview
Functions commonly associated with:
Vertical hyporheic exchange
• Lotic habitat
▫
▫
Invertebrates & macroinvertebrates
Fi h
Fish
• Nutrient cycling
▫
▫
Consumption & transformation by microbes
Oxygen
yg and energy
gy cycling
y
g
• Pollutant buffering
▫
Sink for hard metals and hydrocarbons
• Temperature regulation
▫
▫
▫
Surface water vs. groundwater
Habitat quality, especially during low flow
Constraint on biogeochemical reactions
Lateral hyporheic exchange
• Nutrient cycling
▫
▫
Consumption & transformation by
microbes
Oxygen and energy cycling
• Pollutant buffering
▫
Sink for hard metals and hydrocarbons
Stream Restoration Research
• Vertical hyporheic exchange:
▫ Hydraulics:
x Crispell and Endreny, 2009: Batavia Kill, NY
x Hester and Doyle, 2008: simulation models, flume tests,
field experiments in Craig Creek (small mountain stream)
near Blacksburg, VA
▫ Biogeochemistry:
x Lautz and Fanelli,
Fanelli 2008: 3rd order Red Canyon Creek in
Lander, WY (semi-arid watershed)
• Lateral hyporheic exchange:
▫ Hydraulics and Biogeochemistry:
x Kasahara and Hill, 2007: 2 lowland stream reaches of
Boyne River, Ontario, CA (intensive agri. watershed)
Science Question
How do in-channel stream restoration structures
affect:
ff
- the hydraulic gradients in the stream channel and
across the stream meander bend,
bend and
- the intra-meander water table level?
Use methodologies that will provide:
1) direct comparisons between channels with structures and channels
without
ith t structures,
t t
and
d
2) fine resolution of observation data at the scale of a stream meander.
Methods: Laboratory Experiments
Stream Channel Dimensions:
-
Width to Depth ratio: 7 to 11
-
Sinuosity:
y 1.9
-
Channel slope: 1%
-
D50: 0.2 mm
-
Initial channel: flat bed morphology
Radius of Curvature: 26 cm
Valley slope: 1.5%
nno struct = 0.004
nstruct = 0.021
Experimental Runs:
-
Discharge: 51 ml/s (~30% of channel capacity)
-
Flow Duration: 7 hr
-
3 replications of channel without structures
-
4 replications of channel with 6 J-hooks and 1 cross-vane
Close-Range Photogrammetry:
14%
10-11%
20%
20%
22%
-
2 NIKON D5100 digital
di i l cameras mounted
d 1.3 m ffrom
sand surface
-
Digital photos taken of initial channel, river stage at 7 hr
of flow, and channel after 12+ hr of no flow
-
Floating white wax powder (0.3 mm diameter) indicated
river stage and well water level
-
Elevation values referenced to 5 control points surveyed
by ultrasonic distance sensors (0.2 mm precision)
Methods: Post-Processing
Using ADAM Tech 3DM Analyst:
Using ESRI ArcGIS:
Import DEMs in ArcGIS
Convert DEMs into TINs
Convert TINs into Rasters
Obtain cross-section profiles with 3D Analyst
extension
E
Export
t cross-section
ti profile
fil data
d t into
i t Excel
E l ffor
calculations
Analysis of variance on:
(Diagram courtesy of Bangshuai Han)
- Hydraulic gradients
- Water table levels
Longitudinal Profile of River Stage at the Channel Centerline
850
6-29 structures
7-2 structures
7-3 structures
7-4 structures
7-7 no structures
7-8 no structures
7-9 no structures
channel flat bed (7-7)
840
Elevation (mm
E
m)
830
820
6.7 mm (avg)
Hydraulic radius (R)
increased 80% of the
original R.
810
800
8.6 mm (avg)
3.0 mm (avg)
Hydraulic radius (R)
increased 22% of
original R.
N
N’
N’
Having structures in the channel, especially the cross-vane, raised the river
stage that is upstream of the structures.
- Backwater from damming effect
N
Hydraulic Gradient between US and DS River Stage
850
Having structures in the channel raised the
river stage hydraulic gradient across the
meander:
840
- neck by 0.94%
0 94%
Elevation (m
mm)
- center by 1.39%
- apex by 0.12%
830
820
The river stage hydraulic gradients
of channels with structures and
those of channels without structures
are statistically different
(p=0.0002).
Neck w/o structures
Neck with structures
Center w/o structures
810
Center with structures
Apex w/o structures
Apex with structures
The structures affected the hydraulic gradient across the
meander locations disproportionately (p<0.0001).
nec
ck
DS river stage
g
centter
US river stage
g
ape
ex
800
Intra-Meander Cross-Sections
Elevatio
on (mm)
870
neck
860
850
830
820
860
US channel
river stage
well water
Astruct: 6.26%
Ano struct: 3.74%
Bstruct: 4.01% well water
well water
Cstruct: 2.24%
Bno struct: 3.39%
Cno struct: 2.03%
2 03%
center
DS channel
river stage
Dstruct: 1.49%
Dno struct: 0.87%
850
840
830
US channel
river stage
820
860
well water
well water
Astruct: 5.86%
: 4.65%
B
Ano struct: 1.70% struct
Bno struct: 3.34%
810
870
apex
840
830
820
810
US channel
river stage
well water
Astruct: 2.24%
Ano struct: 0.17%
well water
Bstruct: 2.10%
Bno struct: 2.44%
Dstruct: 1.44%
Dno struct: 1.79%
%
Dstruct: 1.37%
Dno struct: 2.31%
well water
DS channel river stage
nec
ck
Cstruct: 1.82%
Cno struct: 2.07%
DS channel river stage
centter
850
well water
Cstruct: 3.80%
Cno struct: 2.97%
The steepest hydraulic
gradient increase from inchannel structures
occurred at the meander
center, immediately
upstream of cross-vane.
ape
ex
Elevatiions (mm)
6-29 Structures
7-2 Structures
7 3 Structures
7-3
7-4 Structures
7-7 No structures
7-8 No structures
7-9 No structures
840
810
870
7
Elevattion (mm)
Having
g structures in the channel increased the water table throughout
g
the
intra-meander zone, especially in the upstream half of the bend.
Wells at meander center
Wells near structures
Avg. well water level (mm)
835.00
833.00
831.00
829 00
829.00
2.53
3.70
3.14
827.00
1.08
825.00
0.44
1.27
2.46
center
apex
Structures
2.14
1.87
neck
No Structures
Avg. well w
water level (mm
m)
830.00
828.00
0.97
1.74
826.00
824.00
822.00
0.83
820.00
apex
p
Structures
center
neck
No Structures
The water level of the circled wells was statistically different:
- between channels with structures and those without structures
(
(p=0.0057),
) and
d
- across meander locations (neck, center, apex) (p<0.0001).
The water level of these wells was:
- marginally different between channels with structures and
those
h
without
ih
structures ((p=0.0797),
) and
d
- statistically different across meander locations (p<0.0001).
The structures impacted these wells’ water level
disproportionately across meander locations (p=0.0001)
The structures did NOT impact these well water levels
disproportionately across meander locations (p=0.2889).
Hydraulic Gradient between US and DS River Stage
during twice normal discharge
850
When discharge was doubled in
channels with structures:
Elevation (m
mm)
840
4
-
river stage increased with similar
magnitude throughout the
channel, and
-
hydraulic gradients across the
meander bend remained
relatively unchanged.
830
Neck @ 2x normal Q
820
Center @ 2x normal Q
Apex @ 2x normal Q
Neck @ normal Q
810
Center @ normal Q
Apex @ normal Q
Normal Q = 51 ml/s
nec
ck
DS river stage
g
centter
US river stage
g
ape
ex
800
Result Summaryy
• In-stream
In stream restoration structures can locally raise the river stage
upstream of where they are installed.
▫ Cross-vanes can cause more backwater than J-hooks.
• Th
The increase
i
off intra-meander
i t
d hydraulic
h d li gradients
di t and
d water
t
table levels by in-channel stream restoration structures is most
pronounced at the intra-meander areas closest to the structures.
▫ There is marginal water table level increase in the middle of the
meander bend.
• The structures do not appear
pp
to further increase hydraulic
y
gradients under higher stream flow.
Implications on Hyporheic Exchange
• Steep hydraulic gradients in riparian areas
closest to the structures could indicate areas of
induced lateral hyporheic exchange.
▫ Potential biogeochemical hotspots in the intra
intrameander zones.
• Larger stream flow in channels with restoration
structures could induce more vertical hyporheic
exchange due to higher hydraulic head.
Future Research
• More laboratory experiments to obtain observation data on
hyporheic exchange flux and pathways in the stream channel
and intra-meander zone.
▫ R
Run
n experiments
e periments at different stream discharges and channel
restoration designs.
• MODFLOW modeling to simulate and predict hyporheic
exchange
h
flux
fl and
d pathways.
h
▫ DEMs generated by our research process can provide fine
resolution observation data of ground and water surfaces as
MODFLOW boundary conditions.
Questions?
References:
Boulton, A.J., Findlay, S., Marmonier, P., Stanley, E.H., and Valett, H.M. (1998), The functional significance of
the hyporheic zone in streams and rivers, Annu. Rev. Ecol. Syst., 29, 59-81.
Crispell, J.K. and T.A. Endreny (2009), Hyporheic exchange flow around constructed in-channel structures and
implications for restoration design, Hydrol. Process., 23-1158-1168.
Hester, E.T. and M.W. Doyle (2008), In-stream geomorphic structures as drivers of hyporheic exchange, Water
Resour. Res., 44, W03417, doi:10.1029/2006WR005810.
Hester, E.T. and M.N. Gooseff (2010), Moving beyond the banks: Hyporheic Restoration is Fundamental to
Restoring Ecological Services and Functions of Streams, Environ. Sci. Technol., 44, 1521-1525.
Kasahara, T. and A.R. Hill (2007), Lateral hyporheic zone chemistry in an artificially constructed gravel bar and
re-meandered stream channel,, Southern
So
Ontario,
O
o, Canada,
C
, Jo
Journal of the American Water Resources
so
s
Association (JAWRA) 43(5):1257-1269. DOI: 10.1111 / j.1752-1688.2007.00108.x.
Kasahara, T. and A.R. Hill (2007), In-stream restoration: its effects on lateral stream-subsurface water
exchange in urban and agricultural streams in Southern Canada, River Res. Applic., 23, 801-814
Lautz, L.K. and
d R.M. Fanelli,
lli (2008),
(
) Seasonall bi
biogeochemical
h i lh
hotspots iin the
h streambed
b d around
d restoration
i
structures, Biogeochemistry, 91, 85-104.