examining higher hydraulic gradients in restored streams ... · overview of presentation •...
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Examining Higher Hydraulic Examining Higher Hydraulic Gradients in Restored Streams and
the Implications on Hyporheic ExchangeExchange
Hong-Hanh Chu and Dr. Ted Endreny,g 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 Exchange Overviewyp g• Boulton et. al., 1998 :▫ Hyporheic Zone: an “active ecotone between the yp
surface stream water and groundwater”▫ Hyporheic Exchange: the “exchanges of water,
nutrients, and organic matter occur [in the hyporheic , g ypzone] in response to variations in discharge and bed topography and porosity” hydraulic head
Lateral
Vertical hyporheic exchange
Figure from Hester and Gooseff, 2010
Lateral hyporheic exchange
g
Hyporheic Exchange Overviewyp gFunctions commonly associated with:
Lateral hyporheic exchangeVertical hyporheic exchange
• Lotic habitat▫ Invertebrates & macroinvertebrates
Fi h
• Nutrient cycling▫ Consumption & transformation by
microbes
Lateral hyporheic exchangeVertical hyporheic exchange
▫ Fish
• Nutrient cycling▫ Consumption & transformation by microbes
▫ Oxygen and energy cycling
microbes
▫ Oxygen and energy cycling
• Pollutant buffering▫ Sink for hard metals and hydrocarbons yg gy 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
Stream Restoration Research• Vertical hyporheic exchange:▫ Hydraulics:Hydraulics:
Crispell and Endreny, 2009: Batavia Kill, NYHester and Doyle, 2008: simulation models, flume tests, field experiments in Craig Creek (small mountain stream) field experiments in Craig Creek (small mountain stream) near Blacksburg, VA
▫ Biogeochemistry:Lautz and Fanelli 2008: 3rd order Red Canyon Creek in Lautz and Fanelli, 2008: 3 order Red Canyon Creek in Lander, WY (semi-arid watershed)
• Lateral hyporheic exchange:▫ Hydraulics and Biogeochemistry:▫ Hydraulics and Biogeochemistry:
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 ffaffect:
- the hydraulic gradients in the stream channel and across the stream meander bend andacross the stream meander bend, and
- the intra-meander water table level?
Use methodologies that will provide:1) direct comparisons between channels with structures and channels
ith t t t dwithout structures, and2) fine resolution of observation data at the scale of a stream meander.
Methods: Laboratory ExperimentsStream Channel Dimensions:
- Width to Depth ratio: 7 to 11
- Sinuosity: 1.9 Radius of Curvature: 26 cmy
- Channel slope: 1% Valley slope: 1.5%
- D50: 0.2 mm nno struct = 0.004 nstruct = 0.021
- Initial channel: flat bed morphology
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:
di i l d f- 2 NIKON D5100 digital cameras mounted 1.3 m from sand surface
- Digital photos taken of initial channel, river stage at 7 hrof flow, and channel after 12+ hr of no flow
22%20%10-11%
14%
- 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)
22%
20%
Methods: Post-Processing
Import DEMs in ArcGIS
Using ADAM Tech 3DM Analyst: Using ESRI ArcGIS:
Convert TINs into Rasters
Convert DEMs into TINs
Obtain cross-section profiles with 3D Analyst extension
E t ti fil d t i t E l f
- Hydraulic gradients
Analysis of variance on:
Export cross-section profile data into Excel for calculations
(Diagram courtesy of Bangshuai Han)
Hydraulic gradients- Water table levels
8506-29 structures
7-2 structures
Longitudinal Profile of River Stage at the Channel Centerline
830
840
m)
7-3 structures
7-4 structures
7-7 no structures
7-8 no structures
7-9 no structures
810
820
Ele
va
tio
n (
mm
channel flat bed (7-7)
6.7 mm (avg) 8.6 mm (avg) 3.0 mm (avg)
Hydraulic radius (R) increased 80% of the
Hydraulic radius (R) increased 22% of
800
E
N N’
original R. original R.
N’
NHaving structures in the channel, especially the cross-vane, raised the river stage that is upstream of the structures.
- Backwater from damming effect
850
Hydraulic Gradient between US and DS River Stage
840
Having structures in the channel raised the river stage hydraulic gradient across the meander:
neck by 0 94%
830
mm
)
- neck by 0.94%
- center by 1.39%
- apex by 0.12%
820
Ele
va
tio
n (
m
Neck w/o structures
Neck with structures
The river stage hydraulic gradients of channels with structures and those of channels without structures
810
Neck with structures
Center w/o structures
Center with structures
Apex w/o structures
those of channels without structures are statistically different (p=0.0002).
800
Apex w/o structures
Apex with structures
ne
c
cen
t
ap
eUS river stage DS river stage ckter
ex
The structures affected the hydraulic gradient across the meander locations disproportionately (p<0.0001).
g g
Intra-Meander Cross-Sections
Having structures in the channel increased the water table throughout the
840
850
860
870
on
(m
m)
6-29 Structures7-2 Structures7 3 Structures
neck
g gintra-meander zone, especially in the upstream half of the bend.
870810
820
830
840
Ele
va
tio 7-3 Structures
7-4 Structures7-7 No structures7-8 No structures7-9 No structures
US channelriver stage
DS channel river stage
well water
well waterwell water
Astruct: 6.26%Ano struct: 3.74% Bstruct: 4.01%
Bno struct: 3.39% Cstruct: 2.24%C 2 03%
840
850
860
7
tio
n (
mm
)
centerThe steepest hydraulic gradient increase from in-channel structures
Cno struct: 2.03%Dstruct: 1.49%Dno struct: 0.87%
810
820
830
Ele
va
t
DS channel river stage
US channelriver stage well water
well water
well water
870
occurred at the meander center, immediately upstream of cross-vane.
Astruct: 5.86%Ano struct: 1.70%
Bstruct: 4.65%Bno struct: 3.34% Cstruct: 3.80%
Cno struct: 2.97% Dstruct: 1.44% %
840
850
860
ion
s (m
m)
apex
ne
c
cen
t
ap
e
Dno struct: 1.79%
Cstruct: 1.82%Cno struct: 2.07%
Dstruct: 1.37%Dno struct: 2.31%
810
820
830
Ele
va
ti
DS channel river stage
US channelriver stage
well waterwell water
well water
ckter
ex
Astruct: 2.24%Ano struct: 0.17%
Bstruct: 2.10%Bno struct: 2.44%
830.00
m)
Wells at meander center
835.00
Wells near structures
824.00
826.00
828.00
wa
ter
lev
el
(mm
0.97
1.74
829 00
831.00
833.00
er
lev
el
(mm
)
820.00
822.00
824.00
Av
g.
we
ll w
apex center neck
1.08 0.44 1.27
2.53 3.70 3.14
2.46 2.14 1.870.83
825.00
827.00
829.00
Av
g.
we
ll w
at
apex center neck
Structures No Structures
p
The water level of the circled wells was statistically different:- between channels with structures and those without structures ( ) d
The water level of these wells was: - marginally different between channels with structures and h i h ( ) d
Structures No Structures
(p=0.0057), and - across meander locations (neck, center, apex) (p<0.0001).
those without structures (p=0.0797), and- 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 Stageduring twice normal discharge
850
When discharge was doubled in channels with structures:840
850
channels with structures:
- river stage increased with similar magnitude throughout the channel, and 830
4
mm
)
- hydraulic gradients across the meander bend remained relatively unchanged.
820
Ele
va
tio
n (
m
Neck @ 2x normal Q
Center @ 2x normal Q
810
Apex @ 2x normal Q
Neck @ normal Q
Center @ normal Q
ne
c
cen
t
ap
eUS river stage DS river stage800
Center @ normal Q
Apex @ normal Q
ckter
exg g
Normal Q = 51 ml/s
Result Summaryy
• In-stream restoration structures can locally raise the river stage 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 i f i t d h d li di t d t • The increase of intra-meander hydraulic gradients and water 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 to further increase hydraulic pp ygradients under higher stream flow.
Implications on Hyporheic Exchange
• Steep hydraulic gradients in riparian areas closest to the structures could indicate areas of closest to the structures could indicate areas of induced lateral hyporheic exchange. ▫ Potential biogeochemical hotspots in the intra-Potential biogeochemical hotspots in the intra
meander 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 More laboratory experiments to obtain observation data on hyporheic exchange flux and pathways in the stream channel and intra-meander zone.
R n e periments at different stream discharges and channel ▫ Run experiments at different stream discharges and channel restoration designs.
• MODFLOW modeling to simulate and predict hyporheic h fl d hexchange flux and pathways.
▫ DEMs generated by our research process can provide fine resolution observation data of ground and water surfaces as MODFLOW boundary conditions.
Questions?References: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 Ontario, Canada, Journal of the American Water Resources, So O o, C , Jo of so sAssociation (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
d lli ( ) l bi h i l h i h b d d iLautz, L.K. and R.M. Fanelli, (2008), Seasonal biogeochemical hotspots in the streambed around restoration structures, Biogeochemistry, 91, 85-104.