examining higher hydraulic gradients in restored streams ... · overview of presentation •...

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.