Monitoring of Groundwater-Surface Water Interactions in Support of Restoration of Hyporheic Processes in an Urban Stream, Thornton Creek, Washington

GSA 2009 Annual Meeting, Portland, Oregon, Session No. 177, October 20, 2009

Paul D. Bakke1, Katherine Lynch2, Tracy Leavy1 and Roger Peters1

1Washington Fish & Wildlife Office, U.S. Fish & Wildlife Service, 510 Desmond Drive SE, Suite 102, Lacey, WA 98503

2Seattle Public Utilities, 700 5th Ave., Suite 4400, P.O. Box 34018, Seattle, WA 98124

THE CHALLENGE OF RESTORING URBAN STREAMS:

•At least three forms of degradation are present: high stormwater runoff rates, loss of habitat structure, & degraded water quality

•Restoration of water quality is poorly documented

•Many confounding influences

•Expensive real estate and limited available space for projects

PURPOSE OF THIS STUDY:

•Demonstrate methodology for monitoring restoration of hyporheic processes

•Conduct pre-project monitoring to establish baseline conditions & inform restoration design

METHODS:

•Stream-segment scale (hydro-geomorphic context):

•Piezometer approximately 1.4 meters into streambed, measures:

•piezometric head

•streambed temperature at 3 elevations

•VS2DHI Hydraulic-thermal model calibration to estimate

•Hydraulic conductivity of streambed

•Groundwater influx rate

•Heat flux into/out of streambed

METHODS:

•Habitat-unit scale (local hyporheic interchange)

•Extensive streambed temperature measurements during one day, late summer base flow season

•Array of 50 – 60 tubes, 10 cm into gravel. Temperature in each tube measured 3 times.

•Compare intra-gravel temperature (bottom of tube) with surface water temperature to map zones of upwelling & downwelling, & relative strength

THORNTON CREEK WATERSHED CHARACTERISTICS:

•Watershed area: Total 28.4 sq. km (11.0 sq. mi.)

North Fork 16.7 sq. km (6.5 sq. mi.)

South Fork 9.1 sq. km (3.5 sq. mi.)

•Current (1999 - 2008) mean annual flow: 0.261 m3/s (261 L/s or 9.2 CFS)

•Human population: 75,400 (estimated)

•Proportion of watershed with impervious surfaces: 49 percent

Concept No. 1: Alluvial fan - Step-pool channel (Rosgen A or G) with hyporheic streambed

Advantages:

•Fits well into small available area

•Passes bedload sediment well

•Streambed scour could prevent clogging by fines

Disadvantages:

•Hyporheos confined to channel footprint

•Little active floodplain function or floodplain hyporheic component

•Difficult to prevent hyporheic water from being lost to water table without greatly restricting extent of subsurface flow

•Streambed scour potential high

Concept No. 3: Depositional forested wetland complex with complex subsurface interactions

Advantages:

•Fits well into small available area

•Consistent with historic habitat conditions at site

•Wetland function creates nutrient sink for water quality improvement, especially if inundation is seasonal, with vertical movement of anaerobic zone

•Habitat for wetland species, including beaver

Disadvantages:

•Does not pass sediment = long term aggradation likely without active sediment removal

• Sluggish wetland flow & low hydraulic conductivity reduces hyporheic exchange, with loss of cooling potential

RESTORATION OF HYPORHEIC PROCESSES at Forks Confluence site: Goals -

•Sustainable water quality improvement (cooling, nutrient reduction)

•Increased intra-gravel flow for improved spawning habitat

WesternWashington

LakeWashington

Seattle

Thornton Cr. Watershed

95th Street

N.F. Confluence

S.F. Confluence

Knickerbocker

Control Reach Treatment Reach

8 cm

1.4

to 1

.5 m

Streambed

Water

Locking Cap

3.8

cm d

iam

. st

eel p

ipe

3 mm holes South Fork

Main Stem

North Fork

North Fork

North Fork

South Fork

1.

2.

5.

Concept No. 2: Depositional response reach with single-thread channel (Rosgen C or Bc) plus side channels, floodplain hyporheic pathways

Advantages:

•Active floodplain with side channels

•Subsurface preferential flow pathways = extensive hyporheos with diverse water residence time

•Soil water & sediment recharge during moderate floods

•Traps fine sediment on floodplain

•More stable fish habitat (less scour, deeper alluvium)

Disadvantages:

•Difficult to fit into available area

• May aggrade without active sediment removal if sediment sources not controlled

Intra-Gravel Temperature Differences

Site

KNK-C KNK-T 95th-C 95th-T SFC-C SFC-T NFC-C NFC-T

Su

rfac

e T

emp

- S

ubs

urf

ace

Tem

p, C

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

RESULTS: Shown for each site -

•Streambed vertical thermal profile for typical late-summer period, 48 hours long

•Plan view map of reach with surface-subsurface temperature difference isotherms, showing relative downwelling/upwelling

•Average piezometric gradient

•Groundwater influx rate & total reach-scale groundwater input to compare with surface water discharge

•Crossover dates: the time when the vertical thermal gradient in the streambed changes from positive (streambed cools the surface water) to negative (streambed warms the surface water)

•Estimated heat flux (cooling or warming) by streambed, with estimated cooling load in oC

Map

North Fork (Confluence) Control SiteHydraulic Conductivity 1.00E-06 m/sPiezometric gradient 0.1603 m/m

Groundwater influx rate 1.3E-07 m3/s/m2

Total reach groundwater input 2.8E-05 m3/s

Surface water discharge (estimated) 0.045 m3/s

Estimated heat flux to streambed 9.6 J/s/m2

Estimated surface water cooling from streambed -0.011 oCAutumn reversal of thermal gradient: Completion date 19-Sep-07

Duration 23 days

Knickerbocker Control SiteHydraulic Conductivity 1.00E-07 m/sPiezometric gradient 0.324 m/m

Groundwater influx rate 2.7E-08 m3/s/m2

Total reach groundwater input 7.0E-06 m3/s

Surface water discharge (estimated) 0.020 m3/s

Estimated heat flux to streambed 10.3 J/s/m2

Estimated surface water cooling from streambed -0.033 oCAutumn reversal of thermal gradient: Completion date 1-Oct-06

Duration 40 days

95th Street Treatment SiteHydraulic Conductivity 1.40E-06 m/sPiezometric gradient 0.0732 m/m

Groundwater influx rate 8.7E-08 m3/s/m2

Total reach groundwater input 3.2E-05 m3/s

Surface water discharge (estimated) 0.088 m3/s

Estimated heat flux to streambed 11.4 J/s/m2

Estimated surface water cooling from streambed -0.011 oCAutumn reversal of thermal gradient: Completion date 30-Sep-06

Duration 16 days

95th Street Control SiteHydraulic Conductivity 3.00E-07 m/sPiezometric gradient 0.399 m/m

Groundwater influx rate 1.1E-07 m3/s/m2

Total reach groundwater input 3.6E-05 m3/s

Surface water discharge (estimated) 0.082 m3/s

Estimated heat flux to streambed 7.7 J/s/m2

Estimated surface water cooling from streambed -0.008 oCAutumn reversal of thermal gradient: Completion date 1-Oct-06

Duration 40 days

North Fork Control, 09/11/07

TIME, HOURS

0 12 24 36 48

DE

PT

H,

M

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

14.0

14.5 15.0 15.5 16.0 16.0 16.5

Forks Confluence Treatment, 09/11/07

TIME, HOURS

0 12 24 36 48

DE

PT

H,

M-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

14.0

14.5 15.0 15.5 16.0 16.0 16.5

Knickerbocker Treatment, 09/04/06

TIME, HOURS

0 12 24 36 48

DE

PT

H,

M

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

13.5 14.0 14.5 15.0 15.5 16.0 16.5

Knickerbocker Control, 09/04/06

TIME, HOURS

0 12 24 36 48

DE

PT

H,

M

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

13.5 14.0 14.5 15.0 15.5

16.0 16.5

95th Street Treatment, 09/06/06

TIME, HOURS

0 12 24 36 48

DE

PT

H,

M

-1.4

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

14.0 14.5 15.0 15.5 16.0 16.5

95th Street Control, 09/06/06

TIME, HOURS

0 12 24 36 48

DE

PT

H,

M

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

14.5 15.0 15.5 16.0 16.5

Lake Washington

South Fork (Confluence) Control SiteHydraulic Conductivity 1.00E-05 m/sPiezometric gradient -0.0233 m/m

Groundwater influx rate -2.1E-07 m3/s/m2

Total reach groundwater input -3.5E-05 m3/s

Surface water discharge (estimated) 0.042 m3/s

Estimated heat flux to streambed 13.3 J/s/m2

Estimated surface water cooling from streambed -0.013 oCAutumn reversal of thermal gradient: Completion date 19-Sep-07

Duration 24 days

S Fork Control, 09/11/07

TIME, HOURS

0 12 24 36 48

DE

PT

H,

M

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

13.5 14.0 14.5 15.0 15.5 16.0 16.5

Forks Confluence Treatment SiteHydraulic Conductivity 2.00E-05 m/sPiezometric gradient 0.0033 m/m

Groundwater influx rate 4.7E-08 m3/s/m2

Total reach groundwater input 7.5E-06 m3/s

Surface water discharge (estimated) 0.094 m3/s

Estimated heat flux to streambed 13.1 J/s/m2

Estimated surface water cooling from streambed -0.0053 oCAutumn reversal of thermal gradient: Completion date 19-Sep-07

Duration 24 days

To 95th S

treet

Treatm

ent Reach

From

Forks

Confluence

Reach

To Lake Washington

Knickerbocker Treatment SiteHydraulic Conductivity 1.00E-06 m/sPiezometric gradient 0.261 m/m

Groundwater influx rate 2.2E-07 m3/s/m2

Total reach groundwater input 2.8E-05 m3/s

Surface water discharge (estimated) 0.020 m3/s

Estimated heat flux to streambed 10.9 J/s/m2

Estimated surface water cooling from streambed -0.017 oCAutumn reversal of thermal gradient: Completion date 28-Oct-06

Duration 67 days

CONCLUSIONS:

•Hydraulic conductivities at all sites, even those with alluvial subsurface, is very low

•Consequently, vertical groundwater input rate is very low at all sites, even though piezometric gradient is large

•Heat exchange with streambed is currently conduction dominated, so cooling load is low

•Subtle hyporheic exchange is evident, but extremely slow due to impermeable sediments

Subsurface warmer than surface at two sites (KNK-T, KNK-C, in figure above), indicating substantial lack of advection flow

Lateral groundwater input evident at 2 sites (KNK-T, SFC-C, in figure above)

•Crossover dates and duration vary widely by site. Inter-annual variability also can be large.

2006, 2007 & 2008 Autumn Crossover

27-Jul

6-Aug

16-Aug

26-Aug

5-Sep

15-Sep

25-Sep

5-Oct

15-Oct

95th-T NFC-C SFC/NFC-T SFC-C

Site

Dat

e

2007 Begin

2007 Complete

2008 Begin

2008 Complete

2006 Begin

2006 Complete

Streambed: gravel surface over sand & gravel alluvium

Streambed: gravel surface over sand & gravel alluvium

Streambed: veneer of alluvial gravel over massive clay

Streambed: veneer of alluvial gravel over massive clay

Streambed: veneer of alluvial gravel over massive pebbly clay

Streambed: gravel surface over sand & gravel alluvium

Streambed: gravel surface over sand & gravel alluvium

3.

4.Distribution of temperature differences at each site during one-day extensive study.

Crossover period - the time during which the vertical thermal gradient in the streambed changes from positive (streambed cools the surface water) to negative (streambed warms the surface water)

References:

Conant, B., Jr. 2004. Delineating and quantifying groundwater discharge zones using streambed temperatures. Ground Water, 42(2):243-257.

Hsieh, P. A., W. L. Wingle, and R. W. Healy, 2000. VS2DI—A Graphical Software Package for Simulating Fluid Flow and Solute or Energy Transport in Variably Saturated Porous Media. USGS Water-Resources Investigations Report 99-4130. 16 pp.

Stonestrom, D.A., and Constantz, J., eds., Heat as a tool for studying the movement of ground water near streams: USGS Circular 1260. 96 pp.