DOC and THMP loads from a restored wetland in the Delta DWR RD1601 CALFED CBDA staff USGS staff Jacob A Fleck Steven J. Deverel Roger Fujii.

DOCDOC and THMP loads from a and THMP loads from a restored wetland in the Deltarestored wetland in the Delta

DWR RD1601 CALFED CBDA staff USGS staff

Jacob A FleckJacob A Fleck

Steven J. DeverelSteven J. Deverel

Roger FujiiRoger Fujii

Wetland restorationWetland restoration Many thousands acres of wetland Many thousands acres of wetland

restoration restoration All native wetland types: Tidal, non-tidal, mudflatAll native wetland types: Tidal, non-tidal, mudflat BenefitsBenefits

Provide habitat for native species Provide habitat for native species Improve ecosystem function Improve ecosystem function Flood protectionFlood protection Subsidence mitigation on organic soilsSubsidence mitigation on organic soils

Engineering difficulties (deep subsidence)Engineering difficulties (deep subsidence) Island in-fillIsland in-fill Setback leveesSetback levees Impounded, flow-through wetlandsImpounded, flow-through wetlands

USGS/DWR wetland restoration USGS/DWR wetland restoration demonstration projectdemonstration project

Initially established in 1997 Initially established in 1997 Use of wetland restoration as Use of wetland restoration as

subsidence mitigation technique on subsidence mitigation technique on deeply subsided islands deeply subsided islands

Impounded, flow-through systemImpounded, flow-through system This study established in 2000 This study established in 2000

To determine the effects that wetland To determine the effects that wetland restoration will have on DOC and THMP restoration will have on DOC and THMP loads from subsided peat islands.loads from subsided peat islands.

Demo pond setting: Demo pond setting: Twitchell IslandTwitchell Island

Twitchell IslandTwitchell Island

Deeply subsided Deeply subsided As much as 20 ft As much as 20 ft

Peat soils dominatePeat soils dominate >10 ft remain>10 ft remain ~35% OM~35% OM

Primarily Primarily agricultureagriculture srsr cornsrsr corn

Water upwellingWater upwelling

Twitchell Island drainageTwitchell Island drainage

Demonstration pondDemonstration pond ?

Soils/drainageSoils/drainage Peat soil high in CPeat soil high in C Two layersTwo layers

Zone of drain Zone of drain influenceinfluence

Well-decomposed Well-decomposed peatpeat

High hydraulic High hydraulic conductivityconductivity

Deep peatDeep peat Unaltered peat Unaltered peat Low hydraulic Low hydraulic

conductivityconductivity

Twitchell pumping stationTwitchell pumping station

WQ Effects?WQ Effects?

HCX3

OH

X

OHOOC O

HCCl2 Cl

Trihalomethanes

Haloacetic Acids

MX

Halophenols

CCXn

O=

OH

CCXn

O=

CR3

Haloketones

Haloacetonitriles

O

OH

H3C

O=C

O

OH

COOHOH

CCC

O=

OH

O

OH

CO=

OH

OH C=OCH3

CH2

DOC

-OCl-OBr

CX3CN

DBPs

Drinking water concernDrinking water concern

Study designStudy design

Collect samples of surface and subsurface Collect samples of surface and subsurface waters for DOC and THMFP analyseswaters for DOC and THMFP analyses

Combine with water flux data to calculate Combine with water flux data to calculate loadsloads

Monitoring planMonitoring plan Surface inflow and outflow Surface inflow and outflow

Continuously monitored for water fluxContinuously monitored for water flux Weekly sampling for DOC and THMFPWeekly sampling for DOC and THMFP

PiezometersPiezometers Sampled soil water 2x/yr for seasonal Sampled soil water 2x/yr for seasonal

extremes in 2 depths at 3 piersextremes in 2 depths at 3 piers Shallow soils (0.5-2 ft)Shallow soils (0.5-2 ft) Deep peat (8-10 ft)Deep peat (8-10 ft)

Water flux out of the pondWater flux out of the pond

0

400

800

1200

1600

2000

10/1/2001 12/30/2001 3/30/2002 6/28/2002 9/26/2002date

wat

er f

lux

(m3/

day

)

outlet ETo seepage

Water flux (2001-2002)Water flux (2001-2002) Siphon > 95% ET = 10% Outflow = 70% ?

Seep = 20%

Demo pond surface water Demo pond surface water DOCDOC

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

Oct-01 Nov-01 Jan-02 Mar-02 May-02 Jul-02 Sep-02

DO

C (

mg

/L)

inflow outflow 1 outflow 2

DOC concentrations in soil water DOC concentrations in soil water underlying the pondunderlying the pond

0

20

40

60

80

100

120

140

160

180

200

Jan-00 Jul-00 Jan-01 Jul-01 Jan-02 Jul-02 Jan-03 Jun-03 Dec-03 Jun-04 Dec-04

DO

C (

mg

/L)

hdp hsp jdp jsp kdp ksp

DOC loads (2001-2002)DOC loads (2001-2002) Siphon = 940 kg/yr Outflow ~ 1260 kg/yr ?

Seep ~ 2680 kg/yr

THMP loads (2001-2002)THMP loads (2001-2002) Siphon = 120 kg/yr Outflow ~ 160 kg/yr ?

Seep ~ 270 kg/yr

Compare net loads to agCompare net loads to agDOC loads

0

20

40

60

80

100

120

140

160

180

200

Demo pond Ag field 1 Ag field 2

DO

C (

g/m

2-yr

)

agriculture

seepage

surface water

THMP loads

0

2

4

6

8

10

12

14

16

18

20

Demo pond Ag field 1 Ag field 2

TH

MP

s (g

/m2-

yr)

agriculture

seepage

surface water

Temporal trendsTemporal trends

Surface water fluxes show strong Surface water fluxes show strong seasonal trendseasonal trend

Subsurface DOC concentrations are Subsurface DOC concentrations are decreasing over time in some decreasing over time in some shallow soil water (2001-2004) shallow soil water (2001-2004)

DOC concentrations in surface DOC concentrations in surface water (2001-2002)water (2001-2002)

0

1

2

3

4

5

6

Oct

ob

er

No

vem

be

r

De

cem

be

r

Jan

ua

ry

Fe

bru

ary

Ma

rch

Ap

ril

Ma

y

Jun

e

July

Au

gu

st

Se

pte

mb

er

DO

C (

mg

/L)

outflowinflow

Net DOC flux out of the pond Net DOC flux out of the pond (surface waters, 2001-2002)(surface waters, 2001-2002)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Octo

ber

No

vem

ber

De

cem

ber

Janu

ary

Feb

ruary

Ma

rch

April

Ma

y

June

July

Augu

st

Septe

mbe

r

OC

flu

x (

g/m

2)

DOC (g/m2-mo)

THMFP (surface water) THMFP (surface water)

0

100

200

300

400

500

600

700

Oct

ob

er

No

vem

be

r

De

cem

be

r

Jan

ua

ry

Fe

bru

ary

Ma

rch

Ap

ril

Ma

y

Jun

e

July

Au

gu

st

Se

pte

mb

er

TH

MP

(u

g/L

)

outflow

inflow

Net THMP flux from the pond Net THMP flux from the pond (surface waters, 2001-2002)(surface waters, 2001-2002)

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0.350O

cto

be

r

No

ve

mb

er

De

ce

mb

er

Ja

nu

ary

Fe

bru

ary

Ma

rch

Ap

ril

Ma

y

Ju

ne

Ju

ly

Au

gu

st

Se

pte

mb

er

TH

M p

rec

urs

or

flu

x (

g/m

2)

THM

Subsurface trendsSubsurface trends

0

20

40

60

80

100

120

140

160

180

200

Jan-00 Jul-00 Jan-01 Jul-01 Jan-02 Jul-02 Jan-03 Jun-03 Dec-03 Jun-04 Dec-04

DO

C (m

g/L)

hdp hsp jdp jsp kdp ksp

Subsurface fluxes Subsurface fluxes (estimated)(estimated)

Seepage governed by hydraulic headSeepage governed by hydraulic head ~240 m3/day~240 m3/day

Concentration in shallow soils Concentration in shallow soils declined over timedeclined over time Pier H (2001) = 60 mg/L ~ 200 g/mPier H (2001) = 60 mg/L ~ 200 g/m22-yr-yr Pier H (2004) = 25 mg/L ~ 85 g/mPier H (2004) = 25 mg/L ~ 85 g/m22-yr-yr Pier K ~ 160 mg/L ~ 440 g/mPier K ~ 160 mg/L ~ 440 g/m22-yr -yr

Temporal trend summaryTemporal trend summary

Wetland net surface fluxes are seasonalWetland net surface fluxes are seasonal Higher in summer and lower in winterHigher in summer and lower in winter Opposite trend of ag operationsOpposite trend of ag operations

Subsurface fluxesSubsurface fluxes No apparent seasonal trend (lack of data?)No apparent seasonal trend (lack of data?) Concentration (fluxes) have been decreasing Concentration (fluxes) have been decreasing

over time for soils in flow pathover time for soils in flow path

DOC “quality”?DOC “quality”?

DOC quality differs in source of DOC and DOC quality differs in source of DOC and processing in the environmentprocessing in the environment We would expect ag, wetland soil, and We would expect ag, wetland soil, and

surface water DOC to differ in qualitysurface water DOC to differ in quality Food source vs drinking water problem?Food source vs drinking water problem?

Different carbon structures react differently Different carbon structures react differently in DBP formationin DBP formation

Some DOC structures are tasty some are notSome DOC structures are tasty some are not

DOC “quality”DOC “quality”

5

6

7

8

9

10

11

12

13

14

15

0.02 0.04 0.06 0.08 0.1 0.12 0.14SUVA

ST

HM

FP

demo pond surface water

agricultural surface soil water

permanently flooded soil water

ConclusionsConclusions Demo pond contributes more DOC and THMPs Demo pond contributes more DOC and THMPs

to Delta waters than nearby ag fields (>10x)to Delta waters than nearby ag fields (>10x) Most of demo pond loads derived from Most of demo pond loads derived from

seepage through the shallow soilsseepage through the shallow soils If contribution from shallow soils minimized…If contribution from shallow soils minimized…

Demo pond loads would be more comparable to ag Demo pond loads would be more comparable to ag operations (DOC ~2x, THMPs ~4x)operations (DOC ~2x, THMPs ~4x)

Timing of loads would be different from ag Timing of loads would be different from ag operations (benefits?)operations (benefits?)

Demo pond surface water DOC is more Demo pond surface water DOC is more reactive, but also more likely beneficial for reactive, but also more likely beneficial for food web (?)food web (?)

ImplicationsImplications Design of large-scale wetland restoration Design of large-scale wetland restoration

sites need to consider shallow soil sites need to consider shallow soil contributions to drain flowcontributions to drain flow

Need to consider the effect changing the Need to consider the effect changing the DOC load timing from converted fields will DOC load timing from converted fields will have on Delta ecosystems and drinking have on Delta ecosystems and drinking water facilities?water facilities?

Need to balance potential benefits for Need to balance potential benefits for subsidence mitigation, habitat restoration subsidence mitigation, habitat restoration and food web dynamics with potential and food web dynamics with potential threats to drinking water supplythreats to drinking water supply

Future and ongoing workFuture and ongoing work

Twitchell South pondTwitchell South pond Using lessons from demo ponds to monitor loads Using lessons from demo ponds to monitor loads

before, during, and after conversionbefore, during, and after conversion Expand studies to include other priorities (ie: MeHg)Expand studies to include other priorities (ie: MeHg)

Rice project Rice project Using water management lessons to help determine Using water management lessons to help determine

BMPs for reducing DOC loads from rice fields in BMPs for reducing DOC loads from rice fields in DeltaDelta

Compare conversion of corn fields to rice with Compare conversion of corn fields to rice with conversion to wetland conversion to wetland

Questions?Questions?