30 August 2012

Managing Acid Sulfate Soil Risks and Impacts in the Lower Lakes

7th International Acid Sulfate Soils Conference

Vaasa, Finland 2012

Barnett, E., Mosley, L., Jolley, A.M., Seaman, R., Higham, J. and Beal, A.

Environmental and cultural significance:• Declared a wetland of international importance in 1985 (Ramsar)• Coorong National Park• Estimated the area receives over 200,000 visitors per year• The traditional owners of the region are the Ngarrindjeri people

Coorong and Lakes Alexandrina and Albert

Lower lakes barrages

Water levels in Lake Alexandrina

Historical Lake Alexandrina Water Level

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1962 1964 1966 1968 1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012Year

Wat

er L

evel

(m A

HD)

_

ASS conceptual modelling

Source: CSIRO

Hydrodynamic modelling

Source: University of Western Australia

Modeling indicated acidification when water levels reach below -0.8 m AHD

Real Time Management Strategy

Approved by the Murray Darling Basin Ministerial Council:

Monitoring water levels and pH (alkalinity) Construction of a bund separating the lakes and

pumping water from Lake Alexandrina to Lake Albert Management triggers:

A minimum 25mg/L of Carbonate in either waterbody

Water levels of -1.5 m AHD in Lake Alexandrina and -0.5 m AHD in Lake Albert

If either met introduce seawater through the Barrages

Action is subject to approvals in the Environment Protection and Biodiversity Conservation Act 1991

photos: EPA and DEWNR

Consequences of low water levels

photos: EPA, CSIRO and DEWNR

Research program

Source: EPA and DEWNR

Spatial heterogeneity mapping: net acidity hazard

Acid generation: oxidation rate of pyrite

Mobilisation dynamics: contaminant generation, neutralisation and transport

Seawater contaminant mobilisation: laboratory and field studies

3-D geochemical and hydrodynamic modelling (ELCOM CAEDYM):simulations and management scenarios

Management strategies

PREVENTIONminimise oxidation of ASS by inundation with freshwater (avoid saltwater cation exchange)

LOCALISEDPREVENTION

CONTROL VIABIOREMEDIATION TREATMENT

Temporarybund/regulators:maintain water levels in hotspots

Vegetation:reduceevaporation and soil temp, and increase soil moisture; less soil erosion

Organic carbon inputs:increase sulfatereducing bacterial activity, generates alkalinity

Neutralisation:via ultrafinelimestone(not hydrated lime)

IrrigationGroundwatermounding

Chemical ameliorants

monitor water level and quality, soil and groundwater parameters

Localised preventionConstruction of the bund and temporary regulators

Goolwa regulator: played fundamental role

in controlling water levels via water pumped from Lake Alexandrina

Currency Creek regulator: risk mitigation to stop the

transport of acidity into the Goolwa Channel

Goolwa regulator near Clayton with pumps Currency Creek regulator with spillway

Bioremediation/revegetation

• Increases organic matter around exposed shorelines for sulfate-reducing bacteria to consume

• Assists in soil erosion control and also provides ecological outcomes for the region

photos: SCU, Rural Solutions and DEWNR

source: SCU

TreatmentAdd ultrafine limestone to neutralise acidic waterbodies and soils

photos: EPA Rural Solutions and DEWNR

mid 2010 - return of inflows (Basin flooding)

Historical Lake Alexandrina Water Level and Salinity

-1.1-1.0-0.9-0.8-0.7-0.6-0.5-0.4-0.3-0.2-0.10.00.10.20.30.40.50.60.70.80.91.0

2004 2005 2006 2007 2008 2009 2010 2011 2012

Year

Wat

er L

evel

(m A

HD)

_

0

1000

2000

3000

4000

5000

6000

7000

Salinity (EC)

Series2

Full Supply Level (0.75m AHD)

Surcharge Level (0.85m AHD)

0.35m AHD

5 day, 5 station average salinity

Ongoing issues - salinity

Lake Albert - Conductivity/Salinity

0

5000

10000

15000

20000

25000

14/10

/09

22/01

/10

2/05/1

0

10/08

/10

18/11

/10

26/02

/11

6/06/1

1

14/09

/11

23/12

/11

1/04/1

2

10/07

/12

18/10

/12Spec

ific

Elec

tric

al C

ondu

ctiv

ity (u

S/cm

) MeningieSouth WestWater Level RecorderOpeningNarrung

Lake Alexandrina - Conductivity/Salinity

0100020003000400050006000700080009000

10000

6/07/0

9

22/01

/10

10/08

/10

26/02

/11

14/09

/11

1/04/1

2

18/10

/12Spec

ific

Elec

tric

al C

ondu

ctiv

ity (u

S/cm

) MiddlePoint McLeayTopPolltalochOpeningWellingtonIslandsMilang

~ 20 and 100 ppt (up to 118,500 EC); seawater – 35 ppt

Current range ~ 3000 to 4500 EC (average ~1500 EC)

Now less than 1000 EC

water cycling

Ongoing issues - groundwater acidity,sulfide reaccumulation

0

5

10

15

20

25

30

35

40

2 4 6 8 10

Dep

th (cm)

pH (1:1 soil:water)

August 2010

February 2011

March 2012

MBO March 2012

pH dynamics at the established PhragmitesWaltowa site

Campbell Park Acidity

0

500

1000

1500

2000

17-M

ay-0

9

5-Au

g-09

24-O

ct-0

9

12-J

an-1

0

2-Ap

r-10

21-J

un-1

0

9-Se

p-10

28-N

ov-1

0

16-F

eb-1

1

7-M

ay-1

1

26-J

ul-1

1

14-O

ct-1

1

2-Ja

n-12

22-M

ar-1

2

Aci

dity

(mg/

L C

aCO

3)

CP-1S CP-2S

CP-3S CP-4S

Acidity remediation via alkalinity:• in the lake waters • organic matter from inundation tolerant vegetation

Sulfate reduction and accumulation of reduced inorganic sulfides(especially pyrite and monosulfides)

Source: EPA, SCU

Input to national guidances and planning

Proposed Basin Plan (Water Act 2007)• Ensure enough environmental water is delivered to the Coorong, Lower Lakes and Murray mouth to support:

• sufficient flows and suitable water levels • salinity export and water quality • ecosystem response

• >10,000 GL/y for consumptive uses• Aim is to return a long-term average of at least 2,750 GL/y with an adjustment mechanism for water savings

Key messages

We have a better understanding of:• Acidification and related risks (metals, MBOs)• Salinity issues and ecological limits of acceptable change

We now have the knowledge to better manage the CLLMM site - management triggers/strategies

We are working with the community and Ngarrindjeripeople to deliver management actions

But…Ecosystem recovery is slow compared to drought impact

We need suitable environmental flows to assist with recovery and avoid future degradation of this unique region

Scientific research committee:•Drs Rob Fitzpatrick, Paul Shand, Warren Hicks (CSIRO) and team•Profs Leigh Sullivan, Richard Bush (Southern Cross University) and team•Dr Matt Hipsey (University of WA)•Dr Jeff Taylor, Sophie Pape (Earth Systems)• Dr Freeman Cook•Drs John Cugley (Chair), Luke Mosley, Liz Barnett

Agency staff:Ann Marie Jolley, Jason Higam, Russell Seaman, Ceridwen Synnot, Andrew Beal Richard Brown, Ben Zammit, Clive Jenkins, Shaun Thomas, Emily Leyden, Dylan Stone

Community members:Colin Grudy, Mike South , Anne Hartnett for land access and assistance

Funding through the SA Government’s Murray Futures Program by the Australian Government’s Water for the Future Initiative

Thank youAcknowledgements

Google CLLMMor go to:

http://www.environment.sa.gov.au/Conservation/Rivers_wetlands/Coorong_Lower_Lakes_Murray_Mouth/The_environment/Acid_sulfate_soils