Managing Acid Sulfate Soil Risks and Impacts in the Lower Lakes

Transcription

1 Managing Acid Sulfate Soil Risks and Impacts in the Lower Lakes 7 th International Acid Sulfate Soils Conference Vaasa, Finland 2012 Barnett, E., Mosley, L., Jolley, A.M., Seaman, R., Higham, J. and Beal, A. 30 August 2012

2 Coorong and Lakes Alexandrina and Albert 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

3 Lower lakes barrages

4 Water levels in Lake Alexandrina Historical Lake Alexandrina Water Level Water Level (m AHD) _ Year

5 ASS conceptual modelling Source: CSIRO

6 Hydrodynamic modelling Modeling indicated acidification when water levels reach below -0.8 m AHD Source: University of Western Australia

7 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

8 Consequences of low water levels photos: EPA, CSIRO and DEWNR

9 Research program Spatial heterogeneity mapping: net acidity hazard Acid generation: oxidation rate of pyrite Mobilisation dynamics: contaminant generation, neutralisation and transport 3-D geochemical and hydrodynamic modelling (ELCOM CAEDYM): simulations and management scenarios Seawater contaminant mobilisation: laboratory and field studies Source: EPA and DEWNR

10 Management strategies PREVENTION minimise oxidation of ASS by inundation with freshwater (avoid saltwater cation exchange) LOCALISED PREVENTION CONTROL VIA BIOREMEDIATION TREATMENT Temporary bund/regulators: maintain water levels in hotspots Vegetation: reduce evaporation and soil temp, and increase soil moisture; less soil erosion Organic carbon inputs: increase sulfate reducing bacterial activity, generates alkalinity Irrigation Neutralisation: via ultrafine limestone (not hydrated lime) Groundwater mounding Chemical ameliorants monitor water level and quality, soil and groundwater parameters

11 Localised prevention Construction 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

12 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 source: SCU photos: SCU, Rural Solutions and DEWNR

13 Treatment Add ultrafine limestone to neutralise acidic waterbodies and soils photos: EPA Rural Solutions and DEWNR

14 mid return of inflows (Basin flooding) Historical Lake Alexandrina Water Level and Salinity Water Level (m AHD) _ Series2 Full Supply Level (0.75m AHD) Surcharge Level (0.85m AHD) 0.35m AHD 5 day, 5 station average salinity Salinity (EC) Year

15 Ongoing issues - salinity Lake Alexandrina - Conductivity/Salinity Middle Point McLeay Top Polltaloch Opening Wellington Islands Milang 6/07/09 22/01/10 10/08/10 26/02/11 14/09/11 1/04/12 18/10/ Lake Albert - Conductivity/Salinity Meningie South West Water Level Recorder Opening Narrung 14/10/09 22/01/10 2/05/10 10/08/10 18/11/10 26/02/11 6/06/11 14/09/11 23/12/11 1/04/12 10/07/12 18/10/12 Specific Electrical Conductivity (us/cm) Specific Electrical Conductivity (us/cm) Now less than 1000 EC ~ 20 and 100 ppt (up to 118,500 EC); seawater 35 ppt Current range ~ 3000 to 4500 EC (average ~1500 EC) water cycling

16 Ongoing issues - groundwater acidity, sulfide reaccumulation 2000 Campbell Park Acidity CP-1S CP-3S CP-2S CP-4S 0 ph (1:1 soil:water) Acidity(m g/l CaCO3) Depth (cm) August 2010 February 2011 March 2012 MBO March May-09 5-Aug Oct Jan-10 2-Apr Jun-10 9-Sep Nov Feb-11 7-May Jul Oct-11 2-Jan Mar-12 ph dynamics at the established Phragmites Waltowa site 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

17 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

18 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 Ngarrindjeri people 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

19 Funding through the SA Government s Murray Futures Program by the Australian Government s Water for the Future Initiative 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 Thank you Acknowledgements Google CLLMM or go to: Lakes_Murray_Mouth/The_environment/Acid_sulfate_soils