The Collie Hub projectPotential issues related to

regional groundwater resources

Philip Denby

Regional groundwater resources

• Approximately 60-80% of water usage in south-west Western Australia sourced from groundwater

• Mediterranean climate in south-west WA (hot, dry summers and mild, wet winters

• Research predicts drying climate over next 50 years = increasing pressure on groundwater resources

• Abstraction for public water supply in Perth from groundwater: 45 GL/a in 1996/7 to 120 GL/a in 2009/10. Likely to increase to 165 GL/a for 2010/11.

• Proposed GSWA Harvey 1 located 115 km south of Perth

• Groundwater resources derived primarily from the Perth Basin, a sedimentary sequence up to ~12 km thick

• Perth Basin hosts units from Permian to Quaternary age

• Superficial, Leederville and Yarragadee Formations form significant regional aquifers

• Industrial use of groundwater from Cattamarra Formation

Figure source: Iasky and Lockwood, 2004, GSWA. Record 2004/8

= GSWA Harvey 1

PERTH

Regional geological setting

Local geological setting (<1000 m depth)

Superficial aquifer• Largely unlicensed use for domestic or agricultural use• Groundwater salinity varies from fresh to saline. The aquifer

becomes less permeable to the east, near the Darling Scarp

Leederville aquifer• Up to 200 m thick in the study area• Salinity increase to 2,500 mg/L TDS at base of formation

Cattamarra Formation (Yarragadee aquifer)• Licensed use limited to industrial operations 40 km to north-east

of study area• Groundwater near Harvey Line: high salinity >30,000 mg/L TDS

below 500 m depth, though little data below 800 m bgl

Major aquifers in the study region

Yarragadee aquifer• Upper Jurassic fluvial

sandstone (up to 3 km thick)

• Sands typically comprise 80-95% of the formation

• Significant abstractions where present in Perth Basin

• Absent in proposed Collie Hub project location

Groundwater monitoring• Network of DoW

monitoring bores across the Perth Basin

• Data used to map aquifer characteristics and used for groundwater modelling

• Targeted program in place to improve monitoring network across the state

= GSWA Harvey 1

• Increasing use of 3D modelling to improve conceptual understanding of geology/hydrogeology

• Increasing use of automation (e.g. data loggers for higher frequency of records)

• Ongoing investigation target knowledge gaps (e.g. Murray-Peel investigation) Distribution of sub-units of the

Yarragadee Formation in the southern Perth Basin

Improvements in understanding of regional hydrogeology

Modelling in Petrel giving new insights into understanding geology and hydrogeology of the Perth Basin

Groundwater investigations in the study region• Additional monitoring bores

shall be installed north of the proposed investigation site

• Part of the Department of Water’s State Groundwater Investigation Program (SGIP)

• Investigation will target the Leederville and Cattamarra aquifers (start mid-2011) to improve monitoring coverage and feed into allocation plans

• Lack of significant hydrogeological data in the study area (e.g. groundwater quality in the ‘target’ formations)

• What is the potential impact of CO2 injection on existing groundwater quality and formation geochemistry?

• Structural geology needs better definition – will this have any impact on CO2 migration?

• Are shallow (i.e. <1000 m deep) groundwater resources in the region at risk of contamination from vertical migration of CO2 ?

• Will potentially useable sources of groundwater above the injection point be isolated?

What are some of the DoW’sconcerns about CCS?