REPORT Ecohydrological Conceptualisation of the Fortescue Marsh Region Prepared for BHP Billiton Iron Ore September 2015 This report has been prepared solely for the purposes of informing environmental impact assessment pursuant to the Environmental Protection Act 1986 (WA) and Environment Protection and Biodiversity Conservation Act 1999 (Cth) and is not intended for use for any other purpose. No representation or warranty is given that project development associated with any or all of the disturbance indicated in this report will actually proceed. As project development is dependent upon future events , the outcome of which is uncertain and cannot be assured, actual development may vary materially from this report. Ecohydrological Conceptualisation of the Fortescue Marsh Region This document has been prepared for the benefit of BHP Billiton Iron Ore. No liability is accepted by this company or any employee or sub-consultant of this company with respect to its use by any other person. This disclaimer shall apply notwithstanding that the report may be made available to other persons for an application for permission or approval to fulfil a legal requirement. QUALITY STATEMENT PROJECT MANAGER PROJECT TECHNICAL LEAD Tracy Schwinkowski Milo Simonic PREPARED BY Milo Simonic ………………………………............... 02/09/2015… CHECKED BY Johan van Rensburg ………………………………............... 02/09/2015… REVIEWED BY Gary Clark ………………………………............... 02/09/2015… APPROVED FOR ISSUE BY Milo Simonic ………………………………............... 02/09/2015… PERTH 41 Bishop Street, Jolimont WA 6104 Ph: 08 9388 8799 Fax: 08 9388 8633 REVISION SCHEDULE Signature or Typed Name (documentation on file). Rev Date Description No Checked Prepared by Reviewed by Approved by by 1 19/03/14 Draft– Sections 1 to 4 MS, DH, JvR, MS, DH GC LvdW LvdW BP 2 7/05/14 Final Sections 1 to 4 MS, DH, JvR, MS, LvdW DH LvdW LvdW BP 3 12/05/14 Final Sections 1 to 4, Draft for MS, DH, JvR, MS, DH GC LvdW comment Sections 5 to 7 LvdW BP 4A 13/06/14 Final MS, DH, JvR, MS, DH GC LvdW BP 5 18/07/14 Final with third party stressors GC, MS, JvR LvdW GC LvdW 6 17/10/14 Final with SEA comments MS, JvR GC GC GC 7 08/05/15 Final with map update MS JvR GC MS 8 02/09/15 Final with minor updates MS JvR GC MS Status: Final – Rev 7 Project No.: 83501069 September 2015 Our ref: FM-EcoConcept_v8.docx Ecohydrological Conceptualisation of the Fortescue Marsh Region Executive Summary Introduction This report describes an ecohydrological conceptualisation of the Fortescue Marsh (the Marsh) Region and surrounding catchment areas. The project extent was defined based on catchment scale hydrology and the position of BHP Billiton Iron Ore’s proposed mining projects within the vicinity of the Marsh. It covers an area of 11,971 km2 bound by the Chichester Range in the north; the Upper Fortescue River to the east; the Hamersley Range to the south; and a surface water and inferred groundwater divide in the west that separates the Goodiadarrie Swamp from the Lower Fortescue River. Despite BHP Billiton Iron Ore having no current mining operations near the Marsh, there are several proposed mining areas including Marillana, Mindy, Coondiner, and Roy Hill. Study objectives The objectives were to provide: an understanding of the natural water resource system (hydrology and hydrogeology), and key ecohydrological components, linkages and processes; a basis for assessing potential hydrological change associated with BHP Billiton Iron Ore operations (current and future) on the water resources, with particular focus on the interaction between key environmental receptors and the orebodies; and a knowledge foundation for future numerical modelling of ecohydrological processes associated with the Marsh and surrounding areas. Ecohydrological conceptualisation Nine landscape ecohydrological units (EHUs) were defined. Each EHU represents a landscape element with broadly consistent and distinctive ecohydrological attributes being summarised as. EHU 1 - Upland source areas: hills, mountains, plateaux. EHU 2 - Upland source areas: dissected slopes and plains. EHU 3 - Upland transitional areas: drainage floors within EHUs 1 and 2 which tend to accumulate surface flows from up-gradient. EHU 4 - Upland channel zones: channel systems of higher order streams which are typically flanked by EHU 3 and dissect EHUs 1 and 2. EHU 5 - Lowland sandplains: level to gently undulating surfaces with occasional linear dunes. Little organised drainage but some tracts receive surface water flow from upland units. EHU 6 - Lowland alluvial plains: typically of low relief and featuring low energy, dissipative drainage. EHU 7 - Lowland calcrete plains: generally bordering major drainage tracts and termini, typically with shallow soils and frequent calcrete exposures. EHU 8 - Lowland major channel systems and associated floodplains. EHU 9 - Lowland receiving areas: drainage termini in the form of ephemeral lakes, claypans and flats. Existing environment The climate of the study area is semi-arid to arid, characterised by high temperatures and low, irregular rainfall. Most rainfall occurs between December and March in association with tropical cyclones and localised thunderstorms. The east-west trending Fortescue River Valley separates the Hamersley Range (to the south) and Chichester Range (to the north). The Marsh is a brackish to saline, endorheic wetland formed in Status: Final Rev 7 Page iv September 2015 Project number: 83501069 Our ref: FM-EcoConcept_v8.docx Ecohydrological Conceptualisation of the Fortescue Marsh Region the drainage terminus of the Upper Fortescue River within the Fortescue Valley. The Goodiad arrie Hills form the catchment divide between the Upper and Lower Fortescue River catchments. Immediately west of the Goodiadarrie Hills, a series of freshwater claypans constitute the Freshwater Claypans of the Fortescue Valley Priority Ecological Community (PEC) occur in proximity to the Fortescue River channel. The basement geology is dominated by the Hamersley Group which consists of various metasedimentary rocks including cherty banded iron formation, chert and carbonates interbedded with minor felsic volcanic rock and intruded by dolerite dykes. The Fortescue Valley is a flat-lying, complex sequence of Quaternary and Tertiary alluvial, colluvial and lacustrine sediments overlying the basement. The alluvial deposits increase in thickness away from the ranges towards the Marsh. The vegetation of the Hamersley and Chichester Ranges is typically open and dominated by spinifex, acacia small trees and shrubs, and occasional eucalypts. On the flats of the Fortescue Valley surrounding the Marsh, the vegetation is a mosaic of spinifex grasslands and Acacia woodlands and shrublands. This includes areas of groved Mulga and Snakewood formations. The major drainages are fringed by eucalypt woodlands and tussock grassland communities. The Marsh consists of sparsely vegetated, clay flats fringed by samphire vegetation communities. It is the largest ephemeral wetland in the Pilbara and has multiple conservation values. The Marsh is classified as a wetland of national importance within the Directory of Important Wetlands in Australia and contains a number of Priority Ecological Communities (PEC). In July 2013, the EPA defined a Fortescue Marsh Management Area consisting of seven sub- zones partitioned into three conservation significance categories (EPA Report 1484; EPA 2013). The project area encompasses the management zones identified in the Fortescue Marsh Management Area. Portions of the Marsh have been identified for transition into conservation tenure and management, in relation to the expiry of pastoral leases in 2015. Regional hydrology Catchment areas contributing flows to the Marsh include downstream portions of the Fortescue River and Weeli Wolli Creek catchments, as well as Koodaideri, Chuckalong (between Weeli Wolli Creek and Mindy Mindy Creek), Coondiner and Mindy Mindy Creeks. There are minor surface water contributions from Goman, Sandy, Christmas, Kulbee, and Kulkinbah Creeks. The Marsh itself consists of two basin areas (east and west) separated by a slightly elevated divide. The Upper Fortescue River provides the majority of surface water flow to the Marsh, with a catchment area of approximately 31,000 km2.The surface water hydrology is characterised by variable rainfall-runoff response with lower rainfall-runoff response associated with deeper soils and flatter areas, such as the Flat Rocks catchment; and higher rainfall-runoff response associated with steeper slopes and shallower soils, such as the Newman catchment. Groundwater The regional aquifer system is hosted in Tertiary detritals and underlying Wittenoom Formation (dominated by dolomite of the Paraburdoo Member). Tertiary calcrete or pisolitic limonite formed within valley-fill sequences is often highly permeable. The flanks of the valley rise into ranges comprising fractured-rock aquifers of low permeability and storage. In places, these basement rocks have more transmissive sections associated with orebodies and form localised aquifers. The extent of these orebody aquifers and their connectivity with larger groundwater flow systems may be enhanced by faulting or erosion or other structural features, and as such can vary widely and is site specific. Depth to groundwater varies being shallowest beneath the Fortescue Marsh and deeper towards the flanks of the Fortescue Valley and adjacent ranges. Groundwater contribution to the Fortescue Marsh water balance is minor when compared