Ecohydrological Conceptualisation of the Fortescue Marsh Region
Existing and potential stressors
Yüklə 12,45 Mb. Pdf görüntüsü
|
Existing and potential stressors Existing mining projects proximal to the Marsh include the FMG Cloudbreak and Christmas Creek operations along the northern margins. To the east, the RHIO Roy Hill project is under development with various early preparation works now completed. Additional mining proposals south of the Marsh including FMG Nyidinghu and Brockman Mining Limited Marillana. BHP Billiton Iron Ore and Rio Tinto have existing and proposed mines in upper catchment areas of the Weeli Wolli Creek. Key indicators Based on the ecohydrological conceptualisation of the Marsh, t he following key indicators for the preservation of the ecological values of the Marsh are proposed: Volumes of surface and groundwater inflows to the Marsh. Flooding frequency, duration and spatial extent. Depth to watertable. Samphire vegetation health. Aquatic invertebrate assemblages (species diversity and abundance). Waterbird species diversity and abundance. Ecohydrological Conceptualisation of the Fortescue Marsh Region Status: Final September 2015 Project No.: 83501069 Page 108 Our ref: FM-EcoConcept_v8.docx Figure 4-15: Ecohydrological conceptualisation of the Fortescue Marsh Ecohydrological Conceptualisation of the Fortescue Marsh Region Status: Final September 2015 Project No.: 83501069 Page 109 Our ref: FM-EcoConcept_v8.docx 4.3 Ecological receptor - Freshwater Claypans of the Fortescue Valley PEC (EHU 9) This section of the report addresses the freshwater claypans of the Fortescue Valley PEC, including restating some information presented in earlier sections. Ecological information on the Freshwater Claypans is included in Sections 4.3.1 to 4.3.3, with hydrological and ecohydrological aspects presented in later sections. 4.3.1 Overview The Freshwater Claypans of the Fortescue Valley is recognised as a Priority 1 Ecological Community (PEC) by the Department of Parks and Wildlife (DPaW) (DPaW, 2013). There are five occurrences of this PEC in the Fortescue Valley west of the Goodiadarrie Hills, with three in the study area summarised as follows (Map 4-02): East Claypan - located approximately 2 km west of the BHP Billiton Iron Ore railway line; Central Claypan - located 13 km west of the BHP Billiton Iron Ore railway line; and West Claypan - located approximately 4 km west of the Great Northern Highway. All of these claypans are relatively small in size and are situated south of the BHP Billiton Iron Ore Roy Hill tenements (Map 4-02). 4.3.2 Previous work There is little published information on the hydrology and ecology of the claypans constituting the freshwater claypans of the Fortescue Valley PEC. Between 2003 and 2006, Pinder et al. (2010) sampled water quality and aquatic invertebrates in the two PEC claypans west of the study area, as a component of the Pilbara Biological Survey (Table 4-5). A high diversity of aquatic invertebrates was observed, with major differences in assemblages between sampling dates (for each claypan respectively less than 15% of the total number of sampled taxa were collected on every sampling date). Between 2004 and 2005, Halse et al. (2010) measured the depth to groundwater and sampled water quality in a station bore 2.5 km south west of the West Claypan ( Table 4-6). The depth to groundwater was about 4 m and groundwater salinity around 4000 µs/cm EC. 4.3.3 Ecological description The Freshwater Claypans of the Fortescue Valley PEC are important for waterbirds, invertebrates and some poorly collected plants (Eriachne spp, Eragrostis spp. grasslands) (DPaW, 2013). It is a unique community characterised by having relatively few Western Coolibah trees ( Eucalyptus victrix) and expansive bare clay flats (Map 4-02). The fringing Western Coolibah trees at the claypans, although at low density, may provide an important structural element for waterbird roosting and nesting. The flood regime may influence tree water use, through soil water replenishment and vegetation population dynamics (e.g. recruitment and senescence). Flood frequency has been correlated with overstorey tree health in semi -arid wetlands in eastern Australia (McGinness et al., 2013); and has also been linked to flowering, seed production, seed germination and seedling recruitment dynamics (Jensen et al., 2008). The long -term persistence of such wetland woodland communities requires sufficient recruitment/regeneration to compensate for adult tree mortality. The ephemeral nature of the claypans is an important factor affecting aquatic invertebrate assemblages and use of the claypans by waterbirds. The high diversity of aquatic invertebrates may be related to high biotic diversity in riverine refugia, which promote high floodplain diversity following floods (Pinder et al., 2010). High turbidity may also be an important factor affecting the aquatic invertebrate species assemblages. Turbidity can limit macrophyte growth and affect algal production through light limitation, resulting in benthic primary productivity being largely restricted to the edge of the waterbody (Bunn et al., 2003; Fellows et al., 2007). Turbidity may assist some invertebrate species to more easily evade predation by waterbirds (Pinder et al., 2010). The claypans and their surrounding catchments have been subjected to an extended period of pastoral land use, which is likely to have influenced catchment characteristics and vegetation communities. Ecohydrological Conceptualisation of the Fortescue Marsh Region Status: Final September 2015 Project No.: 83501069 Page 110 Our ref: FM-EcoConcept_v8.docx Table 4-5: Data collected by Pinder et al. (2010) from freshwater claypans of the Fortescue Valley PEC located west of the study area DPaW Site Code and Location Units PSW004 (652098E; 7549388N) PSW005 (643987E; 7553451N) Sampling Date 24/05/2004 18/08/2003 30/08/2006 24/05/2004 18/08/2003 30/08/2006 Altitude mASL 404 404 404 406 406 406 Turbidity NTU 340 0.7 7 400 490 2.1 Total dissolved solids (TDS) mg.L -1 120 190 75 88 140 87 Maximum depth of invertebrate sample (Depth) cm 62 35 60 104 70 150 Biomass of submerged macrophytes (SubMB) g.m 2 0 87.1 4.5 0 0.8 17.4 % Cover of submerged macrophytes (SMC) % 0 80 20 0 1 90 % Cover of emergent macrophytes (EMC) % 0.5 0 0 2 0 0 pH pH 8.1 9.33 9.21 7.72 8.09 9.13 Total filterable nitrogen (TFN) mg.L -1 0.84 1 0.43 0.39 1.7 0.57 Total filterable phosphorus (TFP) mg.L -1 0.03 0.01 0.02 0.02 0.21 0.02 Total chlorophyll (Chl) mg.L -1 0.0045 0.1495 0.002 0.0065 0.028 0.002 Water temperature (Temp) ºC 24.7 25.6 23.9 28 22.5 24.4 Colour TCU 37 13 15 37 17 11 Alkalinity mg.L -1 87 110 50 62 115 55 Hardness mg.L -1 23 25 20 22 359 19 Silica mg.L -1 11 15 3.1 7.8 11 7.9 Number of aquatic invertebrate taxa (diversity) 98 91 81 106 91 112 Ecohydrological Conceptualisation of the Fortescue Marsh Region Status: Final September 2015 Project No.: 83501069 Page 111 Our ref: FM-EcoConcept_v8.docx Table 4-6 Data collected by Halse et al. (2014) from a station bore located 2.5 km southwest of the West Claypan Bore ID Units PSS284 Mulga1 (675434E; 7536782N; Altitude 411mASL) Sampling Date 23/06/2004 15/08/2005 Depth to water m 3.8 4.25 Depth to bottom m 5 5.85 Turbidity NTU 22 0.7 Colour TCU 2.5 2.5 TDS mg/L 1.9 2.8 Alkalinity mg/L 303 295 Hardness mg/L 540 630 SiO 2 mg/L 71 94 Na mg/L 614 692 Ca mg/L 76.8 89.4 Mg mg/L 83.8 99.8 K mg/L 39 42.1 Mn mg/L 0.0025 0.0005 Cl mg/L 750 873 HCO 3 mg/L 369 360 CO 3 mg/L 1 1 NO 3 mg/L 5.8 9.1 SO 4 mg/L 485 577 Fe mg/L 0.0025 0.0025 Sr mg/L 0.55 0.67 EC µS/cm 3757 4415 Field pH 6.81 6.79 TN mg/L 6300 13000 TP mg/L 30 5 Temp °C 24.9 27.27 DO % 41.1 61.9 DO mg/L 3.1 4.9 Redox mV 406 504 Ecohydrological Conceptualisation of the Fortescue Marsh Region Status: Final September 2015 Project No.: 83501069 Page 112 Our ref: FM-EcoConcept_v8.docx 4.3.4 Surface water The three freshwater claypans (East, Central and West) are located within the BHP Billiton Iron Ore Roy Hill West catchment (Map 4-02). This catchment occupies 725 km 2 of the Goodiadarrie Swamp catchment, which has a total area 4,138 km 2 (Map 3-01). Each claypan is associated with a discrete catchment area. The catchment rainfall-runoff response and distribution of EHUs within the BHP Billiton Iron Ore Roy Hill West catchment are considered to be similar to those of the catchments located on the northern fringes of the Marsh. There is an even distribution of upland areas (EHU 1) and alluvial plains (EHU 6) in the catchment (Map 4-01, Map 4.02, and Figure 4-16). Runoff from the eastern and central Claypan catchments flow directly into the East and Central claypans respectively; while the Western Claypan is located within a small localised catchment. Assessment of the 5m DEM levels suggests that runoff from the upstream surface water sub -catchments of the BHP Billiton Iron Ore Roy Hill West catchment will flow directly into the Fortescue River and do not contribute any surface water inflow to this claypan. Based on similarities of catchment characteristics and EHU distributions in the Newman and Claypan catchments, the Newman catchment rainfall-runoff relationships, as discussed in Section 3.1.3, and adjusted for shorter flow distances and differences in alluvial plain areas (Section 4.2.6) , have been applied to the claypan catchments to simulate runoff from these catchments. Similar to the Fortescue Marsh catchments, flooding is generally associated with cyclonic rainfall and runoff in the summer months. As shown in Figure 4-16, runoff into the claypans is estimated to be about 3% of annual rainfall, with significant catchment losses (infiltration, evaporation and ev apotranspiration). The assumed runoff coefficient of around 3% corresponds to the median annual runoff for Fortescue River at Newman (i.e. lower than the average annual runoff coefficient of 5.3%). Figure 4-16: Conceptual water balance for the East and Central Claypans Rainfall CP Central (186km 2 ) Claypan Central Catchment 68 GL/yr Losses 71 GL/yr 2 GL/yr 100% contribution to CP Central Runoff Rainfall CP East (247km 2 ) Claypan East Catchment 91 GL/yr Losses 94 GL/yr 3 GL/yr 100% contribution to CP East Runoff Ecohydrological Conceptualisation of the Fortescue Marsh Region Status: Final September 2015 Project No.: 83501069 Page 113 Our ref: FM-EcoConcept_v8.docx 4.3.5 Groundwater The claypans are underlain by shallow alluvium and Tertiary Detritals, in a sequence presumed similar to the Fortescue Valley. The depth to watertable beneath the claypans is unknown, but considered likely to be in the range of two to four metres below ground level. The level of connectivity of the groundwater system with the surface environment is unknown. The position of the watertable is maintained by the balance of groundwater inflow from the Chichester Range and evapotranspiration. Monitoring instrumentation needs to be installed to provide an understanding of the role groundwater has, if any, in the hydrological regime of the claypans. 4.3.6 Ecohydrological conceptualisation The key features of the ecohydrological conceptualisation of the Freshwater Claypans of the Fortescue Valley PEC are depicted in Figure 4-17 and summarised as follows: Surface and groundwater systems Surface water runoff from the surrounding catchments is attenuated in the internally draining low-relief landscape of the claypans. The estimated flooding frequency may be similar to the Fortescue Marsh and could range between 1 in 5 years to 1 in 27 years based on the hydrological analysis for the Marsh (Section 4.2). No information is available on flood levels/regimes that would be required to support the claypan ecosystems. Soil moisture in the shallow sediments of the claypans is replenished by a combination of rainfall and surface inflows. The ephemeral waterbodies of the claypans rapidly evaporate post flooding. Large floods exceed the storage volume of the claypans, and via flushing prevent significant accumulation of salts (in contrast with the Fortescue Marsh environment). Groundwater levels may range between 2 and 4 m bgl. Little is known of the hydrostratigraphy beneath the claypan surfaces. The claypans are assumed to be underlain by low permeability sediments, which may constitute a barrier to groundwater recharge and discharge. Further investigations are required to confirm this. Ecosystem components The expansive bare clay flats are fringed with Western Coolibah and tussock grassland vegetation communities. The Western Coolibah trees may rely on stored soil moisture replenished by flooding to meet their water requirements. The claypans support diverse aquatic invertebrate assemblages during flood events. Waterbody ephemerality, turbidity and connectivity with the broader Fortescue River floodplain may be key factors affecting the species composition. These factors will vary interannually and between seasons. The claypans provide foraging habitat for waterbirds, and ma y also provide breeding habitat. Existing and potential stressors There are currently no mining activities in the catchments of the West , Central and East Claypans respectively. Key Indicators Based on the ecohydrological conceptualisation of the Freshwater Claypans of the Fortescue Valley PEC, the following key indicators for the preservation of the ecological values of the PEC are propos ed: 1. Flooding frequency. 2. Depth to groundwater (unless shown to be disconnected from the surface environment). 3. Tree health (Western Coolibahs). 4. Aquatic invertebrate assemblages (species diversity and abundance). 5. Waterbird species diversity and abundance. Ecohydrological Conceptualisation of the Fortescue Marsh Region Status: Final September 2015 Project No.: 83501069 Page 114 Our ref: FM-EcoConcept_v8.docx Figure 4-17: Ecohydrological conceptualisation of the Claypans Ecohydrological Conceptualisation of the Fortescue Marsh Region Status: Final September 2015 Project No.: 83501069 Page 115 Our ref: FM-EcoConcept_v8.docx 5 Stressors 5.1 Marillana The BHP Billiton Iron Ore Marillana Iron Ore Project is approximately 100 km northwest of Newman and 16 km northeast of BHP Billiton Iron Ore ’s mining area at Yandi (Map 5-01), within the Upper Fortescue River Catchment along the northern edge of the Hamersley Range and southern side of the Fortescue River Valley. The project is approximately 9 km to the south of the closest part of the Fortescue Marsh. The proposed project comprises fourteen open-cut pits (MA-A to MA-N), eight proposed OSAs (MA-1 to MA-8) and three proposed infrastructure areas (MI-1 to MI-3). The proposed study area plan also includes a conceptual railroad alignment (Map 5-01). The proposed footprint covers an area of 31 km 2 out of the total mining tenement M 270SA area of 115 km 2 . BHP Billiton Iron Ore have undertaken preliminary hydrogeological field investigations (RPS, 2012) enabling the development of a conceptual hydrogeological model. This has been incorporated into a numerical groundwater model that predicts groundwater response to dewatering scenarios related to a proposed mining plan and schedule (based on Preliminary_Mine_Sequence_hydrology.xlsx an d 054 alignments.dxf). No detailed surface water investigations have been undertaken to evaluate the potential impacts and influence of episodic flow events in the Weeli Wolli and Koodiaderi Creeks, as they discharge into the Fortescue River Valley and towards Fortescue Marsh. Table 5-1 provides an overview of the Marillana orebody. 5.1.1 Conceptualisation 5.1.1.1 Surface water The Weeli Wolli Creek is the main surface water feature that episodically flows through and adjacent to the south east corner of the tenement. The main creek channel flows in a north to north westerly direction terminating in the Fortescue Marsh. At a regional scale, the Fortescue Marsh located to the north is the most significant surface water feature being an evaporative sink and regional termini for surface water catchments. There is no direct surface water flow from the Marillana deposit that reaches the Marsh. 5.1.1.2 Groundwater The Marillana iron ore deposits consist of a combination of bedrock mineralisation within the Brockman Iron Formation members and localised overlying Tertiary detrital, scree, pisolite and CID deposits that occur along the northern flank of the Hamersley Range. An interpretive geological cross-section is presented in Figure 5-1. The main bedrock aquifers are the mineralised orebodies within the Brockman Iron Formation (Dales Gorge Member, Whaleback Shale and Joffre Member), that have undergone preferential leaching resulting in enhanced secondary permeability within the ore zones and the associated partially mineralised halo zone. The unmineralised BIF and underlying shale units (Mt McRae Shale and Mount Sylvia Formation) have generally low permeability which restricts vertical and in some locations horizontal hydraulic connection. To the north and outside the Marillana tenements, the Poonda Fault is concealed by the Tertiary sediments. This fault may contribute to hydraulic connection between orebody aquifers and the potentially highly weathered and cavernous dolomite of the Wittenoom Formation. Aquifers within the Tertiary sedimentary sequence include localised, ephemerally saturated colluvium and detrital deposits generally marginal to the northern edge of the Hamersley Range (may be perched aquifers). Aquifers exist within the Weeli Wolli Creek alluvium, pisolites, gravels and CID deposits have highly variable extents and continuities. A broad scale calcrete aquifer, considered to be the Oakover Formation, is present within the Tertiary sediment sequence at or below the regional watertable extending from the south and outcropping near the edge of the Fortescue Marsh. These aquifers are expected to become increasingly confined with depth. Ecohydrological Conceptualisation of the Fortescue Marsh Region Status: Final September 2015 Project No.: 83501069 Page 116 Our ref: FM-EcoConcept_v8.docx Groundwater flow is generally to the north towards the Fortescue Marsh, with water levels broadly mimicking topography. Depth to water potentially ranges from more than 150 m bgl at the top of Hamersley Range to about 20 m bgl in proximity to Weeli Wolli Creek. The orebodies occurring at higher elevations in the Hamersley Range are likely to have limited or no hydrological connectivity with the detritals in the Fortescue Valley. Orebodies at lower elevations are likely to be at least partly connected with detritals in the Fortescue Valley. Faults and dolerite dykes are known to propagate through the tenement and may act as conduits or barriers to groundwater flow. The Wittenoom Formation containing upper horizons of enhanced permeability may, in places, be in direct connection with orebody aquifers, notably where associated with the Poonda Fault. Recharge contribution to the shallow aquifer from the Weeli Wolli Creek is expected to be small, given that median flows in the Weelli Wolli Creek within the Fortescue Valley are relatively small (2 to 4 GL/yr) and the depth to watertable is greater than 30 m bgl. High flows that occur infrequently have a greater potential to provide recharge to the underlying shallow aquifer. Recharge from incidental rainfall, localised streamflow and sheetflow may occur along the foothills of the range into the detrital units (RPS, 2012). Groundwater quality within the orebodies is generally fresh to brackish with salinity increasing slightly with depth. A significant regional saline-hydersaline groundwater body is known to exist to the north of the Marillana Project associated with the Fortescue Marsh, however its on impact on dewatering activities at Marillana is considered to be limited. Kataloq: media media -> Uşağın fərdi psixoloji hazırlığı 20 azn ağız boşluğunun kompleks peşəkar gigiyenası 80 azn media -> Tibb xidmətinin adı media -> Әrin cәmi vә hәr bir kateqoriya üzrә mәblәği vә kredit portfelindә xüsusi çәki media -> Qeyri-standart kreditlәrin cәmi vә hәr bir kateqoriya üzrә mәblәği vә kredit portfelindә xüsusi çәkisi media -> Ramiz ƏSKƏr türk xalqlari əDƏBİyyati oçerkləRİ-1 Bakı – 2011 media -> AZƏrbaycan miLLİ elmlər akademiyasi folklor institutu qarabağ: folklor da bir tariXDİr V kitab Yüklə 12,45 Mb. Dostları ilə paylaş:
|