CONTENTS - Part 2

CONTENTS - Part 2 5 WATER 80 7 BIODIVERSITY 112 10 HERITAGE 146 5.1 Current State 80 7.1 Current State 112 10.1 Current state 146 5.2 Increasing water demand 91 7.2 Altered fire regimes 119 10.2 Loss or degradation of heritage sites 153 5.3 Altered water regimes 92 7.3 Loss or degradation of native vegetation 122 5.4 Contamination 94 7.4 Introduced animals, pests and weeds 125 11 BUILT ENVIRONMENT 154 5.5 Salinisation 95 11.1 Current state 154 8 COASTS 128 11.2 Stormwater management 156 8.1 Current State 128 6 LAND 96 11.3 Energy use 156 8.2 Coastal vulnerability 132 6.1 Current state 96 11.4 Waste generation and disposal 157 8.3 Loss or degradation of coastal habitat 133 6.2 Declining land capability 103 6.3 Acid sulphate soils 109 12 MONITORING & REPORTING FRAMEWORK 158 6.4 Land contamination 111 9 MARINE ENVIRONMENT 136 12.1 Indicators and measuring change 158 9.1 Current State 136 9.2 Degradation of the marine environment 141 9.3 Introduced pests 144 13 REFERENCES 164 9.4 Over-fishing 145 Appendix A – BIodiversity listings 167 Pilbara state of the environment rePort 2013 5. WATER 5.1 CuRREnT STATE of the central Pilbara and discharge over the Most runoff occurs during the period January to systems. The flood potential of a system is coastal plains into the Indian Ocean. The east March, largely as a result of cyclonic activities, not directly related to cyclone intensity but is As noted in section 3.3, the Pilbara Pilbara is drained predominantly by the Mackay with typically less runoff during December and associated with its track, speed, areal extent region contains some of Australia’s Basin and the Sandy Desert Basin which contains April (WAPC, 2009). Mean annual runoff rates and saturation of catchments from prior rainfall. consistently hottest places with highly extensive areas of salt lake chains. The Pilbara from the major rivers in the Pilbara region Indeed rainfall totals in excess of 100 mm are irregular rainfall, where the average Surface Water Area, which covers the western typically represent 2.5% to over 10% of the common with tropical lows that move over land. half of the Pilbara, is proclaimed under the annual rainfall. In February 1997 a slow moving low moved yearly evaporation (approximately Rights in Water and Irrigation Act 1914 for the over the west Kimberley, Pilbara and Gascoyne Open cut mining in the Pilbara results in the 3,000mm) exceeds average yearly purposes of regulating the taking of water from causing rainfall in excess of 400 mm in parts creation of massive voids, such as the BHP rainfall. This climate, which can watercourses and wetlands. and one of the highest ever floods along the Billiton-owned pit at Mount Whaleback near Ashburton River. Cyclone Joan in December 1975 result in severe droughts and major Stream flows in the Pilbara region are mostly a Newman. Acid rock drainage was not originally caused over 400 mm of rain near its track, the floods simultaneously occurring direct response to rainfall, and as such they are considered a serious concern in the Pilbara due highest fall being 591 mm at Marandoo (BoM highly seasonal and variable. With the exception to the low rainfall and high evaporation rates over the region, supports a unique 2012a). and rich landscape of biodiversity of some small but important, spring-fed sections, experienced in the region. However, acidic all waterways in the region are ephemeral, in runoff was detected from a storage area at Flooding is enhanced when multiple tropical and water resources, which include that surface flow ceases for at least part of each Mount Whaleback in 1995, following the heavy lows occur within a few weeks of each other. many waterways, wetlands and year. The major rivers of the region (in order of rains resulting from Cyclone Bobby (Johnson During January and February 1961 rainfall totals groundwater resources. highest to lowest mean annual flow) are the De and Wright, 2001). The acid rock drainage was exceeded 200 mm during two tropical cyclones. Grey, Ashburton, Fortescue, Yule, Sherlock, Cane, caused by the oxidation of highly reactive pyritic At Wittenoom it was described as the worst 5.1.1 Waterways Robe, Harding, Maitland and Turner (DoW, 2000) shale, which forms acid after lengthy exposure flood in memory as water levels rose to 23 m in As a result of irregular rainfall patterns and (Figure 36). to air, water and bacteria. Acid contamination sections of the Gorge. In both events Wittenoom of groundwater and surface has the potential to was isolated. In 1980 cyclones Amy, Dean and extreme climatic conditions, rivers in the Pilbara The largest rivers in the region, the De Grey, result in the degradation or loss of wetland and Enid moved over the eastern Pilbara causing are subject to massive variations in flow. These Fortescue and Ashburton rivers flow for associated vegetation, and habitats. total rainfall to exceed 600 mm in some areas conditions result in a landscape with wide significantly greater periods of time than the (BoM 2012a). floodplains which allow the periodic passage other rivers, however, in wetter years only the Management of acid rock drainage has improved of large volumes of water and sediment across Fortescue River flows for more than half the in the Pilbara since and current management Episodic flooding is a natural hydrologic feature the tablelands to the coastal areas and near- year. The major rivers discharge towards the methods involve covering highly reactive and of the Pilbara region which provides critical shore marine environment, particularly during Indian Ocean over the coastal plains, contributing potential acid-producing materials with inert recharge of groundwater aquifers and inundation cyclonic events. significant recharge to groundwater resources backfill material or water. of waterways and wetlands that may have been The Department of Water identifies five major in the process, such as the Millstream aquifer. dry for extended periods causing explosive Flooding drainage basins within the Pilbara (DoW, 2000). River flowpaths are often wide and intertwining ecological responses which are a remarkable These are the Ashburton River, Onslow Coast, and discharge points are usually a combination Heavy rainfall and associated river flooding is feature of the region. Fortescue River, Port Hedland Coast and De Grey of direct ocean channels and dispersal through the main impact for most cyclone events in the River (Figure 36), which drain the rocky outcrops marshy flats. inland Pilbara. The highest rainfall is usually found along or just east of the track for most 80 Pilbara state of the environment rePort 2013 PIlbara state OF THE ENvironment report 2013 81 FIGuRE 36 Surface water resources ©2012 While Essential Environment has taken care to ensure the accuracy of this product, Essential Environment make no representable or wannties about its accuracy, completeness or suitability for any particular purpose. Essential Environment and client cannot accept liability of any kind (whether in contract, tort or otherwise) for any expenses, losses, damages and/or costs (including indirect or consequential damage) which are or may be incurred as a result of the product being inaccurate, incomplete 82 or unsuitable in any way and for any reason. Datasource: landgate, Geoscience Australia. Created by H. Brookes Projection: MGA50:zone50 FIGuRE 37 Groundwater resources ©2012 While Essential Environment has taken care to ensure the accuracy of this product, Essential Environment make no representable or wannties about its accuracy, completeness or suitability for any particular purpose. Essential Environment and client cannot accept liability of any kind (whether in contract, tort or otherwise) for any expenses, losses, damages and/or costs (including indirect or consequential damage) which are or may be incurred as a result of the product being inaccurate, incomplete or unsuitable in any way and for any reason. Datasource: landgate, Geoscience Australia. Created by H. Brookes Projection: MGA50:zone50 83 5.1.2 Wetlands and reliability of groundwater resources depends Table 2: Water availability, allocation limits & levels of management risk of major aquifers in the Pilbara The Pilbara has a variety of seasonal, intermittent on the different aquifer types, thus impacts of and permanent wetlands, a number of which abstraction from aquifers also vary. Aquifer Allocation limit Water available levels of risk (kl/year) management^ are considered to have important ecological Groundwater is most easily located and accessed significance (Figure 36). Eighty Mile Beach near surface water drainage lines or alluvial lower Cane alluvial 1,000,000 Water available Medium coastal wetland system is the only internationally channels. Aquifers in coastal areas of the Pilbara lower Fortescue alluvial 6,600,000 Fully allocated low recognised Ramsar site in the Pilbara, which are considered small, receiving a typical annual contains the Mandora Salt Marsh. The Millstream lower Robe alluvial 5,090,000 Water available low recharge of less than 10 Gl/year (DoW, 2010b). pools and the Fortescue Marsh are currently Millstream** 15,000,000 Over allocated High proposed Ramsar sites (DoW, 2010b). There are Groundwater management areas may be lower De Grey alluvial 10,150,000 Fully allocated High also a number of nationally important wetlands in proclaimed under the Rights in Water and the Pilbara, including the De Grey River wetland Irrigation Act 1914. The western half of the lower Turner alluvial 420,000 limited water low system, Fortescue Mashes, Karijini (Hamersley Pilbara region is covered by the proclaimed lower Yule alluvial 10,560,000 Fully allocated High Range) Gorges, leslie (Port Hedland) Saltfields Pilbara Groundwater Area, with the remainder Broome* 10,000,000 Water available low System, Millstream Pools, lake Disappointment covered by the proclaimed Canning-Kimberley (Savory Creek) System, Yadjyugga Claypan, Groundwater Area.

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