Next Article in Journal
Evaluation of the Mechanical Behavior of Asphaltic Mixtures Utilizing Waste of the Processing of Iron Ore
Next Article in Special Issue
New Accountability Approach: Utilising Dynamic Zero-Waste Baselines to Mitigate Water Wastage in Gold Mines
Previous Article in Journal
Physical and Numerical Modeling of a Flow Control Layer Made with a Sludge and Slag Mixture for Use in Waste Rock Pile Reclamation
Previous Article in Special Issue
Examining Sustainable Transition and Post-Mining Management in the Ruhr Region and the Prospective Evaluation of Knowledge Transfer to Kosovo’s Mining Sector
 
 
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Review

Below Water Table Mining, Pit Lake Formation, and Management Considerations for the Pilbara Mining Region of Western Australia

by
Cherie D. McCullough
Mine Lakes Consulting Pty Ltd., Perth 6919, Australia
Mining 2024, 4(4), 863-888; https://doi.org/10.3390/mining4040048
Submission received: 6 September 2024 / Revised: 2 October 2024 / Accepted: 10 October 2024 / Published: 17 October 2024
(This article belongs to the Special Issue Post-Mining Management)

Abstract

Located in northern Western Australia, the Pilbara is the highest productivity region for iron ore and other metal mining in Australia. As elsewhere, mine closure guidelines typically require post-closure landforms to be safe, stable, non-polluting and sustainable here in the long-term. I reviewed the primary literature, including international, national and state government guidelines and regional case studies for mine closure and related socio-environmental topics, to understand the key risks and management strategies needed to achieve these broad expectations for below water table (BWT) mining. Many BWT open cut mining projects will result in pit lakes in this region, many of which will be very large and will degrade in water quality with increasing salinisation over time. As an arid region, risks are dominated by alterations to hydrology and hydrogeology of largely unmodified natural waterways and freshwater aquifers. Although remote, social risks may also present, especially in terms of impacts to groundwater values. This remoteness also decreases the potential for realising practicable development of post-mining land uses for pit lakes. Explicitly considered risk-based decisions should determine closure outcomes for BWT voids, and when pit backfill to prevent pit lake formation will be warranted. However, maintaining an open pit lake or backfilling a void should also be considered against the balance of potential risks and opportunities.

1. Introduction

As for most mature mining jurisdictions, mine closure guidelines in Western Australia require post-closure landforms to be physically safe, geotechnically stable, geochemically non-polluting, and sustainable in the long-term [1,2]. Jurisdiction-specific guidelines usually depend on site-specific characteristics, and stakeholder values, such as long-term end uses for the water resource, as well as accounting for regional water quality and ecological tolerances and any pre-existing disturbances. However, all pit closure planning requires the development of closure objectives/outcomes and associated completion/success criteria to demonstrate achievement of these [3,4]. For instance, although pit lakes are novel ecosystems not previously present in the landscape [5], they must still meet a water quality standard that does not present an unacceptable risk to receptors (e.g., human, livestock, and ecological uses) and the broader environment [6,7,8]. Pit lakes are further increasingly expected to demonstrate consideration of, if not also provide, opportunity as a post-mining land use (PMLU) [9,10,11,12,13].
I reviewed the primary literature, including international, national and state government guidelines and regional case studies for mine closure and related socio-environmental topics, to understand the key risks and management strategies needed to achieve these broad expectations for below water table (BWT) mining. The review prioritised peer reviewed journals. To this end, Google Scholar searches were made using the key words “Pilbara”, “mining”, “mine”, “pit lakes”, “mine lakes”, and “closure planning”. Due to recent substantial changes in the scale of mining in the Pilbara, I also strove to source information from articles from after the year 2000. I supplemented journal articles with conference proceedings, which were also used due to the paucity of the primary literature on mining in the Pilbara, especially those from the regular industry conferences “Australian Acid and Metalliferous Drainage (AMD) Workshop, “Mine Closure”, “Life of Mine”, “International Mine Water Association (IMWA)”, and the “International Conference on Acid Rock Drainage (ICARD)”.

Below Water Table Mining

The large and numerous current and proposed mines of the Pilbara region of Western Australia (WA) are forecast to increasingly extend into deposits below the water table (BWT). Mining BWT often requires extensive dewatering to access ore, and not all pits can be backfilled to prevent pit lakes forming due to the availability of materials and cost [14]. Upon cessation of mining, dewatering ceases and the water table recovers to a post-mining level that is expected to develop into a pit lake. Climate is the most important factor of the hydrologic processes associated with a pit lake [15]. In general, surface hydrologic processes (e.g., direct precipitation, evaporation, and surface water runoff, including occasional stream or river inflows) are defined by the regional climate and interact with groundwater processes to form a simple water balance budget for the pit lake.
Following groundwater rebound and dissolution of the cone of depression, the pit lake begins to fill with water and groundwater inflow into the pit initially increases as the inflow area increases. Later, groundwater seepage into a pit slows as the change in the pressure head decreases [16]. As a result, total inflow into a pit lake is expected to gradually decrease as the open pit fills, while total outflow is expected to increase due to increased evaporation from the greater surface area of the pit lake area. At some stage, total inflow approximates total outflow and the water level in an open pit will reach equilibrium, albeit responding dynamically to changes in seasonal precipitation and evaporation rates. Water level fluctuations may occur, e.g., due to occasional cyclones and associated surface water inflows. Groundwater inflows are generated from precipitation recharge and tend to buffer short-term climatic changes, but long-term climatic changes will be reflected in groundwater inflows.

2. Pilbara Context

The Pilbara region is defined variously under different purposes but is located in Western Australia, 1200 km north of Perth, and extends over some 300,000 km2 (Figure 1). The region is almost exclusively Crown land, with freehold land generally concentrated along the coastline [17]. Predominant land uses are mining and pastoral, although the areas to the north and north-east of the Pilbara are too dry to support the grazing of livestock and include few settlements. Three national parks have also been proclaimed in the region.

2.1. Climate

The Pilbara region consists of a climate classified as an arid hot desert (BWh) by the Köppen–Geiger system [18]. Very hot summers (up to 50 °C) last from October to April and mild to cool winters (near 0 °C) occur from May to September. Summer rainfall occurs from either tropical cyclones or thunderstorms, while winter rainfall is typically from low pressure trough systems [19]. Average annual rainfall in this highly active mining region is low while evaporation can be very high [20]. Monthly evaporation also significantly exceeds rainfall throughout the year and seasonally ranges from around 150–200 mm per month during the dry season, and up to 450 mm in December and January during the wet season.
Sporadic and intense thunderstorms are typical for the region from January to March, and an annual average of two tropical cyclones make landfall, resulting in daily rainfall amounts of up to 200 mm over a 24 period [21]. Flooding is enhanced when multiple tropical lows occur within a few weeks of each other [22].

2.2. Geology

The Pilbara includes a wide variety of ancient sedimentary and metamorphic rocks [23]. The iron ore deposits for which the region is perhaps best known have mostly been developed by later, local enrichment of sedimentary banded iron formations.
In the Pilbara region, iron ore is mined from three major stratigraphic entities, namely the Turee Creek Group, the Hammersley Group (the mineralised banded iron formation of the Hamersley Group and the Brockman or Marra Mamba iron formations) and the Fortescue Group, or from eroded and redeposited material, e.g., channel iron deposits. Much mining may be considered an essentially benign activity from a geochemical perspective, not least because the ironstones are mined at shallow depth and from natural exposures over large parts of the ancient terrain [24].
Most deposits are ore bodies that existed under reducing conditions but with a genesis not related to sulphide mineralisation. Supergene-enriched banded iron formation (BIF) or detritals that are above the water table and have been exposed to long term weathering are unlikely to contain sulphides within the ore. However, sulphide-bearing shale or lignite may be inter-bedded with or lie stratigraphically below the ore body.
The local geology of each deposit varies; however, the most problematic formations with potentially acid-forming rocks are considered to be the black shale units, such as those found in the Mount McRae Shale (MCS) and Brockman Iron and Marra Mamba Iron Formations which present, to some extent, at most mine sites in the region [25]. Owing to the discreet occurrence of lignite in the region, little is presently known about its geochemical properties [26]. The MCS hosts mostly black shale, and it is overlain by the Dales Gorge Member of the Brockman Iron Formation, which is often exposed in pits where the lower portion of Dales Gorge Member is mined. MCS if unoxidised, is known to contain pyrite. Both lignite and shale lithologies are known to host sulphide mineralisation when unoxidised [27].

2.3. Mining

Mining in the Pilbara region dates back more than 100 years to the discovery of gold at several localities, and the proclamation of the Pilbara Goldfield in 1888. Today, the Pilbara region produces a substantial proportion of the value of mine products in WA, being host to the largest iron ore deposits in the world, which are the predominant economic product of the region [24].
The Goldsworthy iron ore deposit (Figure 2) was initially discovered by the then Mines Department in the 1950s, and mine production commenced at Mt Goldsworthy in 1962 [23]. Identification of many of the present-day mining operations soon followed, with the discovery of iron ore deposits at Mt Tom Price in 1962 closely followed by the Mt Whaleback, Pannawonica, and Paraburdoo orebodies. Further substantial mine developments since the late 1980s, including the commencement of mining at Jimblebar, Channar, Marillana Creek, Marandoo and Brockman No 2 Detritals, and Yandicoogina.

2.4. Ecology

The Pilbara region in remote north-western Western Australia is one of the oldest land surfaces on Earth. With a diversity of geography from ancient and vast sand deserts to the north and east, and highly metamorphosed rocks to the south, it has long been regarded as one of Australia’s centres of biological diversity, endemism, and refugia [28]. The region is an area of exceptionally high biotic diversity and endemism and harbours taxa genetically distinct from neighbouring regions, despite close geographical proximity of populations [29]. This is especially so at the eastern and southern margins, where habitat gradients are pronounced. Genetic divisions may also relate to major drainage divides and geological discontinuities associated with eastern and western Pilbara terrains. The Pilbara landscape supports one of the richest reptile assemblages in the world [30]. Although no mammal species are endemic to the Pilbara bioregion, it is also home to some of Australia’s most charismatic vertebrate species, including the northern quoll (Dasyurus hallucatus), mulgara (Dasycercus spp.), and greater bilby (Macrotis lagotis).

2.5. Mining Below the Water Table in the Pilbara

Across all commodities, there were already more than 2000 mine voids and more than 150 mines operating BWT in Western Australia early in the millennium. Many were located in the Pilbara and Goldfields regions [31]. Approximately three quarters of Pilbara iron ore resources were already located BWT [23]. There are now an estimated 670 open pits in the Pilbara that have the potential to become pit lakes in the future [17] (Figure 2). The final dimensions of the Whaleback Mine, the world’s largest iron ore mine, will measure 5.5 km long, 1.5 km wide, and 500 m deep [32], and is expected to form a pit lake [33]. Consequently, the major issue for the Pilbara arid iron ore mines continues to be the potential impact of mines which extend BWT on regional groundwater quality [34].
Pilbara pit lakes are typically either ‘throughflow’ lakes or terminal sinks [31,35,36]. Often due to their location transecting dynamic groundwater systems, throughflow lakes both have groundwater inflows, then seep pit lake waters back into regional aquifers. In areas of net evaporation, like the Pilbara, pit lake evaporation rates often exceed water inflow rates, causing the pit lake to function as a hydraulic ‘terminal sink’ [36]. If the steady-state pit lake elevation stabilises below the surrounding pre-mining groundwater level, the pit lake then becomes a terminal sink, with no water released into the environment through seepage into the groundwater system, although a terminal pit lake may still discharge to ground and even surface waters during extreme rainfall events where freeboard is insufficient to retain flood flows to the pit void.
Some Pilbara pit lake types can also occasionally act as ‘flowthrough’ (sensu [37,38]), by receiving, and then discharging, local surface waters during episodic events, such as storms, or where a pit intercepts a floodplain. For instance, a ‘terminal sink’ pit lake may still overflow during extreme rainfall events where the freeboard is insufficient to retain flood flows to the pit void.

2.5.1. Water Quality

Although salinity typically increases closer to the coast, in general, the iron ores of the Pilbara form good aquifers with potable or near-potable water quality, barring often high concentrations of nitrate [39,40]. However, acid and metalliferous drainage (AMD) may be generated following the disturbance of these geologies, increasing solute concentrations and decreasing the pH of the water it contacts [41]. AMD arises predominantly from the oxidation of pyrite, FeS2, present within carbonaceous shale units interbedded with the sedimentary ironstone, and as localised secondary mineralisation. Disseminated pyrite and secondary pyritic veining may also be abundant in lignite occurring locally in the overburden. The precise chemical character of the AMD, and, thus, the potential pollution risk to the environment, differs from that generated by other types of mining. While pyrite oxidation can generate highly acidic, low pH, sulphate- and iron-rich solutions, characteristic of AMD, the dissolved metal(loid) concentrations are generally neither as elevated, nor as varied, as in drainage formed during the mining of other commodity types. AMD associated with Pilbara iron ore mining is found to have traits similar to those of coal deposits, where biophile elements, such as the metalloids arsenic and selenium, and the metals mercury and cadmium, are notable contaminants of potential concern (COPCs) [27].
The chemogenesis of a pit lake is a function of many geochemical processes that can occur within a pit lake. Each of these processes contributes to long-term pit lake water quality. Reactions within the damaged rock zone surrounding the pits can occur from blasting and other impacts. The damaged rock zone of a pit lake includes the shell of highly fractured rock or sediment around the pit perimeter and also talus at the base. Mineral reactions, but especially dissolution of soluble mineral phases, will result in the addition of some trace elements and particularly salts, to pit wall runoff in all pit lake water balance types. The water quality of terminal sink lakes is expected to show increased metal(loid) and salt concentrations over time as solutes introduced through groundwater inflow and pit wall runoff are concentrated by evaporation [42]. However, both through-low or flowthrough water balances can lead to solute mass loss from the pit.
Groundwater inflows are the major contributor to the water quality of Pilbara pit lakes. Mass loading associated with groundwater solutes directly affects pit lake water quality [43], and groundwater flow to the pit lake will comprise the largest water volume inflow. Groundwater inflow volumes will also affect the residence time of the pit lake, which in turn can affect water quality. Sulphidic material in the cone of depression created by dewatering the orebody, and the hydraulic conductivity of this material can also influence groundwater quality as the water table recovers [44]. As groundwater levels rebound, oxidation products will dissolve in the inundating groundwater [45]. Seasonal fluctuations in lake levels will affect weathering process due to the continual re-exposure and oxidation of exposed lithologies [46]. Concomitantly, groundwater with high alkalinity can contribute to increasing the pH of a pit lake or buffering potential acidic drainage flowing from the lake.
Highly elevated nitrate concentrations can also occur in some regional aquifers, e.g., deep groundwaters in Australian Pilbara mining region [31,33] and are common to mine waters through blasting residues [47,48]. Nitrate toxicity is increasingly recognised as a threat to aquatic ecosystems, [49] and particularly those receiving mine waters [50], although local differences in ecological tolerances may exist in these areas also [51]. As such, nitrate is an emerging risk for even neutral pit lake water quality, especially during early years of development [52].
The generation of relatively dense, saline water at depth and periodic addition of fresh rainwater to pit lakes can result in a salinity stratified (monomictic) lake [53,54,55] or with sufficient flows can form a mixed (holomictic) freshwater pit lake [56]. If the pit lake has not mixed and remains stratified, it is likely that the water quality discharging from overtopping of the pit will be similar to site run off (Figure 3). The natural flooding of mine voids from intense rainfall events demonstrates the viability, on an opportunistic basis, of final voids as potential surface-water reservoirs [31].
Mixing of the pit lake during turnover can contribute to processes that may affect lake chemistry, such as the vertical homogenisation of dissolved chemical parameters, the vertical distribution of dissolved oxygen stored in the epilimnion, sediment re-suspension and vertical distribution of carbon dioxide stored in the hypolimnion followed by ex-solution at the lake surface [43]. Annual seasonal mixing of the entire water column is likely in even steep-sided pit lakes of Australia’s tropical north [57,58].

2.5.2. AMD

Modelling of sulphide oxidation has shown that the relative contributions to sulphate production may vary by about five orders of magnitude, with oxidation continuing until all sulphides are consumed or until reactive geologies are inundated. The indicative relative magnitudes are as follows [45]:
  • Talus (1);
  • Blast damage fractures adjacent to the pit wall (0.01);
  • Pit wall surface (smooth) (0.0001);
  • Pit wall surface (rough surface contribution) (0.0001), and;
  • Non-blast damage fractures behind the MCS (0.00001).
Some geologies, although low in sulphur, may contain relatively geologically elevated concentrations of metals and metalloids, such as As, Se, Sn, and Mn [59]. Natural waters that contact these enriched geological materials may accumulate higher concentrations of solutes when compared with default water quality assessment criteria [60]. The mineralogical hosts for these elements will determine their long-term leachability [59] as many trace elements are partly or entirely bound within relatively unreactive minerals, such as crystalline silicates or iron oxides. However, some trace elements associate with more soluble mineral components, such as the following:
  • Soluble sulphates and carbonates, as sources of transition metals, alkaline earths, uranium, and selenium;
  • Manganese oxyhydroxides as sources of barium, transition metals, and thallium.
Oxidisable components are likely to be the principal contributors to long-term leaching from low sulphur wastes, e.g., trace sulphides, carbonaceous material, and redox-sensitive elements adsorbed on mineral surfaces. Nevertheless, only a minor proportion of the total trace element mass is usually soluble, and these leachable masses are unlikely to be of environmental significance compared to high sulphur materials. Low sulphur wastes, therefore, generally pose a negligible risk of AMD.
Mineral precipitation of trace elements may also be important as pit lake salinities increase. Dissolved mineral phases may precipitate from mixed pit lake waters, which can reduce the concentrations of some chemical parameters and provide surfaces for metal adsorption. Moreover, metal adsorption of metals to hydroxide precipitate surfaces, clay minerals, or organic material with reactive surfaces in solution can decrease concentrations of metals and metalloids. These processes might be very important where pit void shells and backfill materials present significant surface areas of iron hydroxides in particular. Speciation and redox processes of anions and metals in solution can be influenced by geochemical processes that occur within the pit lake. However, due to the pit lakes being largely mixed throughout time, the regular transformation of one species to another through oxidation or reduction reactions, precipitation or dissolution of mineral precipitates, or desorption/adsorption onto surfaces is unlikely.
Prior to the development by a new mining project, many sites may not have water quality conditions defined as default by ANZG [60] water quality guidelines (95% freshwater aquatic ecosystem biodiversity protection). An increase in contaminant concentrations is reasonably expected where the geochemistry of a site is already elevated for certain elements and characteristics that make this region of interest for mineral extraction. Defining water quality completion for closure is, therefore, more than just using generic national guidelines, but an explicit consideration of the baseline regional bio-physico-chemical context [61].

2.5.3. Salinisation

Although not a direct COPC in itself, elevated concentrations of conservative solutes, such as Ca, Na, and Cl, can present as salinity. At any time after the cessation of mining, the total solute load in the pit void is the cumulative sum of (i) the solute introduced by in-flowing groundwater, and (ii) reaction products mobilised and introduced to the pit void. Elevated major ion concentrations are recognised as being a key contributor to the toxicity of many mine waste waters. However, specific major ions do not clearly drive the toxicity of saline seepage waters, and the effects are probably due to total salinity [62].
The groundwater beneath the Fortescue Marsh is hypersaline (approximately 3–4 times the salinity concentration of sea water), but fresh to brackish in mining areas [63]. Generally, the EC measurements of in situ geological samples indicate they are not naturally saline, with the majority of EC measurements below 0.4 dS/cm [64].
However, the climate in the Pilbara is characterised by hot summers with periodic heavy rain and mild winters with occasional rain, which means that the periods between dissolution events may be long, and the volumes of water involved may be low; contact waters are, therefore, often saline [65], especially for secondary oxidation products [66].
The rate of salinisation of the pit lake is dependent upon the surface area exposed to evaporation, such that larger lake area will have greater evaporation rates [67]. Given the clear skies and high temperatures experienced in the Pilbara, the solar radiation input (and resultant evaporation rates) are very high throughout the year [68].
In increasing order of importance, short-term sources of salinity to Pilbara pit lakes are expected from the following (Figure 4):
  • Direct rainfall;
  • Catchment inflows;
  • Pit shell exposures and talus;
  • Groundwater inflows;
  • Waste materials within catchment (including backfill).
Long-term, groundwater solutes are expected to dominate.
A major challenge for closure planning at BWT mining operations is predicting and managing evaporation from final void pit lakes, especially where pit lakes can impact on downstream groundwater and surface water flows and quality [69]. Long-term degradation of regional groundwater quality can be caused by seepage of poor pit lake water quality that can extend as plumes for many kilometres down-gradient [70], including for salinity [71]. The time taken for water in large voids to become highly saline is estimated in the order of centuries. Consequently, seepage rates are likely to be from metres to tens of metres per year, such that environmental impacts many kilometres away from the pit lake may not occur for more than one thousand years.
A closure approach that is increasingly being adopted is to infill the final voids with waste rock to above the pre-mining water table to prevent the development of a permanent pit lake and subsequent evaporative losses. However, with a stripping ratio of less than one for iron ore mines, there is typically insufficient waste rock to infill all mine areas to above the pre-mining water table. Instead, integration of hydrogeological modelling with mine planning can advise the selective infilling of pits, largely using run-of-mine waste dumping, and some diversion of surface water flows [69]. Diversion of some minor creek tributary flows into specific locations within the mine path may also induce hydraulic gradients that maintain aquifer throughflow and water quality.

2.5.4. Long-Term Water Quality

The long-term water quality of pit lakes plays a key role in mine closure considerations [72], and Western Australian pit lake closure planning and management needs to predict changes in water quality of any planned pit lake over time [73]. Potential deleterious impacts to water quality that require consideration include acidity, metalliferous, and saline effects, while the potential for pit lake stratification also plays an important role.
Factors that control the long-term evolution of water quality include local geology, hydrogeological and climatic conditions [74]. Although initially influenced by pit shell solutes dissolution, the water quality of Pilbara pit lakes will be predominantly controlled first by the following factors (Figure 5):
  • Groundwater inflow quality;
  • Evapoconcentration of this groundwater contribution to the total pit lake volume.
Direct precipitation on the lake surface can result in the dilution of dissolved constituents. Conversely, evaporation continually increases concentrations of salinity and other solutes. However, evaporation rates exceed rainfall and, therefore, rainfall has a minor dilution effect unless it is an extreme event. Consequently, water quality trends are primarily due to processes of groundwater inflow solutes being evapoconcentrated and the seepage of pit lake water to regional aquifers, flushing out solutes. The water quality of terminal sink lakes is, therefore, expected to deteriorate over time due to evaporation [75,76]. Since Pilbara pit lakes have little or no attenuation of salinity, this poor water quality is unlikely to be resolved naturally, even over long time scales (McCullough, 2008).

3. Risks

BWT lakes can present risks to humans, livestock, and wildlife from mine closure into perpetuity. The key risks and their causes are described below.

3.1. Creek Capture

The heavy, intense rainfall and subsequent flood events experienced in the Pilbara makes climatic factors a key influence on the stability of closure landforms. Iron ore mines in the Pilbara region operate in an environment with ephemeral creeks that are subject to flash flooding events following rainfall, predominantly during the wet season. Streamflow in the smaller flow channels is typically short in duration and ceases soon after rainfall passes [77]. However, runoff can persist for weeks in the larger river channels, which drain the larger catchment following major rainfall events resulting from tropical cyclones.
The closure implications of pits, waste dumps, and land bridges in relation to the creeks, and surface water flows and subsequent flood events, are better understood today than when many old Pilbara BWT mines were begun in the late 20th century when, globally, smaller watercourses were historically allowed to flow into mining pits. This practice has been recognised as a risk to surface water management, and diversion and complete reinstatement are now used to protect even smaller river channels [78,79].
However, river diversion (or river relocation) remains an issue for mine closure and rehabilitation [79] and historical mine footprints can often present significant closure challenges, with pits, waste dumps and land bridges often located adjacent to, or even within, creeklines and their floodplains. Creek capture to pit voids can occur during or following extreme rainfall events, especially where the track of these cyclones is in close enough proximity to cause heavy rains within the catchment and significant creek flows through the mine site. Without engineered surface water management structures, a natural watercourse can then scour a path into a mine void, effectively terminating downstream flow in a pit lake.
A risk-based approach can help determine which flood magnitude different pit lake and associated catchment designs meet [22]. Analysis of flood depth data from an inundation map can show predicted flood depths across the post-mining landscape and which pit lakes are predicted to intercept creek flows in the absence of further mitigation measures.
Although complete operational backfill is rarely available for low waste to ore strip ratio for iron ore mines [80], backfilling selected pits adjacent to creek lines during mine operations can manage the flood closure risk [22]. Creeks can also sometimes be reinstated over the pit and backfilled with detrital mine waste, adopting a similar length and grade to the original where hydraulic modelling shows catchment flows are of short duration with minor infiltration losses to backfill [77]. In these cases, drainage features can be re-establish over fully backfilled pits, partial pit backfill with land bridges to convey sediment and flows, and total or partial hydrologic disconnection between partially-filled open pits and the channel system [81]. Operational works can be used to reduce the associated earthmoving costs at closure and the overall disturbance footprint can be reduced with the placement of a waste in-pit and some waste landforms not being required.
Although well-engineered diversions can require less maintenance and demonstrate functioning similar to a natural systems, [82], the poor condition of river diversion channels can prevent mining companies from relinquishing their mine to the government after mining has ceased. Many regions lack guidance for designing river diversions from appropriate geomorphic and hydraulic analogue conditions. However, establishing baseline geomorphic reference criteria for unmodified catchments can guide restoration efforts to allow recovery and ensure the stability of the fluvial system [79].

3.2. Impact of Groundwater Loss

Pilbara surface water is scarce and shows high seasonality. As such, groundwater has become a strategic resource in the Pilbara region for ecological communities [39], and groundwater-dependent ecosystems (GDEs) are often highly reliant upon high-quality groundwater systems.
A significant risk from mine pit lakes occurs when there is a hydrogeological connection between the mine voids and important wetlands, waterways, or groundwater resources. Local groundwater level depression can occur where groundwater flow occurs in perpetuity with net evaporative pit lake water balances [69,83,84,85]. Projects involving extensive groundwater drawdown (sometimes through the interaction of dewatering operations at adjacent projects) have the potential to affect a large proportion of the population of a restricted species or to threaten the persistence of species with particularly small ranges [86].
Flora recorded from around the pit lakes generally comprise drought-tolerant plant taxa with no reliance on groundwater for survival, e.g., hummock grasslands, low tree steppe over spinifex, and low woodland. However, the dominant tree species of the surrounding creek line riparian zones are Eucalyptus camaldulensis ssp. refulgens (River Red Gum), Eucalyptus victrix (Coolibah), and Melaleuca argentea (silver cadjeput). A fourth, Sesbania formosa, while less widespread, is also a relevant species in Pilbara riparian systems. Although there have been few studies, the presence of these species is often used to infer the presence of a groundwater-dependent ecosystem (GDE), granted that dependency within species has been shown to vary both spatially and temporally [87]. Interactions between salinity and water level are also largely unknown [88].
Obligate phreatophytes are those species for which access to groundwater is critically important, and they can only inhabit areas where they have access to groundwater for at least some proportion of their environmental water requirements. Conversely, facultative phreatophytes are plant species for which access to groundwater is not necessarily important to their presence. E. camaldulensis and M. argentea are large, deep-rooted trees which occur along waterways where the water table is typically <5 m below the surface in tropical north Australia [89,90]. Although it does not form the only source of plant water use [91], groundwater is a critically important component of these species’ environmental water requirement. In particular, M. argentea is an obligate phreatophyte associated with shallow groundwater and/or permanent pools of surface water at points along the creek. While not a true phreatophyte, E. victrix is not dependent upon groundwater and is relatively drought tolerant, but it is likely to exhibit signs of stress with decreased access to groundwater [89,92].
Pilbara fractured rock and coarse alluvial aquifers also support diverse faunas comprising obligate groundwater inhabitants, largely crustaceans but also including insects, worms, gastropods, mites, and fish of typically short-range endemics, with the richest known groundwater and cave-dwelling faunal diversity in Australia having over 1000 species [93]. Although this subterranean fauna remains poorly understood, it is apparent that these numbers are globally significant. Taxonomic resolution among some groups of stygofauna is poor, and species richness is likely to have been substantially underestimated [86].
Although mining development has often occurred in areas that have a high value for subterranean fauna diversity, impact assessments suggest relatively modest impacts on long-term persistence for this component of biodiversity [94]. However, as few mines in the Pilbara have closed, little information is available on actual impacts [17]. In addition to localities where groundwater depression may threaten riparian and other GDEs, the Pilbara contains mining regions with concentrations of mine voids which pose a future cumulative risk to the environment [17].

3.3. Direct Contact and Drinking

The Pilbara region, whilst arid and relatively isolated, hosts a diversity of ecosystems that may be susceptible to COPC toxicity [24]. There are numerous priority ecological communities (PECs) and threatened ecological communities (TECs) which constitute environmental receptors; the relative paucity of both permanent surface freshwater sources and groundwater of useable quality makes the ecological systems based on these water resources especially sensitive to contamination. Much emphasis is placed on protecting GDEs, which include riparian vegetation communities and subterranean fauna.
Environmental receptors can make direct contact with pit lake waters, either through active movement toward the lake, or through passively receiving pit lake waters into their receiving environments (surface or groundwater). Pit lakes and other smaller water bodies created by mining are frequently used by wildlife [95]. These biota include birds [9] (such as long-distance migratory species [96]) and also bats [97]. Contact can lead to toxicity that is either lethal to individuals (acute) or sub-lethal chronic (has an impact on populations). Prolonged contact with contaminated pit lake water may cause skin disorders, like dermatitis [98]. Direct contact may also cause include impacts on fauna or human health through ingestion by drinking if void water becomes unpotable and is consumed [9].
Some Australian animals minimise water loss to such an extent that they meet all their water needs from the water content of their food and from metabolic water alone [99]. In particular, Australian marsupials demonstrate much lower water requirements than introduced mammal pest species [100]. Even native mammals, such as dingo (Canis lupus dingo), are adapted to infrequent drinking [101]. As a result, water requirements from Australian native mammals in the region are not expected to be high, and native terrestrial mammals are not expected to drink frequently from pit lakes. However, saline water provides limited food and no drinking water resources, and does not likely function as a significant habitat for many receptors [102,103]. Nevertheless, there are expected to still be many pathways from pit waters to environmental receptors under freshwater conditions, as presented in other papers [104,105,106].

3.4. Discharge to Waterways

In general, fluvial processes in the Pilbara, located in the arid subtropics, tend to be driven by infrequent, high intensity, and short duration hydrologic events that are related to the occurrence of tropical cyclones [107]. Regional waterways are ephemeral and, therefore, only support occasional and limited ecological values when flowing. Recharge to the groundwater system is thought to be dominated by flows in these ephemeral creeks [67]. However, where perennial river pools are present, they are connected to and interact with the underlying alluvial aquifer [108]. Aquatic invertebrates show high diversity for an arid zone, with about one-fifth of all species encountered currently believed to be endemic to the region [109], reflecting the abundance of consistently fresh, permanent water maintained by freshwater aquifers. Seedling recruitment and subsequent growth also mainly depend on heavy rainfall flooding events [110], which are likely to coincide with pit lake discharge [37,111].
Understanding pit lake discharge risk requires a good understanding of what frequency and conditions discharge might occur under. Stochastic water balance modelling will generally effectively advise risk likelihood. If discharge does occur, pit lake water quality, and the nature of the receiving systems downstream, will provide information on the consequences of decant risk. A freeboard should be maintained such that the discharge is not likely under predefined rainfall events, in-turn determined as a consequence of discharge [37].
Model performance has been shown to be dependent on the representativeness of meteorological observations; observations for modelling applications can be undertaken using either regional parameters from case studies [112] or, preferably, on site at the pit lake level [68]. A greater frequency of intense rainfall events is expected by both modelling for the region [113] and empirical evidence [114]. This short-term greater net precipitation can increase the risk of water outflows from pit lakes to both surface and groundwaters [115], even in arid regions [36,116]. Climate change can also increase the rates of pit lake hyper-salinisation and the associated risks through higher mean temperatures. Pit lake water balance and water quality modelling should consider expected changes to storm events under climate change [117].

3.5. Seepage to Groundwater

Backfill to prevent evaporative losses of groundwater through pit lakes may include mineralised and non-mineralised waste rock (Figure 6). This solution can result in the maintenance of adequate groundwater and surface water flows to support downstream water-dependent ecosystems and maintain beneficial use of water.
However, where regional groundwater flow is present and pits are backfilled, throughflow conditions are likely to develop following groundwater rebound located within the saturated zone [116]. Throughflow may release solutes accumulated from previous oxidation, which may have an impact on the receiving groundwater quality as AMD. Consequently, it is equally important to understand the possible impacts that the backfill could have on post-closure groundwater quality. Quantification of the potential for solute release under these conditions may require solute leaching under anoxic conditions expected within inundated backfill [41,118].
Comparatively little is known of the functioning and especially concerning the water requirements of many of the key riparian species of the Pilbara and the ecosystems in which they occur [88,119]. Salinity in creek surface water and groundwater is low and, therefore, salinity–flooding interactions are rarely studied [120]. When undertaken, studies have generally only evaluated salinity associated with rising water tables, and not flooding associated with large, episodic, and short-lived flows. However, riparian plant diversity in arid regions is sensitive to changes in groundwater depth and salinity, as well as changes in soil moisture and salinity [121].
Stygofauna are likely to be present in all aquifers of the Pilbara [86], and water chemistry appears to have limited influence on stygofauna occurrence in the Pilbara. However, the distribution of taxa within an aquifer is primarily governed by alkalinity, salinity, and pH, with many taxa being restricted to single aquifers [122]. Few ecotoxicological data exist with which to assess the risks of trace metal mobility and uptake by subterranean fauna in the Pilbara. As a result, there are currently no groundwater ecosystem-specific water quality criteria available to identify metal toxicity risks to stygofauna. In the absence of these, Australian freshwater quality criteria [60] are conventionally applied [123]. However, these currently applied water quality targets in Australia may not be entirely protective of groundwater ecosystems.

Density-Driven Saline Seepage

Where pit lakes contain their waters and are terminal, they can increase solute concentrations through evapoconcentration and become increasingly saline over very long periods. This solute increase can lead to increased water density, which may cause density-driven flow into surrounding groundwater under certain hydrogeological conditions [124] (Figure 7).
As the pit lake water becomes denser over time due to evapoconcentration, the potential for migration into the aquifer beneath the pit floor is more probable [125]. If such leakage occurs, then the concentration rise within the void water is reduced as seepage causes mass loss of solutes from the system. Mineral precipitation may also occur when some solutes reach saturation indices. Although it is extremely difficult to predict the rates of leakage in a fractured hard rock environment [126,127], density-driven seepage represents a potential contaminant transport pathway though seepage of very saline waters into local groundwaters [36].

3.6. Pests and Diseases

Introduced predators, such as feral cats, foxes, and wild dogs, are common, and research has shifted from pastoral concerns (Thomson et al. 1992a, 1992b) to understanding the best practices to control invasive mammals for the purposes of biodiversity conservation [128]. Early settlers also introduced many grazing animals, now feral, including cattle (Bos primigenius), pigs (Sus scrofa), rabbits (Oryctolagus cuniculus), camels (Camelus dromedarius), donkeys (Equus asinus), and horses (Equus ferus caballus) [129].
North-western Australia lacks native crayfish, but the introduced red claw crayfish (Cherax quadricarinatus) is now known from three of the region’s five drainage basins, with limited management options in this remote area [130]. The species has been established through deliberate releases to provide fishing opportunities in areas where public access is permitted [131]. C. quadricarinatus has typically established itself in reservoirs before subsequently colonising natural systems, highlighting the potential for pit lakes to act as sources for further spread of freshwater crayfish [132].
There are also numerous existing and potential pathways for incursions from other vertebrate, invertebrate, and plant species from the aquarium trade into freshwater ecosystems in tropical Australia [133], such as the Pilbara.
Pilbara pit lakes also present potential for harbouring water-borne diseases [9,23]. Water-borne disease can be significant in northern parts of Australia, with the Ross River virus, Barmah Forest virus, and Australian encephalitis of particular concern [134]. The availability of quiescent surface water bodies at abandoned mines may provide a permanent breeding habitat for mosquitoes, some of which could be vectors for these human diseases [31,104]. Native animals tend to congregate around artificial or natural water bodies and are natural hosts of viruses causing disease, and these animals may facilitate transmission, e.g., to mine company personnel and recreational users. Some mosquito species breed in saline water, so the long-term salinisation expected in some pits would not decrease the disease risk from this source [135].
While fibrous minerals, e.g., crystalline silicas, such as crocidolite, can be found in many parts of WA [136], they are particularly prominent in the BIF of the Pilbara [137]. Within weathered or mineralised areas, crocidolite is replaced by goethite, which makes the mineral brittle and, thus, means that it does not pose a health risk. Hazardous fibrous minerals are not found within iron ore, as they have been replaced by iron oxide as part of the mineralisation process. Tuffs of fibrous materials can remain around pit perimeters at the closure of BWT voids, whether they form lakes or not, and materials characterisation should, therefore, include the identification of fibrous and asbestiform materials [138]. Although there is little guidance provided for the management of fibrous materials at closure, they typically require covering with non-fibrous materials.

3.7. Safety

Due to the nature of their formation from previous mining operations, pit lakes tend to have steep sides, and access can present a significant hazard in itself. Increasing the risk pit edges may be formed from unstable and erosive materials, and below-water gradients be steep and/or with sudden depth increases [139]. Pit lakes present a number of hazards for humans, including highwall failures and falls and risk of drowning [9]. Some pit lakes may also be accessible by the general public and, as such, may present a safety risk to people [140].
The rock of a pit highwall has been fractured by blasting and can be highly unstable [141]. Pit lake highwalls may, therefore, be unstable, particularly following rebounding groundwater pore pressures [142] and decades of wave action. Steep pit walls are not well-stabilised by water pressure until the lake water level equilibrates [143], a process that may take hundreds of years.
The Pilbara is in the top three regions of Western Australia for drowning cases, with lakes and dams being the second most likely places to drown, and remoteness being the key risk factor. Almost 1/4 of people who drowned were Aboriginal, although 2/3 were also people visiting the area [144]. Drowning was identified as the major cause of death in accidents that occurred in inactive or abandoned US mine sites [141]. Steep drop-offs, deep water, sharp rocks, flooded equipment, submerged wire, and industrial waste make swimming risky. With 13 pit lakes established [145], drownings in pit lakes have occurred in the Collie Pit lake District in Western Australia, with three in the last five years alone [146,147,148,149]. Traditional owners have repeatedly requested access to future pit lakes for recreational use, and there will be risks associated with these activities.
In 2018, a man died after two jet skis collided at the abandoned Atlas Iron Pardoo mine site in the Pilbara [150]. The mine site had been in care and maintenance for many years and was closed to the public, with physical restrictions on access and signs advising the public not to enter the site. However, vehicle access was still readily possible given the site’s location on the Great Northern Highway.

4. Opportunities

Pit lakes can present a range of potential opportunities at closure [9,151]. Pit lakes have been shown to present a multitude of opportunities for human recreation and regional economies, including for wildlife habitats, recreation, and primary production.
The fundamental alteration of the landscape and the creation of new landforms based on mining features, especially pit lakes, requires consideration of an alternative land use. A variety of industrial end uses have been proposed for pit lakes, especially pumped hydropower [152,153,154]. The combined storage potential from existing pit voids around Newman, Tom Price, and the Paraburdoo or Pannawonica townships in the Pilbara is estimated at about 200 GWh [155].
However, most post-closure opportunities are principally limited by pit lake water quality [156]. Although water quality may initially be good in Pilbara BWT voids, ongoing evapoconcentration and resultant salinisation is expected to lead to high TDS waters with fewer opportunities available long-term. The Pilbara’s remoteness to established communities and accessibility [157] will also play important roles in determining what, and if, opportunities can be realised in these pit lakes [158]. These two factors will be key to limiting PMLU in Pilbara pit lakes.
Pilot studies assessed the practicalities of options, such as agri-business, tourism, and cultural experiences, to build social value at a closed BHP mine site in the Pilbara [159]. Studies have also identified that there may be alternative economies for the beneficial use of Pilbara pit lake water for economic diversification and recreational waters and amenity [160]. However, the opportunity for mine voids, pit lakes, and infrastructure associated with mine closure to support irrigated agriculture has not yet been assessed [161]. This is largely due to the lack of data on potential water yields and water quality constraints available post-mining [157]. Most industrial or commercial uses of pit lakes will probably make more use of the regional industry needs for water resources to support current and near-future regional mining activities. Instead, projects in the Pilbara are largely proposed to involve low-intensity grazing and pastoral use [162] or to return to self-sustaining native vegetation where the underlying use is vacant or allocated Crown land. Nevertheless, there are a host of PMLUs that have been realised for pit lakes globally and already informally undertaken in existent Pilbara closed or abandoned sites that could apply to Pilbara BWT voids that form pit lakes [10,151,156,163,164,165,166,167,168]. These include swimming, water sports, such as kayaking and waterskiing, hunting and fishing, and wildlife habitats and watching, as well as aesthetic appeal and traditional/spiritual uses, primarily dependent upon water quality, especially salinity (Figure 8).

Aquatic Ecosystems

The reinstatement of natural systems (i.e., restoration) is possibly an unrealistic expectation for most larger metalliferous mines within the Pilbara [161]. However, provided that water quality risks are acceptable for receptors, a wildlife habitat remains the most likely opportunity [5] for remote Pilbara pit lakes. This will likely be as freshwater habitats for potentially centuries, then of reduced habitat value, as saline to hypersaline conditions develop thereafter for most terminal evaporative lakes.
Very little is known about the aquatic ecology in Australian pit lakes, and the few studies are typically focused upon macroinvertebrate communities [169,170,171]. Tropical Australian pit lake aquatic biota data is particularly unavailable [172], let alone for the Pilbara region. Nevertheless, studies of pit lake aquatic biota have collectively shown macroinvertebrate communities of limited diversity dominated by cosmopolitan and pollution tolerant taxa [171,173]. These findings suggest that, regardless of water quality, macroinvertebrate communities in pit lakes do not appear to be representative of natural waterbodies, possibly due to reduced habitat diversity of low quality even under good water quality [174].
Where there is no connectivity, there will be a significant limitation to most aquatic wildlife becoming established in Pilbara pit lakes due to an absence of regional permanent water bodies that could supply aquatic biota, e.g., propagules. Sources of nutrients include loadings in creek inflows of available fractions of sediment and dissolved and particulate organic matter. Nutrients may also be lost through uptake, adsorption, or settling. Interaction with primary producers includes nutrient consumption through photosynthesis (primarily phytoplankton in most pit lakes) and released through respiration.
Although terminal pit lakes will have limited catchment for biodiversity connectivity, flowthrough pit lakes will receive propagules from upstream during storm events. However, these freshwater aquatic biota are unlikely to be successful in increasingly saline pit lake environments. Nevertheless, even saline lakes can have high diversity and ecosystem value worldwide [175,176], and especially in the Pilbara region where saline-adapted flora and fauna are widespread [109].
The food web expected for a saline pit lake is very simple with low diversity and a short chain, in particular, through high rates of primary production being captured by saline-tolerant zooplankters, which form the basis of the hypersaline food web [177]. Regional lentic saline–water systems contain algae, brine shrimp, aquatic insects, and insect larvae, which form a food source for various bird species. However, macroinvertebrates, aside from zooplankters, are unlikely to be abundant, with almost all insects orders absent from these saline lakes [178].
PMLU opportunities may also present an increased risk through increased utilisation of pit lakes by humans, livestock, and wildlife [9,98,104]. For instance, trophic transfer of COPC through pit lake food chains has the potential to affect higher-order (e.g., bird, mammal) populations through impacts on developing embryos and eggs [105,179,180]. Western Australian pit lakes have also been recognised by some traditional owners (TOs) as an undesirable deviation from previous terrestrial land uses [181]. The absence of potable water due to salinisation has been recognised as a limitation of Pilbara pit lakes by TOs [182]. Also of concern is the protection of public drinking water source areas (PDWSAs) including regional water supply borefields.

5. Conclusions

Closure planning of Pilbara BWT voids should consider key potential hazards (Table 1). Many BWT open cut mining projects will result in pit lakes in the Pilbara, many of which will be very large, and many of which will also degrade in terms of water quality with increasing salinisation over time. These lakes can present direct risks to receptors, with the pit lake representing a transport mechanism for geochemical COPC. However, as an arid region, BWT mining risks in the region are also dominated by alterations to the hydrology and hydrogeology of largely unmodified natural waterways and freshwater aquifers. Therefore, Pilbara hazard assessment should particularly consider the availability of water present in pit lakes as a novel regional landform [5] and the risk of discharge to local waterways in addition to the more typical reduced water availability considered when mining in semi-arid/arid regions, e.g., South Africa, Nevada USA, Chile, etc. This latter point is important given the proximity of many current and proposed mining operations to significant regional waterways that have expansive floodplains (Figure 1). Thorough and transparent risk-assessment processes, again focusing on long-term water balance and water quality processes and outcomes, should underpin all closure planning strategies from initial mining approvals and permitting, through to final and definitive closure plan acceptance and rehabilitation works.
Although remote, social risks may also present a threat to local communities, especially in terms of impacts on safety and groundwater values. Furthermore, this remoteness also decreases the potential for realising practicable development of post-mining land uses for pit lakes.
Closure planning for pit lakes requires the consideration of a technically diverse list of topics. Consequently, a wide range of disciplines should be involved with closure planning of pit lake landforms. Nevertheless, what sets pit lake closure planning apart from planning of other mine closure landforms in the Pilbara is the need to also ensure interaction between these disciplines, especially with water as a unifying theme [183]. Key inputs to BWT void closure planning should also include the following:
  • Early and ongoing stakeholder engagement;
  • Multi-disciplinary inputs from subject matter experts especially related to water;
  • Sharing planning and benchmarking with other operations;
  • Both publication for peer-review and incorporating learnings from case studies,
  • Ad hoc research and trials;
  • Expert third-party advice.
Explicitly considered risk-based decisions should determine closure outcomes for BWT voids and when pit backfill to prevent pit lake formation will be warranted. PMLU goals should also focus on realistic and practicable outcomes, from stakeholders (including regulators) that are well informed regarding both pit lake closure science and practice during the planning process.
However, maintaining an open pit lake or backfilling a void should also be considered against the balance of potential risks and opportunities.

Funding

This research received no external funding.

Acknowledgments

I gratefully acknowledge the mining clients of the Pilbara that have contributed to this synthesis of BWT mining challenges in the region. I also acknowledge and thank reviewers for their constructive feedback.

Conflicts of Interest

Author Cherie D. McCullough was employed by the company Mine Lakes Consulting Pty Ltd. The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

References

  1. APEC. Mine Closure Checklist for Governments; Asia Pacific Economic Consortium (APEC): Ottawa, ON, Canada, 2018. [Google Scholar]
  2. ICMM. Integrated Mine Closure: Good Practice Guide; International Council on Mining and Metals (ICMM): London, UK, 2019; p. 132. [Google Scholar]
  3. Kragt, M.E.; Manero, A. Identifying Industry Practice, Barriers, and Opportunities for Mine Rehabilitation Completion Criteria in Western Australia. J. Environ. Manag. 2021, 287, 112258. [Google Scholar] [CrossRef]
  4. Manero, A.; Kragt, M.; Standish, R.; Miller, B.; Jasper, D.; Boggs, G.; Young, R. A Framework for Developing Completion Criteria for Mine Closure and Rehabilitation. J. Environ. Manag. 2020, 273, 111078. [Google Scholar] [CrossRef]
  5. McCullough, C.D.; Van Etten, E.J.B. Ecological Restoration of Novel Lake Districts: New Approaches for New Landscapes. Mine Water Environ. 2011, 30, 312–319. [Google Scholar] [CrossRef]
  6. McCullough, C.D. Pit Lakes and Mine Closure: Liability or Opportunity? AusIMM Bull. 2011, 20–21. [Google Scholar]
  7. Jones, H.; McCullough, C.D. Regulator Guidance and Legislation Relevant to Pit Lakes. In Mine Pit Lakes: Closure and Management; McCullough, C.D., Ed.; Australian Centre for Geomechanics: Perth, Australia, 2011; pp. 137–152. [Google Scholar]
  8. Williams, R.D. Regulatory Issues in the United States. In Mine Pit Lakes: Characteristics, Predictive Modeling, and Sustainability; Castendyk, D., Eary, T., Eds.; Society for Mining, Metallurgy, and Exploration (SME): Englewood, CO, USA, 2009; pp. 13–17. [Google Scholar]
  9. McCullough, C.D.; Lund, M.A. Opportunities for Sustainable Mining Pit Lakes in Australia. Mine Water Environ. 2006, 25, 220–226. [Google Scholar] [CrossRef]
  10. Apostu, I.M.; Lazar, M.; Faur, F. A Model to Evaluate the Flooding Opportunity and Sustainable Use of Former Open-Pits. Sustainability 2020, 12, 9275. [Google Scholar] [CrossRef]
  11. Caesarina, H.M.; Hirsan, F.P. Danau Seran, a Pit Lake in an Ex-Mining Area as an Opportunity for Sustainable Tourism. IOP Conf. Ser. Earth Environ. Sci. 2020, 413, 012026. [Google Scholar] [CrossRef]
  12. Latham, C.L.; Lazo-Skold, C. Problematic Pit: Closure Liability to Operational Opportunity. In Proceedings of the Mine Closure 2019: Proceedings of the 13th International Conference on Mine Closure, Perth, Australia, 3–5 September 2019. [Google Scholar]
  13. Côte, C.M.; Holloway, E.; Dunlop, J.; Chrystal, R.A. Leading Practice Approaches to Select Post-Mining Land Uses for Residual Mine Voids; Technical Paper; Office of the Queensland Mine Rehabilitation Commissioner, Queensland Government: Brisbane, Australia, 2023. [Google Scholar]
  14. McCullough, C.D.; Schultze, M.; Vandenberg, J.; Castendyk, D. Guidance for Mine Waste Disposal in Pit Lakes. In Proceedings of the Mine Closure, Perth, Australia, 26–28 November 2024. [Google Scholar]
  15. Castendyk, D.N. Conceptual Models of Pit Lakes. In Mine Pit Lakes: Characteristics, Predictive Modeling, and Sustainability; Castendyk, D., Eary, T., Eds.; Society for Mining, Metallurgy, and Exploration (SME): Englewood, CO, USA, 2009; pp. 61–76. [Google Scholar]
  16. Gammons, C.H.; Harris, L.N.; Castro, J.M.; Cott, P.A.; Hanna, B.W. Creating Lakes from Open Pit Mines: Processes and Considerations, with Emphasis on Northern Environments; Canadian Technical Report of Fisheries and Aquatic Sciences NWT Pit Lake Report 2836; Department of Fisheries and Oceans, Government of Canada: Ottawa, ON, Canada, 2009; p. 106. [Google Scholar]
  17. EPA. Cumulative Environmental Impacts of Development in the Pilbara Region: Advice of the Environmental Protection Authority to the Minister for Environment under Section 16(E) of the Environmental Protection Act 1986; EPA: Perth, Australia, 2014; p. 33. [Google Scholar]
  18. Peel, M.C.; Finlayson, B.L.; McMahon, T.A. Updated World Map of the Koppen-Geiger Climate Classification. Hydrol. Earth Syst. Sci. Discuss. 2007, 11, 1633–1644. [Google Scholar] [CrossRef]
  19. BOM. Bom Climate Averages for Newman Airport. Bureau of Meteorology, Commonwealth of Australia. Available online: https://www.bom.gov.au/climate/dwo/IDCJDW6096.latest.shtml (accessed on 9 August 2021).
  20. Kumar, R.N.; McCullough, C.D.; Lund, M.A. Upper and Lower Concentration Thresholds for Bioremediation of Acid Mine Drainage Using Bulk Organic Substrates. In Proceedings of the International Mine Water Association (IMWA) Congress, Bunbury, Australia, 4 October 2012. [Google Scholar]
  21. Pearce, S.; Barteaux, M. Instrumentation in Waste Rock Dumps: Going Deeper. In Proceedings of the 8th Australian Workshop on Acid and Metalliferous Drainage, Adelaide, Australia, 28 April–2 May 2014. [Google Scholar]
  22. Bussemaker, P.; Pang, K.L.; Barnes, P.; Latham, C.L.; McClenaghan, F. Closure Planning Challenges Associated with Mining Adjacent to Large Creek Lines. In Proceedings of the Mine Closure 2019: Proceedings of the 13th International Conference on Mine Closure, Perth, Australia, 3–5 September 2019. [Google Scholar]
  23. Pilbara Iron Ore Environmental Committee. Mining Below the Water Table in the Pilbara; Pilbara Iron Ore Environmental Committee (PIEC): Perth, Australia, 1999; p. 46. [Google Scholar]
  24. Ware, A.P.; Watkins, R.T. The Role of AMD in Pilbara Iron Ore: Mobilisation and Fate of Trace Elements During Surface and Groundwater Flow. In Proceedings of the 9th Australian Workshop on Acid Metalliferous Drainage, Burnie, Australia, 20–23 November 2017. [Google Scholar]
  25. Buller, E. Net Solute Load Response to the Installation of Infiltration Limiting Dry Cover Systems over Acid Forming Waste Piles. Master’s Thesis, University of Western Australia, Perth, Australia, 2014. [Google Scholar]
  26. Fajrin, A. Environmental Impact of Storage of Lignite and Black Shale Waste Rocks at South Jimblebar Iron Ore Mine, Western Australia. Master’s Thesis, Curtin University, Perth, Australia, 2013. [Google Scholar]
  27. Green, R.; Borden, R.K. Geochemical Risk Assessment Process for Rio Tinto’s Pilbara Iron Ore Mines. In Integrated Waste Management; Kumar, S., Ed.; InTech: London, UK, 2011; pp. 365–390. [Google Scholar]
  28. Pepper, M.; Doughty, P.; Arculus, R.; Keogh, J.S. Landforms Predict Phylogenetic Structure on One of the World’s Most Ancient Surfaces. BMC Evol. Biol. 2008, 8, 152. [Google Scholar] [CrossRef]
  29. Pepper, M.; Doughty, P.; Keogh, J.S. Geodiversity and Endemism in the Iconic Australian Pilbara Region: A Review of Landscape Evolution and Biotic Response in an Ancient Refugium. J. Biogeogr. 2013, 40, 1225–1239. [Google Scholar] [CrossRef]
  30. Doughty, P.; Rolfe, J.K.; Burbidge, A.H.; Pearson, D.J.; Kendrick, P.G. Herpetological Assemblages of the Pilbara Biogeographic Region, Western Australia: Ecological Associations, Biogeographic Patterns and Conservation. Rec. West. Aust. Mus. Suppl. 2011, 78, 315–341. [Google Scholar] [CrossRef]
  31. Johnson, S.L.; Wright, A.H. Mine Void Water Resource Issues in Western Australia; Water and Rivers Commission: Perth, Australia, 2003; p. 93. [Google Scholar]
  32. BHP. Mt Whaleback Mine (Newman West). Available online: https://www.bhp.com/what-we-do/global-locations/australia/western-australia/mt-whaleback (accessed on 9 October 2024).
  33. Johnson, S.L.; Wright, A.H. Central Pilbara Groundwater Study; Water and Rivers Commission: Perth, Australia, 2001; p. 93. [Google Scholar]
  34. Mallet, C.W.; Mark, M.R. Review of the Management and Impact of Mining Voids. In Proceedings of the 20th Annual Environmental Workshop, Perth, Australia, 2–6 October 1995. [Google Scholar]
  35. Niccoli, W.L. Hydrologic Characteristics and Classifications of Pit Lakes. In Mine Pit Lakes: Characteristics, Predictive Modeling, and Sustainability; Castendyk, D., Eary, T., Eds.; Society for Mining, Metallurgy, and Exploration (SME): Englewood, CO, USA, 2009; pp. 33–43. [Google Scholar]
  36. McCullough, C.D.; Marchand, G.; Unseld, J. Mine Closure of Pit Lakes as Terminal Sinks: Best Available Practice When Options Are Limited? Mine Water Environ. 2013, 32, 302–313. [Google Scholar] [CrossRef]
  37. McCullough, C.D.; Schultze, M. Engineered River Flow-through to Improve Mine Pit Lake and River Water Values. Sci. Total Environ. 2018, 640, 217–231. [Google Scholar] [CrossRef]
  38. McCullough, C.D. Consequences and Opportunities of River Breach and Decant from an Acidic Mine Pit Lake. Ecol. Eng. 2015, 85, 328–338. [Google Scholar] [CrossRef]
  39. Rojas, R.; Commander, P.; McFarlane, D.; Ali, R.; Dawes, W.; Barron, O.; Hodgson, G.; Charles, S. Groundwater Resource Assessment and Conceptualization in the Pilbara Region, Western Australia. Earth Syst. Environ. 2018, 2, 345–365. [Google Scholar] [CrossRef]
  40. Appleyard, S. Preliminary Assessment: Discharge of Nitrogen by Groundwater to the Marine Environment in the Pilbara Region; Water and Rivers Commission: Perth, Australia, 2000; p. 12. [Google Scholar]
  41. Watson, A.; Linklater, C.; Chapman, J.; Marton, R. Weathered Sulfidic Waste—Laboratory-Scale Tests for Assessing Water Quality in Backfilled Pits. In Proceedings of the 9th Australian Workshop on Acid Metalliferous Drainage, Burnie, Tasmania, 20–23 November 2017. [Google Scholar]
  42. Miller, G.C.; Lyons, W.B.; Davis, A. Understanding the Water Quality of Pit Lakes. Environ. Sci. Technol. 1996, 30, 118A–123A. [Google Scholar] [CrossRef]
  43. Vandenberg, J.; Lauzon, N.; Prakash, S.; Salzsauler, K. Use of Water Quality Models for Design and Evaluation of Pit Lakes. In Mine Pit Lakes: Closure and Management; McCullough, C.D., Ed.; Australian Centre for Geomechanics: Perth, Australia, 2011; pp. 63–80. [Google Scholar]
  44. Hannam, S.; Green, R. Rtio Ampl Risk Assessment Tool. In Proceedings of the 8th Australian Workshop on Acid and Metalliferous Drainage, Adelaide, Australia, 28 April–2 May 2014. [Google Scholar]
  45. Garvie, A.; Linklater, C.; Staines, R.; Chapman, J.; Green, R. Oxidation and Solute Accumulation in Pit Wall Rock: Limiting Changes to Pit Lake Water Quality. In Proceedings of the 8th Australian Workshop on Acid Metalliferous Drainage, Adelaide, Australia, 29 April–2 May 2014. [Google Scholar]
  46. Manewell, N. The Hydrogeology and Hydrochemistry of the Mt. Tom Price Mine, Pilbara, Western Australia—A Groundwater Flow Model; University of Canterbury: Christchurch, New Zealand, 2008. [Google Scholar]
  47. Hendry, M.J.; Wassenaar, L.I.; Barbour, S.L.; Schabert, M.S.; Birkham, T.K.; Fedec, T.; Schmeling, E.E. Assessing the Fate of Explosives Derived Nitrate in Mine Waste Rock Dumps Using the Stable Isotopes of Oxygen and Nitrogen. Sci. Total Environ. 2018, 640, 127–137. [Google Scholar] [CrossRef]
  48. Mahmood, F.N.; Barbour, S.L.; Kennedy, C.; Hendry, M.J. Nitrate Release from Waste Rock Dumps in the Elk Valley, British Columbia, Canada. Sci. Total Environ. 2017, 605, 915–928. [Google Scholar] [CrossRef]
  49. Camargo, J.A.; Alonso, A.; Salamanca, A. Nitrate Toxicity to Aquatic Animals: A Review with New Data for Freshwater Invertebrates. Chemosphere 2005, 58, 1255–1267. [Google Scholar] [CrossRef]
  50. Bosman, C. The Hidden Dragon: Nitrate Pollution from Open-Pit Mines. A Case Study from the Limpopo Province, South Africa. In Proceedings of the International Mine Water Conference, Pretoria, South Africa, 19–23 October 2009. [Google Scholar]
  51. van Dam, R.A.; Bankin, K.; Parry, D. Derivation of Site-Specific Guideline Values for Nitrate Toxicity in Pilbara Receiving Waters with High Hardness. Integr. Environ. Assess. Manag. 2022, 18, 1035–1046. [Google Scholar] [CrossRef]
  52. McCullough, C.D. The Importance of Nitrate Dynamics in Mine Pit Lakes of Drier Regions. Mine Water Environ. 2024, 43, 231–254. [Google Scholar] [CrossRef]
  53. Boehrer, B.; Schultze, M. On the Relevance of Meromixis in Mine Pit Lakes. In Proceedings of the 7th International Conference on Acid Rock Drainage (ICARD), St Louis, MI, USA, 27–30 March 2006. [Google Scholar]
  54. Jpehnk, K.; Uhlmann, W. Persistence of Meromictic Stratification in Post Mining Lakes. In Proceedings of the IMWA Conference 2016, Freiberg, Germany, 11–15 July 2016. [Google Scholar]
  55. Schultze, M.; Castendyk, D.; Wendt-Potthoff, K.; Sanchez-Espana, J.; Boehrer, B. On the Relevance of Meromixis in Pit Lakes—An Update. In Proceedings of the IMWA Conference 2016, Freiberg, Germany, 11–15 July 2016. [Google Scholar]
  56. Gerrard, J.P. Stormwater Harvesting in Open Pit Voids as a Means of Supplementing and Maintaining Quality of Local Water Resources in the Northern Goldfields of Western Australia. In Proceedings of the Goldfields Environmental Management Group Workshop on Environmental Management 2006, Kalgoorlie, Australia, 24–26 May 2002. [Google Scholar]
  57. Kumar, N.R.; McCullough, C.D.; Lund, M.A. Pit Lakes in Australia. In Acidic Pit Lakes—The Legacy of Coal and Metal Surface Mines; Geller, W., Schultze, M., Kleinmann, R., Wolkersdorfer, C., Eds.; Springer: Berlin/Heidelberg, Germany, 2013; pp. 342–361. [Google Scholar]
  58. Boland, K.T.; Padovan, A.V. Seasonal Stratification and Mixing in a Recently Flooded Mining Void in Tropical Australia. Lakes Reserv. Res. Manag. 2002, 7, 125–131. [Google Scholar] [CrossRef]
  59. Linklater, C.; Chapman, J.; Brown, P.; Green, R.; Leake, S. Assessing Metal Leachability from Low Sulfur Wastes—Sequential Extraction Methods. In Proceedings of the 9th Australian Workshop on Acid Metalliferous Dranaige, Burnie, Tasmania, 20–23 November 2017. [Google Scholar]
  60. ANZG. Australian and New Zealand Guidelines for Fresh and Marine Water Quality; Australian and New Zealand Governments (ANZG) and Australian State and Territory Governments: Canberra, Australia, 2018. [Google Scholar]
  61. McCullough, C.D.; Pearce, J.I. What Do Elevated Background Contaminant Concentrations Mean for AMD Risk Assessment and Management in Western Australia? In Proceedings of the 8th Australian Workshop on Acid and Metalliferous Drainage, Adelaide, Australia, 28 April–2 May 2014. [Google Scholar]
  62. van Dam, R.A.; Harford, A.J.; Lunn, S.A.; Gagnon, M.M. Identifying the Cause of Toxicity of a Saline Mine Water. PLoS ONE 2014, 9, e106857. [Google Scholar] [CrossRef]
  63. Luo, J.; Wang, F.; Tomsu, C.; Druzynski, A.; Monninkhoff, B. Mine Water Management Close to Groundwater Systems of Varying Salinity, Pilbara, Western Australia. In Proceedings of the an Interdisciplinary Response to Mine Water Challenges-the Proceedings of the 12th IMWA Congress, Xuzhou, China, 18–22 August 2014. [Google Scholar]
  64. Green, R.; Linklater, C.; Lee, S.; Terrusi, L.; Glasson, K. Rio Tinto’s Framework for Evaluating Risks from Low Sulfur Waste Rock. In Proceedings of the Mine Closure 2019: Proceedings of the 13th International Conference on Mine Closure, Perth, Australia, 3–5 September 2019. [Google Scholar]
  65. Linklater, C.; Watson, A.; Chapman, J.; Green, R.; Lee, S. Weathering and Oxidation Rates in Black Shales. In Proceedings of the 10th International Conference on Acid Rock Drainage & IMWA Annual Conference, Vancouver, BC, Canada, 21–24 April 2015. [Google Scholar]
  66. Pearce, J.; Pearce, S.; Marton, R. Why Variable Oxidation Rates Are Needed for the Prediction of AMD from Dynamic Waste Rock Dumps. In Proceedings of the 9th Australian Workshop on Acid and Metalliferous Drainage, Burnie, Australia, 20–23 November 2017. [Google Scholar]
  67. Lim, E.; Beckett, K.; Jaen, W.; Kumar, A. Probabilistic Analysis of Mine Void Salinity and Lake Level Associated with Climate Change. In Proceedings of the International Mine Water Association (IMWA) Congress, Sydney, NS, Canada, 5–9 September 2010. [Google Scholar]
  68. McJannet, D.; Hawdon, A.; Van Niel, T.; Boadle, D.; Baker, B.; Trefry, M.; Rea, I. Measurements of Evaporation from a Mine Void Lake and Testing of Modelling Approaches. J. Hydrol. 2017, 555, 631–647. [Google Scholar] [CrossRef]
  69. Hall, J.W.; Middlemis, H.; Waters, P.J.; Rozlapa, K.L. Integration of Groundwater Modelling with Mine Planning to Optimise Mine Closure Plans—The Marillana Creek (Yandi) Mine Story. In Proceedings of the Mine Closure 2006: Proceedings of the First International Seminar on Mine Closure, Perth, Australia, 13–15 September 2006. [Google Scholar]
  70. Maest, A.; Prucha, R.; Wobus, C. Hydrologic and Water Quality Modeling of the Pebble Mine Project Pit Lake and Downstream Environment after Mine Closure. Minerals 2020, 10, 727. [Google Scholar] [CrossRef]
  71. Gardiner, S.J. Impacts of Mining and Mine Closure on Water Quality and the Nature of the Shallow Aquifier, Yandi Iron Ore Mine. Ph.D. Thesis, Curtin University, Perth, Australia, 2003. [Google Scholar]
  72. Dunbar, D.S. Modelling of Pit Lakes. In Acidic Pit Lakes—Legacies of Surface Mining on Coal and Metal Ores; Geller, W., Schultze, M., Kleinmann, R.L.P., Wolkersdorfer, C., Eds.; Springer: Berlin/Heidelberg, Germany, 2013; pp. 186–224. [Google Scholar]
  73. DOW. Western Australia Water in Mining Guideline; Department of Water, Government of Western Australia: Perth, Australia, 2013; p. 75. [Google Scholar]
  74. Germs, W.; Race, G.; Green, R.; Marton, R. Developing Pilbara Pit Lake Analogues to Inform Closure Considerations. In Proceedings of the 9th Australian Workshop on Acid Metalliferous Drainage, Burnie, Tasmania, 20–23 November 2017. [Google Scholar]
  75. Eary, L.E. Predicting the Effects of Evapoconcentration of Water Quality in Pit Lakes. Geochem. Explor. 1998, 64, 223–236. [Google Scholar] [CrossRef]
  76. Eary, L.E. Geochemical and Equilibrium Trends in Mine Pit Lakes. Appl. Geochem. 1999, 14, 963–987. [Google Scholar] [CrossRef]
  77. Kozak, W.; Atkinon, S.; Pearson, B. Creek Reinstatement over Backfilled Mine Pits. In Proceedings of the Life of Mine, Brisbane, Australia, 28–30 April 2021. [Google Scholar]
  78. Atkinson, S.; Markham, A.; Rafty, M.; Heyting, M. Pilbara Creek Diversions: Resilience Gained through Increased Ore Recovery and an Integrated Approach to Design. In Proceedings of the AUSIMM Iron Ore Conference, Perth, Australia, 24–26 July 2017. [Google Scholar]
  79. Flatley, A.; Markham, A. Establishing Effective Mine Closure Criteria for River Diversion Channels. J. Environ. Manag. 2021, 287, 112287. [Google Scholar] [CrossRef]
  80. Puhalovich, A.A.; Coghill, M. Management of Mine Wastes Using Pit/Underground Void Backfilling Methods: Current Issues and Approaches. In Mine Pit Lakes: Closure and Management; McCullough, C.D., Ed.; Australian Centre for Geomechanics: Perth, Australia, 2011; pp. 3–14. [Google Scholar]
  81. Harvey, M.; Price, K.; Pearcey, M. Rethinking Hydrologic Design Criteria for Mine Closure. In Proceedings of the International Mine Water Association (IMWA) Congress, Christchurch, New Zealand, 9–13 November 2020. [Google Scholar]
  82. White, K.; Hardie, R.; Lucas, R.; Merritt, J.; Kirsch, B. The Evolution of Watercourse Diversion Design in Central Queensland Coal Mines. In Proceedings of the 7th Australian Stream Management Conference, Townsville, Australia, 8 August 2014. [Google Scholar]
  83. Bozan, C.; Wallis, I.; Cook, P.G.; Dogramaci, S. Groundwater-Level Recovery Following Closure of Open-Pit Mines. Hydrogeol. J. 2022, 30, 1819–1832. [Google Scholar] [CrossRef]
  84. Neumann, C.; Beer, J.; Blodau, C.; Peiffer, S.; Fleckenstein, J.H. Fleckenstein. Spatial Patterns of Groundwater-Lake Exchange—Implications for Acid Neutralization Processes in an Acid Mine Lake. Hydrol. Process. 2013, 27, 3240–3253. [Google Scholar] [CrossRef]
  85. Zhao, L.; Ren, T.; Wang, N. Groundwater Impact of Open Cut Coal Mine and an Assessment Methodology: A Case Study in NSW. Int. J. Min. Sci. Technol. 2017, 27, 861–866. [Google Scholar] [CrossRef]
  86. Halse, S.; Scanlon, M.D.; Cocking, J.S.; Barron, H.J.; Richardson, J.B.; Eberhard, S. Pilbara Stygofauna: Deep Groundwater of an Arid Landscape Contains Globally Significant Radiation of Biodiversity. Rec. West. Aust. Mus. Suppl. 2014, 78, 443. [Google Scholar] [CrossRef]
  87. Eamus, D.; Froend, R.; Loomes, R.; Hose, G.; Murray, B. A Functional Methodology for Determining the Groundwater Regime Needed to Maintain the Health of Groundwater-Dependent Vegetation. Aust. J. Bot. 2006, 54, 97–114. [Google Scholar] [CrossRef]
  88. McLean, E. Patterns of Water Use by the Riparian Tree Melaleuca argentea in Semi-Arid Northwest Australia. Ph.D. Thesis, University of Western Australia, Perth, Australia, 2014. [Google Scholar]
  89. Loomes, R. Determining Water Level Ranges of Pilbara Riparian Species. In Environmental Water Report Series, 1833-6582; Department of Water (DoW): Perth, Australia, 2010; No. 17. [Google Scholar]
  90. Franklin, D.; Brocklehurst, P.; Lynch, D.; Bowman, D. Niche Differentiation and Regeneration in the Seasonally Flooded Melaleuca Forests of Northern Australia. J. Trop. Ecol. 2007, 23, 457–467. [Google Scholar] [CrossRef]
  91. Howe, P.; Pritchard, J.; Carter, J.; New, C. Addressing the Potential Effects of Mine Dewatering on Terrestrial Groundwater Dependent Ecosystems—Pilbara Region, Western Australia; Gecamin Ltd.: Santiago, Chile, 2009. [Google Scholar]
  92. Muir, B. Field Monitoring of Vegetation Health. In Management of Groundwater Dependent Vegetation in the Central Pilbara Iron Ore Mining Province; Ecosystems Research Group, University of Western Australia: Perth, Australia, 1995. [Google Scholar]
  93. Humphreys, W.F. Aquifers: The Ultimate Groundwater-Dependent Ecosystems. Aust. J. Bot. 2006, 54, 115–132. [Google Scholar] [CrossRef]
  94. Mokany, K.; Harwood, T.D.; Ferrier, S. Improving Links between Environmental Accounting and Scenario-Based Cumulative Impact Assessment for Better-Informed Biodiversity Decisions. J. Appl. Ecol. 2019, 56, 2732–2741. [Google Scholar] [CrossRef]
  95. Eisler, R.; Wiemeyer, S.N. Cyanide Hazards to Plants and Animals from Gold Mining and Related Water Issues. In Reviews of Environmental Contamination and Toxicology; Ware, G.W., Nigg, H.N., Doerge, D.R., Eds.; Springer: New York, NY, USA, 2004; pp. 21–54. [Google Scholar]
  96. Das, S.; Mukherjee, A.; Gupta, S. Spatial Prioritization of Selected Mining Pit Lakes from Eastern Coalfields Region, India: A Species Distribution Modelling Approach. Conserv. Sci. Pract. 2020, 2, e216. [Google Scholar] [CrossRef]
  97. Griffiths, S.R.; Donato, D.B.; Coulson, G.; Lumsden, L.F. High Levels of Activity of Bats at Gold Mining Water Bodies: Implications for Compliance with the International Cyanide Management Code. Environ. Sci. Pollut. Res. 2014, 21, 7263–7275. [Google Scholar] [CrossRef]
  98. Hinwood, A.; Heyworth, J.; Tanner, H.; Mccullough, C. Recreational Use of Acidic Pit Lakes—Human Health Considerations for Post Closure Planning. J. Water Resour. Prot. 2012, 4, 1061–1070. [Google Scholar] [CrossRef]
  99. Leslie, R. Nature of Biology; Wiley: Sydney, Australia, 2016. [Google Scholar]
  100. Dawson, T.J.; Denny, M.J.S.; Russell, E.M.; Ellis, B. Water Usage and Diet Preferences of Free Ranging Kangaroos, Sheep and Feral Goats in the Australian Arid Zone During Summer. J. Zool. 1975, 177, 1–23. [Google Scholar] [CrossRef]
  101. Allen, B.L. Do Desert Dingoes Drink Daily? Visitation Rates at Remote Waterpoints in the Strzelecki Desert. Aust. Mammal. 2012, 34, 251–256. [Google Scholar] [CrossRef]
  102. Griffiths, S.R.; Donato, D.B.; Lumsden, L.F.; Coulson, G. Hypersalinity Reduces the Risk of Cyanide Toxicosis to Insectivorous Bats Interacting with Wastewater Impoundments at Gold Mines. Ecotoxicol. Environ. Saf. 2014, 99, 28–34. [Google Scholar] [CrossRef]
  103. Griffiths, S.R.; Smith, G.B.; Donato, D.B.; Gillespie, C.G. Factors Influencing the Risk of Wildlife Cyanide Poisoning on a Tailings Storage Facility in the Eastern Goldfields of Western Australia. Ecotoxicol. Environ. Saf. 2009, 72, 1579–1586. [Google Scholar] [CrossRef]
  104. Doupé, R.G.; Lymbery, A.J. Environmental Risks Associated with Beneficial End Uses of Mine Lakes in Southwestern Australia. Mine Water Environ. 2005, 24, 134–138. [Google Scholar] [CrossRef]
  105. McCullough, C.D.; Sturgess, S. Human Health and Environmental Risk Assessment for Closure Planning of the Argyle Diamond Mine Pit Lake. In Proceedings of the International Mine Water Association (IMWA) Congress 2020, Christchurch, New Zealand, 9–13 November 2020. [Google Scholar]
  106. Lund, M.A.; Blanchette, M.L. Closing Pit Lakes as Aquatic Ecosystems: Risk, Reality, and Future Uses. WIREs Water 2023, 10, e1648. [Google Scholar] [CrossRef]
  107. Harvey, M.D.; Pearcey, M.R.; Price, K.; Devkota, B.; Mateo, B. Geomorphic, Hydraulic and Sediment Transport Modelling for Mine-Related Channel Realignment-Case Study: Caves Creek, Pilbara, Western Australia. In Proceedings of the Hydrology and Water Resources Symposium 2014, Perth, Australia, 24–27 February 2014. [Google Scholar]
  108. DOW. Ecological Water Requirements of the Lower De Grey River; Department of Water (DOW): Perth, Australia, 2012. [Google Scholar]
  109. Pinder, A.M.; Halse, S.A.; Shiel, R.J.; McRae, J.M. An Arid Zone Awash with Diversity: Patterns in the Distribution of Aquatic Invertebrates in the Pilbara Region of Western Australia. Rec. West. Aust. Mus. Suppl. 2010, 78, 205–246. [Google Scholar] [CrossRef]
  110. Florentine, S.K. Ecology of Eucalyptus victrix in Grassland in the Floodplain of the Fortescue Rive. Ph.D. Thesis, Curtin University, School of Environmental Biology, Perth, Australia, 1999. [Google Scholar]
  111. McCullough, C.D.; Ballot, E.; Short, D. Breach and Decant of an Acid Mine Lake by a Eutrophic River: River Water Quality and Limitations of Use. In Proceedings of the Mine Water Solutions 2013 Congress, Lima, Peru, 6–9 August 2013. [Google Scholar]
  112. Jha, A. What Is a Representative Pan Factor Value for the Eastern Pilbara? In Proceedings of the International Mine Water Association (IMWA) Congress, Bunbury, Australia, 4 October 2012. [Google Scholar]
  113. Moise, A.; Abbs, D.; Bhend, J.; Chiew, F.; Church, J.; Ekström, M.; Kirono, D.; Lenton, A. Climate Change in Australia Projections for Australia’s Natural Resource Management Regions: Cluster Reports; CSIRO and Bureau of Meteorology: Melbourne, Australia, 2015. [Google Scholar]
  114. Cullen, L.E.; Grierson, P.F. A Stable Oxygen, but Not Carbon, Isotope Chronology of Callitris Columellaris Reflects Recent Climate Change in North-Western Australia. Clim. Change 2007, 85, 213–229. [Google Scholar] [CrossRef]
  115. Paulsson, O.; Widerlund, A. Modelled Impact of Climate Change Scenarios on Hydrodynamics and Water Quality of the Rävlidmyran Pit Lake, Northern Sweden. Appl. Geochem. 2022, 139, 105235. [Google Scholar] [CrossRef]
  116. McCullough, C.D.; O’Grady, B. Closure of an Australian Pit Lake with AMD Using a Terminal Water Balance as an Evaporative Sink. In Proceedings of the International Mine Water Association (IMWA) Conference 2022, Christchurch, New Zealand, 6–10 November 2022. [Google Scholar]
  117. Vandenberg, J.; Schultze, M.; McCullough, C.D.; Castendyk, D. The Future Direction of Pit Lakes: Part 2, Corporate and Regulatory Needs to Improve Management. Mine Water Environ. 2022, 41, 544–556. [Google Scholar] [CrossRef]
  118. Watson, A.; Linklater, C.; Chapman, J. Backfilled Pits—Laboratory-Scale Tests for Assessing Impacts on Groundwater. In Proceedings of the Life of Mine, Brisbane, Australia, 28–30 September 2016. [Google Scholar]
  119. O’Grady, A.P.; Eamus, D.; Cook, P.G.; Lamontagne, S. Lamontagne. Comparative Water Use by Riparian Trees Melaleuca argentea and Corymbia Bella in the Wet-Dry Tropics of Northern Australia. Tree Physiol. 2006, 26, 219–228. [Google Scholar] [CrossRef]
  120. Argus, R. Flooding Responses of Riparian Eucalypts in the Pilbara Region of Western Australia. Ph.D. Thesis, University of Western Australia, Perth, Australia, 2018. [Google Scholar]
  121. Zeng, Y.; Zhao, C.; Shi, F.; Schneider, M.; Lv, G.; Li, Y. Impact of Groundwater Depth and Soil Salinity on Riparian Plant Diversity and Distribution in an Arid Area of China. Sci. Rep. 2020, 10, 7272. [Google Scholar] [CrossRef]
  122. Reeves, J.; De, P.; Ae, D.; Halse, S. Groundwater Ostracods from the Arid Pilbara Region of Northwestern Australia: Distribution and Water Chemistry. Hydrobiologia 2007, 585, 99–118. [Google Scholar] [CrossRef]
  123. Hose, G.C.; Symington, K.; Lott, M.J.; Lategan, M.J. The Toxicity of Arsenic(iii), Chromium(Vi) and Zinc to Groundwater Copepods. Environ. Sci. Pollut. Res. Int. 2016, 23, 18704–18713. [Google Scholar] [CrossRef]
  124. Gvirtzman, H. Groundwater Hydrology and Paleohydrology at the Dead Sea Rift Valley. In New Frontiers in Dead Sea Paleoenvironmental Research; Enzel, Y., Agnon, A., Stein, M., Eds.; GSA Book: Washington, DC, USA, 2006; pp. 95–111. [Google Scholar]
  125. Roemer, G.; Burgess, C.; Cadle, S. Variable-Density Transport Modeling in Hypersaline Pit Lakes. In Proceedings of the Joint International Conference on Acid Rock Drainage ICARD/International Mine Water Association (IMWA) Congress, Santiago, Chile, 21–24 April 2015. [Google Scholar]
  126. Barr, A.D.; Turner, J.V. Modelling Long-Term Chemical Composition of Waterbodies in Abandoned Mining Voids. In Proceedings of the 3rd International Hydrology and Water Resources Symposium, Perth, Australia, 20–23 November 2000. [Google Scholar]
  127. Schultze, M.; Vandenberg, J.; McCullough, C.D.; Castendyk, D. The Future Direction of Pit Lakes: Part 1, Research Needs. Mine Water Environ. 2022, 41, 533–543. [Google Scholar] [CrossRef]
  128. Moro, D.; Morris, K.; van Leeuwen, S.; Davie, H. A Framework of Integrated Research for Managing Introduced Predators in the Pilbara Bioregion, Western Australia. Aust. Mammal. 2021, 43, 265–276. [Google Scholar] [CrossRef]
  129. Carwardine, J.; Nicol, S.; Van Leeuwen, S.; Walters, B.; Firn, J.; Reeson, A.; Martin, T.; Chades, I. Priority Threat Management for Pilbara Species of Conservation Significance. 2014. Available online: https://eprints.qut.edu.au/73054/ (accessed on 9 October 2024).
  130. Pinder, A.; Harman, A.; Bird, C.; Quinlan, K.; Angel, F.; Cowan, M.; Lewis, L.; Thillainath, E. Spread of the Non-Native Redclaw Crayfish Cherax quadricarinatus (Von Martens, 1868) into Natural Waters of the Pilbara Region of Western Australia, with Observations on Potential Adverse Ecological Effects. BioInvasions Rec. 2019, 8, 882–897. [Google Scholar] [CrossRef]
  131. Doupé, R.; Morgan, D.; Gill, H.; Rowland, A. Introduction of Redclaw Crayfish Cherax quadricarinatus (Von Martens) to Lake Kununurra, Ord River, Western Australia: Prospects for a ‘Yabby’ in the Kimberley. J. R. Soc. West. Aust. 2004, 87, 187. [Google Scholar]
  132. Beatty, S.J.; Ramsay, A.; Pinder, A.M.; Morgan, D.L. Reservoirs Act as Footholds for an Invasive Freshwater Crayfish. Pac. Conserv. Biol. 2020, 26, 78–83. [Google Scholar] [CrossRef]
  133. Ebner, B.; Millington, M.; Holmes, B.; Wilson, D.; Sydes, T.; Bickel, T.O.; Hammer, M.; Lach, L.; Schaffer, J.; Lymbery, A. Scoping the Biosecurity Risks and Appropriate Management Relating to the Freshwater Ornamental Aquarium Trade Across Northern Australia; Centre for Tropical Water and Aquatic Ecosystem Research (TropWATER): Cairns, Australia, 2020; p. 96. [Google Scholar]
  134. Mackenzie, J.S.; Lindsay, M.D.A.; Smith, D.W.; Imrie, A. The Ecology and Epidemiology of Ross River and Murray Valley Encephalitis Viruses in Western Australia: Examples of One Health in Action. Trans. R. Soc. Trop. Med. Hyg. 2017, 111, 248–254. [Google Scholar] [CrossRef]
  135. Norris, D.E. Mosquito-Borne Diseases as a Consequence of Land Use Change. EcoHealth 2004, 1, 19–24. [Google Scholar] [CrossRef]
  136. Banerjee, K.K.; Wang, H.; Pisaniello, D. Iron-Ore Dust and Its Health Impacts. Environ. Health 2006, 6, 11–16. [Google Scholar]
  137. Rogers, A.J. Exposures Estimates of the Wittenoom Mining Workforce and Town Residents—Implications Associated with Risk Estimation for Persons Exposed to Asbestiform Riebeckite. Toxicol. Appl. Pharmacol. 2018, 361, 168–170. [Google Scholar] [CrossRef]
  138. DMIRS. Mine Closure Plan Guidance—How to Prepare a Mine Closure Plan in Accordance with Part 1 of the Statutory Guidelines for Mine Closure Plans; Western Australian Department of Mines, Industry Regulation and Safety (DMIRS): Perth, Australia, 2020; p. 74. [Google Scholar]
  139. Ross, T.; McCullough, C.D. Health and Safety Working around Pit Lakes. In Mine Pit Lakes: Closure and Management; McCullough, C.D., Ed.; Australian Centre for Geomechanics: Perth, Australia, 2011; pp. 167–181. [Google Scholar]
  140. McCullough, C.D.; Diaz, A. Integrated Closure Planning for a High Altitude Pit Lake in the Peruvian Andes. In Proceedings of the International Mine Water Association (IMWA) Congress 2020, Christchurch, New Zealand, 9–13 November 2020. [Google Scholar]
  141. King, H. Abandoned Mine and Quarry Accidents Claim Several Lives Per Year. 2017. Available online: https://geology.com/articles/abandoned-mines.shtml (accessed on 9 October 2024).
  142. Kavvadas, M.; Roumpos, C.; Servou, A.; Paraskevis, N. Geotechnical Issues in Decommissioning Surface Lignite Mines; the Case of Amyntaion Mine in Greece. Mining 2022, 2, 278–296. [Google Scholar] [CrossRef]
  143. Schultze, M.; Pokrandt, K.-H.; Hille, W. Pit Lakes of the Central German Lignite Mining District: Creation, Morphometry and Water Quality Aspects. Limnologica 2010, 40, 148–155. [Google Scholar] [CrossRef]
  144. RLS/HOH. WA Drowning Report 2022; Royal Life Saving (RLS), Government of Western Australia, Department of Public Health (DOH): Perth, Australia, 2023; p. 30. [Google Scholar]
  145. Lund, M.A.; McCullough, C.D.; Kumar, N.R. The Collie Pit Lake District, Western Australia: An Overview. In Proceedings of the International Mine Water Association (IMWA) Congress, Bunbury, Australia, 4 October 2012. [Google Scholar]
  146. Van Der Wielen, S.; Hampton, S. Police Divers Recover Body from Stockton Lake. The West Australian, 11 September 2023. [Google Scholar]
  147. Hatch, D. Frantic Effort to Save Drowning Man. The West Australian, 28 December 2007; p. 14. [Google Scholar]
  148. Van Der Wielen, S. Black Diamond Lake: Police Find Body of Missing Swimmer at Popular Collie Lake. Perth Now, 26 December 2022. [Google Scholar]
  149. Tirant, B. Man Drowns at Collie’s Stockton Lake. Bunbury Mail, 9 January 2019. [Google Scholar]
  150. Dougherty, R. Man Killed in Jet Ski Collision at Abandoned Atlas Iron Mine Site in the Pilbara. Perth Now, 14 March 2018. [Google Scholar]
  151. McCullough, C.D.; Hunt, D.; Evans, L.H. Sustainable Development of Open Pit Mines: Creating Beneficial End Uses for Pit Lakes. In Mine Pit Lakes: Characteristics, Predictive Modeling, and Sustainability; Castendyk, D., Eary, T., Eds.; Society for Mining, Metallurgy, and Exploration (SME): Englewood, CO, USA, 2009; pp. 249–268. [Google Scholar]
  152. Pujades, E.; Orban, P.; Bodeux, S.; Archambeau, P.; Erpicum, S.; Dassargues, A. Underground Pumped Storage Hydropower Plants Using Open Pit Mines: How Do Groundwater Exchanges Influence the Efficiency? Appl. Energy 2017, 190, 135–146. [Google Scholar] [CrossRef]
  153. Wessel, M.; Madlener, R.; Hilgers, C. Economic Feasibility of Semi-Underground Pumped Storage Hydropower Plants in Open-Pit Mines. Energies 2020, 13, 4178. [Google Scholar] [CrossRef]
  154. Krassakis, P.; Karavias, A.; Zygouri, E.; Roumpos, C.; Louloudis, G.; Pyrgaki, K.; Koukouzas, N.; Kempka, T.; Karapanos, D. Gis-Based Assessment of Hybrid Pumped Hydro Storage as a Potential Solution for the Clean Energy Transition: The Case of the Kardia Lignite Mine, Western Greece. Sensors 2023, 23, 593. [Google Scholar] [CrossRef]
  155. Blakers, A. Big Battery Plans for Pilbara Ignore Massive Pumped-Hydro Potential. Renew Economy 2022. Available online: https://reneweconomy.com.au/big-battery-plans-for-pilbara-ignore-massive-pumped-hydro-potential/ (accessed on 8 September 2024).
  156. McCullough, C.D.; Schultze, M.; Vandenberg, J. Realising Beneficial End Uses from Abandoned Pit Lakes. Minerals 2020, 10, 133. [Google Scholar] [CrossRef]
  157. Kumar, N.R.; McCullough, C.D.; Lund, M.A.; Newport, M. Sourcing Organic Materials for Pit Lake Remediation in Remote Mining Regions. Mine Water Environ. 2011, 30, 296–301. [Google Scholar] [CrossRef]
  158. Kumar, R.N.; McCullough, C.D.; Lund, M.A. Water Resources in Australian Mine Pit Lakes. Min. Technol. 2009, 118, 205–211. [Google Scholar] [CrossRef]
  159. Cooper, T.F.; Heyes, J.L.; Hightower, O.D. Piloting a Smart Transition to a Post-Closure Working Landscape in Australia. In Proceedings of the International Mine Closure 2020 Congress, Online, 7–11 September 2020. [Google Scholar]
  160. Curtin University; RFF Pty Ltd.; Winyama Pty Ltd. Pilbara Water Resources Situational Analysis; Curtin University: Perth, Australia, 2022; p. 22. [Google Scholar]
  161. Murphy, D.P.; Fromm, J.; Bairstow, R.; Meunier, D. A Repurposing Framework for Alignment of Regional Development and Mine Closure. In Mine Closure 2019: Proceedings of the 13th International Conference on Mine Closure; Fourie, A.B., Tibbett, M., Eds.; Australian Centre for Geomechanics: Perth, Australia, 2019; pp. 789–802. [Google Scholar]
  162. Kragt, M.E.; Lison, C.; Manero, A.; Hawkins, J. Mine Site Rehabilitation Conditions in Western Australia. In Proceedings of the Mine Closure 2019: Proceedings of the 13th International Conference on Mine Closure, Perth, Australia, 3–5 September 2019. [Google Scholar]
  163. McCullough, C.D.; Schultze, M.; Vandenberg, J. Realising Beneficial End Uses for Pit Lakes. In Proceedings of the International Mine Closure 2018 Congress, Leipzig, Germany, 3–7 September 2018. [Google Scholar]
  164. Louloudis, G.; Roumpos, C.; Louloudis, E.; Mertiri, E.; Kasfikis, G. Repurposing of a Closed Surface Coal Mine with Respect to Pit Lake Development. Water 2022, 14, 3558. [Google Scholar] [CrossRef]
  165. Williams, M.S.; Oyedotun, T.D.T.; Simmons, D.A. Assessment of Water Quality of Lakes Used for Recreational Purposes in Abandoned Mines of Linden, Guyana. Geol. Ecol. Landsc. 2020, 4, 269–281. [Google Scholar] [CrossRef]
  166. Mhlongo, S.E.; Amponsah-Dacosta, F. Rehabilitation of Abandoned Open Excavation for Beneficial Use of the Pit Lake at Nyala Magnesite Mine. Int. J. Environ. Res. 2015, 9, 303–308. [Google Scholar]
  167. Soni, A.; Mishra, B.; Singh, S. Pit Lakes as an End Use of Mining: A Review. J. Min. Environ. 2014, 5, 99–111. [Google Scholar]
  168. Swanson, S. What Type of Lake Do We Want? Stakeholder Engagement in Planning for Beneficial End Uses of Pit Lakes. In Mine Pit Lakes: Closure and Management; McCullough, C.D., Ed.; Australian Centre for Geomechanics: Perth, Australia, 2011; pp. 29–42. [Google Scholar]
  169. Proctor, H.; Grigg, A. Aquatic Macroinvertebrates in Final Void Water Bodies at an Open-Cut Coal Mine in Central Queensland. Aust. J. Entomol. 2006, 45, 107–121. [Google Scholar] [CrossRef]
  170. Larranãga, S.; McCullough, C.D.; Lund, M.A. Aquatic Macroinvertebrate Communities of Acid Pit Lakes. In Proceedings of the 31st Congress of the International Association of Theoretical and Applied Limnology, Cape Town, South Africa, 12–18 August 2010. [Google Scholar]
  171. Lund, M.; van Etten, E.; Polifka, J.; Vasquez, M.Q.; Ramessur, R.; Yangzom, D.; Melanie, L. Blanchette. The Importance of Catchments to Mine-Pit Lakes: Implications for Closure. Mine Water Environ. 2020, 39, 572–588. [Google Scholar] [CrossRef]
  172. Richardson, D.; Bourke, G.; Swart, P. Aquatic Biodiversity Values of Two Non-Acidic Pit Lakes Created by Open-Cut Coal Mining. In Proceedings of the Life of Mine, Brisbane, Australia, 28–30 April 2021. [Google Scholar]
  173. Luek, A.; Rasmussen, J.B. Chemical, Physical, and Biological Factors Shape Littoral Invertebrate Community Structure in Coal-Mining End-Pit Lakes. Environ. Manag. 2017, 59, 652–664. [Google Scholar] [CrossRef]
  174. Bylak, A.; Rak, W.; Wójcik, M.; Kukuła, E.; Kukuła, K. Analysis of Macrobenthic Communities in a Post-Mining Sulphur Pit Lake (Poland). Mine Water Environ. 2019, 38, 536–550. [Google Scholar] [CrossRef]
  175. Gajardo, G.; Redón, S. Hypersaline Lagoons from Chile, the Southern Edge of the World. In Lagoon Environments around the World—A Scientific Perspective; IntechOpen: London, UK, 2019. [Google Scholar]
  176. Hammer, U.T. Saline Lake Ecosystems of the World; Junk: Dordrecht, The Netherlands, 1986. [Google Scholar]
  177. Timms, B. Study of the Saline Lakes of the Esperance Hinterland, Western Australia, with Special Reference to the Roles of Acidity and Episodicity. Nat. Resour. Environ. Issues 2009, 15, 44. [Google Scholar]
  178. Hart, E.A.; Lovvorn, J.R. Lovvorn. Interpreting Stable Isotopes from Macroinvertebrate Foodwebs in Saline Wetlands. Limnol. Oceanogr. 2002, 47, 580–584. [Google Scholar] [CrossRef]
  179. Sampson, J.R.; Mellott, R.S.; Pastorok, R.A. Ecological Risk Assessment for a Mine Pit Lake, Nevada, USA. In Proceedings of the British Columbia Mine Reclamation Symposium 1996, Dawson Creek, BC, Canada, 14–17 September 1996. [Google Scholar]
  180. Miller, L.L.; Rasmussen, J.B.; Palace, V.P.; Sterling, G.; Hontela, A. Selenium Bioaccumulation in Stocked Fish as an Indicator of Fishery Potential in Pit Lakes on Reclaimed Coal Mines in Alberta, Canada. Environ. Manag. 2013, 52, 72–84. [Google Scholar] [CrossRef]
  181. Holcombe, S.; Elliott, V.; Keeling, A.; Berryman, M.; Hall, R.; Ngaamo, R.; Beckett, C.; Moon, W.; Hudson, M.; Kusabs, N.; et al. Indigenous Exchange Forum: Transitions in Mine Closure; Centre for Social Responsibility in mining, University of Queensland: Brisbane, Australia, 2022. [Google Scholar]
  182. Holcombe, S. Sustainable Aboriginal Livelihoods and the Pilbara Mining Boom. In Indigenous Participation in Australian Economies: Historical and Anthropological Perspectives; Keen, I., Ed.; ANU Press: Canberra, Australia, 2010; pp. 141–164. [Google Scholar]
  183. McCullough, C.D. (Ed.) Mine Pit Lakes: Closure and Management; Australian Centre for Geomechanics (ACG): Perth, Australia, 2011. [Google Scholar]
Figure 1. Main map: generalised location of the Pilbara mining region in Western Australia. Inset: locations of major Pilbara mines (◾iron ore, ▲ gold, ▼ specialty metal, and ⯁ steel alloy metal). Fortescue River drainage channels.
Figure 1. Main map: generalised location of the Pilbara mining region in Western Australia. Inset: locations of major Pilbara mines (◾iron ore, ▲ gold, ▼ specialty metal, and ⯁ steel alloy metal). Fortescue River drainage channels.
Mining 04 00048 g001
Figure 2. Mt Goldsworthy pit lake still filling in 2000 (photo: Hugh Jones).
Figure 2. Mt Goldsworthy pit lake still filling in 2000 (photo: Hugh Jones).
Mining 04 00048 g002
Figure 3. Conceptual water balances of Pilbara pit lakes. From top: terminal, throughflow, and flowthrough.
Figure 3. Conceptual water balances of Pilbara pit lakes. From top: terminal, throughflow, and flowthrough.
Mining 04 00048 g003
Figure 4. Solute sources for Pilbara pit lakes.
Figure 4. Solute sources for Pilbara pit lakes.
Mining 04 00048 g004
Figure 5. Conceptual long-term water quality evolution for terminal water balance in Pilbara pit lakes.
Figure 5. Conceptual long-term water quality evolution for terminal water balance in Pilbara pit lakes.
Mining 04 00048 g005
Figure 6. Backfill above water table influences on down-gradient groundwater quality.
Figure 6. Backfill above water table influences on down-gradient groundwater quality.
Mining 04 00048 g006
Figure 7. Conceptual model of long-term density-driven saline seepage potential in Pilbara hypersaline pit lakes.
Figure 7. Conceptual model of long-term density-driven saline seepage potential in Pilbara hypersaline pit lakes.
Mining 04 00048 g007
Figure 8. Potential PMLU opportunities for saline and freshwater Pilbara pit lakes.
Figure 8. Potential PMLU opportunities for saline and freshwater Pilbara pit lakes.
Mining 04 00048 g008
Table 1. Potential hazards for consideration in closure planning of BWT voids in the Pilbara.
Table 1. Potential hazards for consideration in closure planning of BWT voids in the Pilbara.
HazardDescription
Creek captureSeasonal flow events are often of great magnitude and, with many pits located within or near floodplains, creeks may flow into pit voids, leading to pit wall destabilisation and erosion, as well as reduced or even intercepted downstream flows.
Impact of groundwater lossPit lakes are likely to evaporate annually far more water than is accumulated from seasonal rainfall events, leading to constant abstraction of regional groundwaters as a terminal evaporative sink.
Contact and drinkingVery poor, e.g., acidic, pit lake water quality can have acute effects on humans and wildlife in contact with pit lake waters, including on individuals drinking from the lake.
Discharge to creekOvertopping of lowest pit walls may occur during storm events where pit lakes waters are then discharged to lower waterway reaches, transporting geochemical contaminants to downstream receiving environments.
Seepage to groundwaterPit lake water may seep to groundwater where the pit intercepts regional flow paths and/or becomes surcharged through storm event precipitation or creek capture. Seepage water quality may be poor through geochemical interactions with pit void/backfill materials and also evapoconcentration. Longer term, density-driven seepage may result if pit lake salinity leads to water densities that exceed groundwater head differences to the lake, potentially reversing flow away from the lake.
Pests and diseasesExotic aquatic species may use pit lakes as habitat. Feral terrestrial species and birds may drink from pit lakes.
SafetySteep sided and unstable pit highwalls can present fall risks. Steep beach angles can lead to drownings.
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

McCullough, C.D. Below Water Table Mining, Pit Lake Formation, and Management Considerations for the Pilbara Mining Region of Western Australia. Mining 2024, 4, 863-888. https://doi.org/10.3390/mining4040048

AMA Style

McCullough CD. Below Water Table Mining, Pit Lake Formation, and Management Considerations for the Pilbara Mining Region of Western Australia. Mining. 2024; 4(4):863-888. https://doi.org/10.3390/mining4040048

Chicago/Turabian Style

McCullough, Cherie D. 2024. "Below Water Table Mining, Pit Lake Formation, and Management Considerations for the Pilbara Mining Region of Western Australia" Mining 4, no. 4: 863-888. https://doi.org/10.3390/mining4040048

APA Style

McCullough, C. D. (2024). Below Water Table Mining, Pit Lake Formation, and Management Considerations for the Pilbara Mining Region of Western Australia. Mining, 4(4), 863-888. https://doi.org/10.3390/mining4040048

Article Metrics

Back to TopTop