3.5 Impacts on and risks to water-dependent assets

Summary

Ecological water-dependent assets

Of the 3982 ecological assets in the Galilee subregion’s register of water-dependent assets, 241 are in the zone of potential hydrological change. The location of assets, including the potential distribution of various species, was determined at a single point-in-time when the asset register was established. Asset locations were not continually updated throughout this bioregional assessment (BA).

All of the 241 assets within the zone intersect with one or more of the potentially impacted landscape groups, and 65 of these assets are confined entirely to the zone. The 3741 ecological assets outside the zone are considered to be very unlikely (less than a 5% chance) to be impacted by modelled additional coal resource development in the Galilee subregion.

Of the 241 ecological assets in the zone, 148 meet criteria for potential hydrological impacts that place them ‘more at risk of hydrological changes’ due to additional coal resource development. That is, all or part of the area of these assets occurs within one or more of the potentially impacted landscape groups and there is a greater than 50% chance of the modelled hydrological change exceeding the defined threshold in one or more of the hydrological response variable(s) relevant to the landscape group(s).

The ‘more at risk of hydrological changes’ assets include 106 groundwater-dependent ecosystems. Also among the ‘more at risk’ assets are potential habitat for 12 threatened species listed under the Commonwealth’s Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act), 2 EPBC Act-listed threatened ecological communities, 7 regional ecosystems listed under Queensland’s Nature Conservation Act 1992 and 4 parks and reserves.

A concentration of ecological assets occurs in the ‘Springs’ landscape group. Although the 200 springs in this landscape group occupy less than 1% of the area of the zone of potential hydrological change, 48 ecological assets (20% of all ecological assets in the zone) intersect with it, including 16 that are confined entirely to the zone. Doongmabulla Springs complex is the location where most of these assets occur, and they include the springs themselves, the Doongmabulla Mound Springs Nature Refuge, habitat (potential distribution) of an EPBC Act-listed threatened ecological community – ‘The community of native species dependent on natural discharge of groundwater from the Great Artesian Basin’ – and habitat (potential species distribution) of two EPBC Act-listed threatened plant species.

The majority of available evidence indicates that the groundwater source for the assets associated with the Doongmabulla Springs complex is primarily the Clematis Group aquifer. Two alternative groundwater model conceptualisations applied in this BA predict that 181 of the 187 springs in the Doongmabulla Springs complex have a 5% chance of experiencing additional groundwater drawdown in excess of 0.2 m. Consideration of multiple lines of evidence – including signed digraphs, qualitative mathematical models, interpretation of various products derived from archived Landsat imagery and expert ecological knowledge of the threatened plant species – indicates that this level of drawdown will impact the ecological functioning of some ecological assets; however, there will be considerable variation in response across springs and spring complexes.

Economic water-dependent assets

There are 129 economic water-dependent assets within the Galilee assessment extent, all of which are classed as either water access rights or basic water rights (stock and domestic). Of these, 96 are associated with groundwater management areas and 33 with surface water management areas. Each asset consists of a variable number of asset ‘elements’, which are typically individual groundwater bores or surface water extraction points.

The hydrological changes due to the seven coal mines modelled for the BA of the Galilee subregion will potentially impact six of these water-dependent economic assets, comprising five groundwater assets and one surface water asset. The surface water asset is a basic water right under the Burdekin River water resource plan, and has three separate water extraction points (elements) within the zone of potential hydrological change. Two of these asset elements are on the Belyando River, and another is on the headwater tributary of Native Companion Creek. The nearest BA surface water modelling nodes to these three extraction points indicate that it is very unlikely (less than 5% chance) that this surface water asset will experience reductions in annual flow volume greater than 1.5%. However, there are a wide range of modelled increases in the number of zero-flow days that may affect this asset, with several locations modelled to exceed increases of 250 zero-flow days per year (at the 95th percentile of all modelling results).

Three of the groundwater economic assets potentially impacted due to additional coal resource development are associated with the Clematis Group aquifer, and are managed as part of the Water Plan (Great Artesian Basin) 2006 (although this plan was superseded in September 2017). These include a basic water right (stock and domestic) and a water access right in the Barcaldine North 3 Groundwater Management Unit, and a basic water right in the Barcaldine East 4 Groundwater Management Unit. Of the 92 individual groundwater bores in Barcaldine East 4 that are in the Galilee assessment extent, it is very likely (greater than 95% chance) that 5 bores will experience between 0.2 and 2 m of drawdown, and very unlikely that more than 22 bores will be affected by this level of drawdown. Similarly, for the 162 bores in the assessment extent associated with the basic water right in Barcaldine North 3, the number of bores modelled to experience between 0.2 to 2 m of drawdown varies from 7 bores (5th percentile) to 93 bores (95th percentile). However, it is very unlikely that the maximum drawdown that will affect any of the bores associated with these three groundwater economic assets will exceed 1.5 m.

Two other groundwater economic assets in the asset register are likely to be impacted by drawdown associated with the seven coal mines in the modelled coal resource development pathway (CRDP). These are a water access right and a basic water right that are unassigned to a particular management subgroup (for BA purposes). The 15 individual bores associated with the unassigned water access right occur in three main clusters (and may source water from different aquifers), including near the towns of Jericho and Alpha (i.e. their respective town water supply bores). Of the four bores that source water from the Clematis Group aquifer near Jericho, drawdowns of between 0.2 and 2 m are modelled at the 50th and 95th percentiles, although the maximum amount of drawdown is less than 1 m for all results. Potential impacts for many of the bores near Alpha cannot be quantified due to limitations of the groundwater modelling approach, and thus remain a key knowledge gap.

The list of groundwater economic assets compiled for this BA was not exhaustive, and many bores known from the Queensland bore database were not included (for various reasons) in the water-dependent asset register. There are approximately 105 such bores within the zone of potential hydrological change that are interpreted to source water from the near-surface unconfined aquifer (Quaternary alluvium and other Cenozoic sediments). However, 26 of these are company-owned monitoring bores, 6 others are known to be ‘abandoned and destroyed’ and 3 bores occur in the mine exclusion zone. Of the remaining bores analysed here, it is very likely that 7 will experience at least 0.2 m of drawdown, and very unlikely that more than 52 bores will be affected by this level of drawdown. Drawdowns of greater than 2 m are modelled to affect between 2 and 13 bores (at the 5th and 95th percentiles, respectively), which may trigger the need for ‘make good’ provisions to be negotiated.

A further 31 bores near the central-eastern margin of the Galilee subregion source groundwater from the Clematis Group aquifer but are not in the asset register (this also excludes some company monitoring bores). The maximum modelled drawdown for these bores is about 1 m. Under Queensland’s Water Act 2000, 5 m of drawdown may trigger the need for ‘make good’ provisions in consolidated rock aquifers. There are also 34 non-company bores within the zone of potential hydrological change that tap the upper Permian coal measures, the main coal mining (and dewatering) target layer in the Galilee Basin. Based on the results from the analytic element model (AEM) for the Galilee subregion (which uses a simplified conceptualisation of the regional hydrogeology), most of these bores are predicted to experience drawdown in excess of 20 m.

Sociocultural assets

Of the 151 sociocultural assets in the Galilee assessment extent, only four partially intersect with the zone of potential hydrological change. Three of these assets were nominated from the Register of the National Estate, including Doongmabulla Springs (natural indicative place), Lake Buchanan and catchment (natural registered place) and the Old Bowen Downs Road (historic indicative place). Consultation with several local Indigenous groups in the Galilee subregion identified 24 species of fauna and flora that are of critical cultural heritage value, all of which may be water dependent. However, as there was no spatial information associated with these Indigenous assets it was not possible to determine if they occur within the zone of potential hydrological change.