2.1.6 Water management for coal resource developments


The surface water and groundwater numerical models require data on impacted areas, depths of mine workings, water extractions and discharge rules to quantify the hydrological impacts of mine developments. These data have been sourced primarily from mining company documents and state agency datasets. Details of the source data and the methods used to generate datasets for input into the models are presented in this section.

The objective of groundwater and surface water modelling in bioregional assessments is to quantify the cumulative impacts of coal resource developments on regional hydrology. In Section 2.3.5 of companion product 2.3 for the Hunter subregion (Dawes et al., 2018), four causal pathway groups are identified that potentially link hydrological changes from mining developments to water-dependent assets in the wider region. These causal pathway groups are subsurface depressurisation and dewatering, subsurface physical flow paths, surface water drainage and operational water management. The models require information on the location and magnitude of hydrological changes at each mine site to quantify the changes on and off the site via these causal pathways.

The Australian Water Resources Assessment (AWRA) landscape water balance model (AWRA-L) requires a time series of the mine site footprint area for each mining operation, where the footprint includes all disturbed surface areas – including the open-cut pits, areas above longwall panels, roads, spoil dumps, water storages and infrastructure – as well as undisturbed areas from which runoff is captured by water storages. Except for the footprint areas above longwall mine panels, the model assumes all runoff generated from the footprint area is retained on site. For the mine footprints above longwall mines, the model assumes that there is some interception of runoff as a consequence of subsidence (see companion product 2.6.1 (surface water numerical modelling) for the Hunter subregion (Zhang et al., 2018)).

While a mine’s footprint is known to vary over the life of the mine, a constant footprint was used in the groundwater modelling, broadly corresponding to the maximum footprint. Variations in time are represented through a changing annual flow rate, rather than a time-varying footprint. Each mine complex may have many individual mine workings. Mine workings are individual pits, or clusters of pits, or groups of longwall panels that mine the same seam, or a bord-and-pillar area, defined by availability of geometry and flow rate data. Given the coarse resolution of the regional-scale groundwater model (minimum pixel area of ~500 m), the finer details of individual roadways, chain pillars, bords, etc. are not represented in the model. In most areas, even individual longwall panels are not resolved. The depth of the footprint is the lowest depth of excavation for the mine workings, which could be the bottom of the open-cut pit, the deepest longwall panel, or the deepest bord-and-pillar section. Details on representation of mine footprints in the groundwater model can be found in Section of companion product 2.6.2 for the Hunter subregion (Herron et al., 2018).

The river model (AWRA-R) requires data on extractions from the river for both mining and non-mining uses. It also represents licensed discharges to the stream. Section 2.1.4 details data and methods for representing licensed extractions and discharge rules in the river in the model.

Key sources of mine water management information are the mining companies and state agencies. In particular, mining companies prepare a range of reports as part of the mining approvals process and subsequent management, monitoring and reporting processes. These include annual environmental management reports, annual reviews, briefing papers, conditions of approval, Director-General’s or Secretary’s environmental assessment reports, environmental impact statements (EIS), groundwater monitoring program reports, mine plan reviews, mining operations plans, subsidence management plans and water management plans. These reports can be obtained from either or both of the mining company and the NSW Planning and Environment’s Major Projects Assessments websites. These reports were searched for information to inform both surface water and groundwater modelling.

This section provides details of the data used in the numerical models to represent mine water management, including the sources of data, quality and quantity of data and the steps undertaken to derive datasets for input into the models. Table 16 lists the relevant datasets, identifies which model uses them, the relevant causal pathway group and the relevant section of this product. Water management plans referred to as sources of information for representing mine water management in the numerical models are listed in the references list at the end of this section.

A number of additional coal resource developments were not modelled by the groundwater and/or surface water models (see Section 2.3.4 of companion product 2.3 for the Hunter subregion (Dawes et al., 2018)). Therefore details relevant to modelling these mines are not included in this section. The potential impacts from these developments will be considered qualitatively in companion product 3-4 for the Hunter subregion (as listed in Table 2).

Table 16 Datasets used to represent mine water management in hydrological modelling for the Hunter subregion



Causal pathway group


Surface water mine footprints

Surface water – AWRA-L

Surface water drainage

Groundwater mine footprints


Subsurface depressurisation and dewatering;

Subsurface physical flow paths

Groundwater flow rates (mine water make)


Subsurface depressurisation and dewatering

River and alluvial water source extractions

Surface water – AWRA-R

Operational water management

Mine discharges to rivers

Surface water – AWRA-R

Operational water management

Last updated:
18 January 2019
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