2.6.1.2 Review of existing models

Summary

Mining companies undertake assessments of the impacts on surface water from mining developments as part of their approvals process. These assessments use models to determine risks from local effects such as erosion, flooding and ponding, and to quantify components of the mine site water balance. The models are local scale and address local issues that are not within the scope of the bioregional assessments. A review of these models has not been undertaken.

There is one regional scale surface water modelling system in regular use in the Hunter subregion: the Hunter Integrated Quantity-Quality Model (IQQM). It is used by the NSW Department of Primary Industries primarily to inform water resources planning and management. With further development, it could be made suitable for a bioregional assessment, but proprietary issues meant this was not an option. Instead, the Australian Water Resources Assessment (AWRA) landscape model (AWRA-L) and AWRA river model (AWRA-R) have been adopted for the Bioregional Assessment Programme.

Time series of outputs from the Hunter IQQM, including volume of water stored in reservoirs, reservoir releases and surface water diversions, have been used to develop and calibrate the AWRA-R model, in order to simulate the change in hydrological effects of baseline and coal resource development pathway in the Hunter subregion.

As part of their approvals process, mining companies are required to undertake environmental assessments to evaluate the potential effects on the environment from mining and inform monitoring and mitigation strategies. An assessment of the potential impacts on surface water form part of these assessments. In general, the modelling that is undertaken is to investigate things like channel scour; impacts on bank stability; risks of local flooding; and potential drainage issues, such as local ponding; and quantify components of the mine site water balance. The focus of this modelling tends to be local in scale, with a view to minimising off-site impacts through on-site water management. These surface water assessments do not require regional scale river models. A review of the models used for this range of purposes has not been undertaken.

In NSW, the state agency river model is the Integrated Quantity-Quality Model (IQQM) (Simons et al., 1996). IQQMs have been constructed for most river basins in NSW to assist in water resources planning and management, such as determining annual water allocations for the various users (irrigation, electricity generation, town water supply) within water sharing plan areas. They use Sacramento (Burnash et al., 1973) rainfall-runoff models to estimate catchment runoff contributions to the IQQM link-node network. Much of the Hunter subregion is included in the Hunter IQQM (Simons et al., 1996); the Macquarie-Tuggerah lakes basin is not.

The Hunter IQQM represents the inflows and outflows along the regulated river system from Glenbawn Dam to Greta. It simulates, amongst other things, streamflows, volume of water stored in reservoirs, reservoir releases and surface water diversions. It has not been specifically constructed to model the impacts of coal resource developments on streamflow, and cannot be used for a bioregional assessment in its current form, although, at considerable effort, it could be customised to do so. However, proprietary issues also meant that the Hunter IQQM was not an option for the bioregional assessment for the Hunter subregion. Instead, NSW DPI Water generously agreed to assist the bioregional assessment hydrologists to incorporate some components of its implementation in the Hunter Australian Water Resources Assessment (AWRA) river model (AWRA-R) built for the assessment for the Hunter subregion. These include:

  • time series of surface water diversions to represent current demands on water resources
  • time series of the volume of water stored in reservoirs and reservoir releases

and pertain to the Water Sharing Plan for the Hunter Regulated River which commenced in 2004 and the development and licensing conditions in 2012. Details of how these IQQM datasets are used in calibrating the AWRA-R model are given in Section 2.6.1.4 .

The AWRA landscape model (AWRA-L) and AWRA-R have been adopted for the Bioregional Assessment Programme. AWRA-L is a grid-based model which can represent the spatial variability in physical attributes that influence catchment runoff over time. The AWRA-R model is a link-node model that can receive inputs (e.g. inflows from AWRA-L; groundwater contributions from a groundwater model; dam releases; diversions from the river; discharges to river) and propagate those changes through the river network. Readers are referred to companion submethodology M06 (Viney, 2016) for further details.

Last updated:
15 June 2018
Thumbnail of the Hunter subregion

Product Finalisation date

2018

ASSESSMENT