2.5 Water balance assessment

These products use results from surface water and groundwater numerical modelling to assess how water balances might be different as a result of coal resource development in the subregion or bioregion for three time periods: 2013 to 2042, 2043 to 2072, and 2073 to 2102.

 Water balances are reported for the two futures considered in a bioregional assessment:

• baseline coal resource development (baseline): a future that includes all coal mines and coal seam gas fields that were commercially producing as at December 2012
• coal resource development pathway (CRDP): a future that includes all coal mines and coal seam gas fields that are in the baseline as well as those that were expected to begin commercial production after December 2012.

The difference in results between these potential futures is due to the additional coal resource development – all coal mines and coal seam gas fields, including expansions of baseline operations, that were expected to begin commercial production after December 2012.

The exact set of water balance terms reported varies from region to region. Factors considered in the surface water balance assessments generally include rainfall, surface water outflow, licensed extraction and change in storage. Factors considered in the groundwater balance assessments generally include groundwater recharge, evapotranspiration, baseflow, upward flow from deeper groundwater and changes in storage.

Relationship to other products

The water balance reported here summarises volumetric changes and does not represent impacts on flow regime changes which may be more significant than changes in absolute flow volumes in some cases. For more details see surface water numerical modelling (product 2.6.1) and groundwater numerical modelling (product 2.6.2).

Impacts of flow volume and regime changes are considered in impact and risk analysis (product 3-4), which examines the risks to, and potential impacts on, water resources and water-dependent assets due to coal seam gas or coal mining developments.