Oral Presentation Australasian Groundwater Conference 2017

Arrow Energy Pty Ltd (Arrow), as part of its Federal environmental approval conditions for its proposed Surat Gas Project, is required to undertake assessments of the potential impact to groundwater dependent ecosystems (GDEs) as a result of potential aquifer drawdown and associated reduced groundwater availability.  To address these conditions, Arrow has adopted the Model – Investigate – Verify – Manage framework to assessing potential impacts distal from coal seam gas (CSG) operations. 

Arrow commissioned the development of a numerical surface water-groundwater model to identify any potential impact to GDEs from groundwater drawdown as a result of its proposed operations.  The model indicated that the potential impact is immeasurable (mm/annum) compared to background variations (cm/day to m/annum). 

Arrow proposes to undertake investigations to confirm the status of potential GDEs identified through a risk assessment.  These potential GDEs were selected using a GDE likelihood matrix based on:

• depth to groundwater data,
• vegetation mapping and site observations,
• landscape position (hydrology/geomorphology),
• ecosystem ability to adapt to changes in groundwater availability,
• the scale of the impact in the watertable aquifer.

The investigation options currently being assessed include:

• undertaking a drilling program to identify local lithology/stratigraphy,
• monitoring for seasonal groundwater level/water quality variations,
• connectivity studies of the water table aquifer and underlying aquifers, and
• use of leaf water potential and soil water potential, in combination with stable isotopes of water to determine the depth at which vegetation is accessing water.

A GDE monitoring program will then be developed based on the outcomes of the investigations and model verification which may include ongoing groundwater and ecological monitoring.