The proposed Snowy 2.0 project is a 2,000 megawatt pumped hydro scheme with capacity for 175 hours of storage. Snowy 2.0 will connect the Talbingo and Tantangara Reservoirs in the Kosciuszko National Park via an underground tunnel of approximately 30 km. A power station located almost 1 km underground will harness energy from water flowing from Tantangara Reservoir (approximately 1,215 mAHD) to Talbingo Reservoir (approximately 540 mAHD) to create electricity. When there is excess energy in the National Energy Market, the power station will operate in reverse, pumping water up to Tantangara Reservoir to be stored.
Several environmental assets that may be sensitive to groundwater impacts of the project have been identified. These include the Yarrangobilly Caves 8 km north of the project, a number of rivers and creeks under which the power waterway tunnel will be excavated and a number of alpine bogs and fens. A groundwater assessment is being undertaken to identify the risks and appropriate management measures.
Characterisation of the groundwater system and subsequent impact assessment for the project has involved conducting investigations in a challenging environment. Surface disturbance has been controlled to minimise impacts on the flora and fauna of the Kosciuszko National Park which, for months of the year, is covered in snow. Further, prior to the commencement of investigations for Snowy 2.0, there were no groundwater bores in the project area.
Characterisation of the groundwater system has involved collaborative efforts from a number of teams employing a variety of techniques including drilling of numerous bores, primarily along the power waterway tunnel alignment, to identify geological, geotechnical and hydrogeological properties, a range of downhole and ground surface-based geophysical surveys, slug tests and pumping tests, groundwater and surface water chemical sampling, stream flow gauging and isotopic analysis to identify water sources and pathways.
The combination of surface and groundwater chemistry, water balance and baseflow analyses indicate high recharge from rainfall, on the order of 30 percent of rainfall. Hydraulic testing has indicated hydraulic conductivities vary orders of magnitude across the project area.
A MODFLOW-USG numerical groundwater model, capable of representing the fine detail of, and high vertical hydraulic gradients around, a complex interconnection of numerous underground tunnels, shafts and caverns as well as the large scale of the project has been built to predict groundwater impacts on the groundwater system as well as informing design of groundwater control measures.