In 2007, the Sydney Catchment Authority (SCA) contracted PB to conduct research in the Upper Nepean Catchment, approximately 100 km south-west of Sydney. The project was to research surface water – groundwater interactions and groundwater flow in a fractured rock aquifer system. The system had been identified as a possible source of potable water for Sydney, and SCA wanted to assess whether a sustainable borefield could be developed. The area in question is an important catchment for the Nepean and Avon dams and is subject to substantial water transfer volumes from the Shoalhaven Scheme through to Warragamba Dam. Numerous surrounding farms use local creeks, springs and bores. Therefore, SCA wanted to assess the sustainability of groundwater extractions in the area, and quantify the impacts on creek flow if part of a large borefield was developed there.

Working closely with Dr Craig Divine from consulting firm Arcadis, PB staff developed a research program to investigate connections between the aquifer and the region’s surface water systems. These investigations used gas- and dye-applied tracers, and subsequent numerical modelling, during a 60-day pump test. Ten staff were involved in the project, which required extensive stakeholder liaison and meticulous planning.

The research found that water-flows through rock fractures are particularly important in assessing borefield feasibility and optimisation, including the best locations and spacing of bores. The findings regarding the impact of fracture properties are internationally significant, and peer-reviewed papers have been published based on data from the project. The trends observed in the Upper Nepean can also be extrapolated to other streams in the Sydney Basin.

The project is scheduled to finish by late 2008.

Awards

2008: NSW Water Research Merit Award, from the Australian Water Association