Groundwater Resource Investigations for Sydney's Water Supply at Leonay, Western Sydney, NSW

摘要

The NSW government recognize that groundwater within the Sydney Basin is a valuable resource, however, despite its proximity to Australia's largest urban population, remarkably little groundwater resource investigative work of the deep sandstone aquifers has been conducted until the 21st century. One of the drought management strategies originally proposed with the 2004 and 2006 Metropolitan Water Plans was to investigate the possible use of groundwater reserves surrounding Sydney during periods of severe drought. Seven priority sites were selected by the Sydney Catchment Authority (SCA) with Leonay in western Sydney one of these priority sites. Following encouraging results from a preliminary groundwater investigation, a second more extensive, groundwater resource investigation commenced in November 2006 to quantify the groundwater resource potential of developing the Hawkesbury Sandstone aquifers in western Sydney. The program consisted of drilling eight production bores and 10 observation bores, at seven locations in the Leonay-Emu Plains area. These boreholes fully and partially penetrate the Hawkesbury Sandstone, to assess aquifer parameters, resource potential, possible interaction between surface water (Nepean River) and groundwater, and recharge/discharge characteristics. A number of multidisciplinary approaches have been undertaken to characterise the groundwater resource and to quantify potential extraction rates. These approaches include a 60 day pumping trial, multiple pumping tests using a variety of test pumping analytical techniques to interpret the test pumping data, and collection of groundwater for isotope analysis to assess recharge mechanisms and groundwater residence times. Throughout these investigations the individual bore yields and groundwater quality were encouraging. The scientific data collected will form the basis for assessing resource potential assessment and groundwater recharge/discharge characteristics. Aquifer hydraulic parameters are to be calculated from the test pumping analysis and these results will be used to develop a groundwater model to assess the sustainability of this resource. The investigation has been invaluable in adding to our hydrogeological knowledge of deep sandstone aquifers within the Sydney Basin which until recently had been poorly understood.