Hydrogeologic and 3-D Shallow Groundwater Flow Integrated Study and Salinisation Processes with Some Areas at Western Sydney, New South Wales, Australia

Abstract

In South Western Sydney (which encompasses the study area), New South Wales, Australia, salinity is a major emerging urban problem and is primarily related to rising groundwater level. This eight-chapter thesis focuses on the factors influencing salinity and its processes in the Mount Annan, Currans Hills and Narellan Vale areas, and investigates both the present three-dimensional (3-D) groundwater flow pattern and that expected to occur in the area as a result of future urban expansion. The chemical and physical analyses carried out on the soil samples collected from the study areas, and the groundwater level and electrical conductivity data have been interpreted in a comprehensive integrated manner to identify factors and processes influencing salinity, and to develop a reliable and detailed hydrogeological conceptual model. A new method has been developed for groundwater recharge estimation for unconfined aquifers under the assumption that groundwater recharge is solely due to rainfall. The method is capable of estimating groundwater recharge and drainage and predicting groundwater levels from time series of observed groundwater level data and rainfall events. The method can produce non-unique solution. Despite the non-uniqueness, the estimated recharges do not suffer large variations. A 3-D groundwater flow model has been developed by calibrating the measured groundwater level data using the MODFLOW code. The groundwater flow maps constructed from the 3-D calibration results have shown that the flow pattern is collectively controlled by topography and recharge, and varies in space and time, which likely suggests that the salinisation process, which is influenced by the lateral and vertical groundwater movements, varies in space and time. Analysis has revealed that future urbanisation likely results in changes in the subsurface water balance. Conclusions and suggested avenues for future research are drawn in Chapter 8.