Sustainability of groundwater extraction for the Pimpama coastal plain, Queensland, Australia.

Abstract

This paper presents results for field scale seawater intrusion simulations along the Pimpama coastal-plain using SALTFLOW. The simulations incorporated groundwater extraction and sea-level-rise, along with a sensitivity analysis for three physical forcings. The three physical forcings studied in the sensitivity analysis included variations in; freshwater inflow, sea-level-rise and groundwater extraction. The field site selected to perform the field scale seawater intrusion simulations was the Pimpama coastal-plain, which is located between Brisbane and the Gold Coast in South-East Queensland (see Figure 1). The region is undergoing significant population growth and is an area of hydrological interest, since groundwater extraction is relied upon to provide water for domestic and agricultural supply. In addition to land use change, further stresses will be placed upon the Pimpama aquifer due to a predicted sea-level rise, whilst population growth should lead to a concomitant rise in groundwater extraction. Whether the extraction of groundwater from the Pimpama aquifer is sustainable for meeting future water use needs is a significant resource supply problem and as yet no attempt has been made to assess the sustainability of groundwater extraction in this area. Thus, the simulations performed in this study represent the first attempt to assess the sustainability of groundwater extraction for the Pimpama coastal-plain, in light of the stresses of sealevel-rise, and a potential seawater intrusion. The SALTFLOW package was selected for the simulation of seawater intrusion for the Pimpama coastal-plain. Preliminary work tested the computational, physical and other modeling attributes for a suite of packages, as well as the performance of each package against benchmark problems from the literature. Ultimately, the SALTFLOW package was selected over PDE2D and SUTRA due to the ease with which time varying boundary conditions for groundwater flow could be incorporated into the model. Use of time varying boundary conditions for groundwater flow enabled the effect of sealevel-rise to be incorporated into the model. The model also considered the effect of groundwater extraction on future groundwater Chloride concentrations for the Pimpama coastal-plain. The field scale simulations suggest that a serious seawater intrusion is predicted to occur near the coastal boundary of the Pimpama coastal-plain over the next twenty years.