Abstract
Estimation of natural recharge and potential for seawater intrusion are critical considerations for management of coastal freshwater aquifers. We show hydrochemical signatures of groundwater to identify the influence of geological control on chemical processes in a coastal groundwater system. We used dominant hydrochemical facies, salinity and magnesium ions to determine two main groundwater flow paths with different origins and ages. Mixing of groundwater with different origins and ages results in unreliable recharge estimates using chlorofluorocarbon (CFC) and chloride mass balance (CMB) methods, thus limiting available methods for recharge assessment. Interpretation of hydrochemical data suggests that calcium carbonate dissolution, ion exchange processes and mixing with sea aerosol in coastal zones are the main influencing factors on groundwater chemistry. Restricted groundwater flows due to occurrence of a basement high at the southern side of the basin boundary influence the distance to the toe of the saline wedge. Thus, knowledge of geological control over groundwater systems forms an important part of characterising basins and contributes toward effective management of groundwater resources.
Highlights
Spatial distribution of groundwater chemistry is primarily influenced by mineralogical composition of sediments in contact with groundwater [1]
We examined effects of basement rock outcrop and discontinuity of the clay aquitard on groundwater salinity, water chemistry, influence on recharge estimation methods and extent of the saline wedge in a coastal aquifer in South Australia
The influence of geological control is divided into three sections: influence on QL aquifer salinity, hydrochemistry of QL groundwater, and the effect of extension of the saline wedge in Tertiary Sand (TS) aquifer
Summary
Spatial distribution of groundwater chemistry is primarily influenced by mineralogical composition of sediments in contact with groundwater [1]. The influence of geological control changes natural water chemistry and knowledge of main hydrochemical processes that control groundwater chemistry is a prerequisite for effective basin management [2]. Several studies examined the influence of geological controls: the presence of faults [3,4]; geology and structure of bedrock [5,6]; fracture control [7] which influences groundwater flow and water chemistry; and hydrogeological study of. The presence of faults and their influence on flow paths and water chemistry are widely reported and these are known to be effective flow barriers [3]. Eaton et al [7] noted that there are few studies on the hydrogeology of sedimentary rock aquitards, they are important controls in regional ground water flow systems. We examined effects of basement rock outcrop and discontinuity of the clay aquitard on groundwater salinity, water chemistry, influence on recharge estimation methods and extent of the saline wedge in a coastal aquifer in South Australia
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
