Assessing the recharge of a coastal aquifer using physical observations, tritium, groundwater chemistry and modelling

Santos, Isaac R., Zhang, Chenming, Maher, Damien T., Atkins, Marnie L., Holland, Rodney, Morgenstern, Uwe and Li, Ling (2016) Assessing the recharge of a coastal aquifer using physical observations, tritium, groundwater chemistry and modelling. Science of the Total Environment, 580 367-379. doi:10.1016/j.scitotenv.2016.11.181

Author Santos, Isaac R.
Zhang, Chenming
Maher, Damien T.
Atkins, Marnie L.
Holland, Rodney
Morgenstern, Uwe
Li, Ling
Title Assessing the recharge of a coastal aquifer using physical observations, tritium, groundwater chemistry and modelling
Journal name Science of the Total Environment   Check publisher's open access policy
ISSN 1879-1026
Publication date 2016-12-15
Year available 2017
Sub-type Article (original research)
DOI 10.1016/j.scitotenv.2016.11.181
Open Access Status Not yet assessed
Volume 580
Start page 367
End page 379
Total pages 13
Place of publication Amsterdam, Netherlands
Publisher Elsevier BV
Language eng
Subject 2305 Environmental Engineering
2304 Environmental Chemistry
2311 Waste Management and Disposal
2310 Pollution
Abstract Assessing recharge is critical to understanding groundwater and preventing pollution. Here, we investigate recharge in an Australian coastal aquifer using a combination of physical, modelling and geochemical techniques. We assess whether recharge may occur through a pervasive layer of floodplain muds that was initially hypothesized to be impermeable. At least 59% of the precipitation volume could be accounted for in the shallow aquifer using the water table fluctuation method during four significant recharge events. Precipitation events <. 20. mm did not produce detectable aquifer recharge. The highest recharge rates were estimated in the area underneath the floodplain clay layer rather than in the sandy area. A steady-state chloride method implied recharge rates of at least 200. mm/year (>. 14% of annual precipitation). Tritium dating revealed long term net vertical recharge rates ranging from 27 to 114. mm/year (average 58. mm/year) which were interpreted as minimum net long term recharge. Borehole experiments revealed more permeable conditions and heterogeneous infiltration rates when the floodplain soils were dry. Wet conditions apparently expand floodplain clays, closing macropores and cracks that act as conduits for groundwater recharge. Modelled groundwater flow paths were consistent with tritium dating and provided independent evidence that the clay layer does not prevent local recharge. Overall, all lines of evidence demonstrated that the coastal floodplain muds do not prevent the infiltration of rainwater into the underlying sand aquifer, and that local recharge across the muds was widespread. Therefore, assuming fine-grained floodplain soils prevent recharge and protect underlying aquifers from pollution may not be reasonable.
Keyword Aquifer
Q-Index Code C1
Q-Index Status Provisional Code
Grant ID LP130100498
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Civil Engineering Publications
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