Browsing by Author "Cheng, X"

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    Analysis of environmental isotopes in groundwater to understand the physical and chemical responses of a coastal aquifer to pumping.
    (International Association of Hydrogeologists, 2013-09-20) Currell, MJ; Cendón, DI; Cheng, X
    The response of a multi-layered coastal aquifer in southeast Australia to decades of groundwater pumping, and the groundwater age, flow paths and salinisation processes were examined using isotopic tracer (δ18O, δ2H , δ13C, 3H and 14C). Groundwater radiocarbon (0.91 To 77.8 pMC) and tritium (below detection to O.23TU) contents decline with distance and depth away from basin margins; however, in the main zone of pumping, radiocarbon activities are generally homogeneous within a given depth horizon. A lack of tritium and low radiocarbon activities (<25 pMC) in groundwater in and around the pumping areas indicate that seasonal recovery of water levels (observed each year since c.1970) is related to capture of water with low tracer activities, rather than arrival of water recharged in modern times. Possible sources of water facilitating the seasonal recovery include release from storage in low permeability layers and/or horizontal transfer of water from more distant, undeveloped parts of the basin. Groundwater δ18O, δ2H and chloride contents indicate mixing between fresh meteoric water that is slightly depleted in stable isotopes relative to the local weighted mean, and marine water. On the basis of mixing calculations performed with Cl and δ18O, the most saline groundwater approximates an 80:20 mixture of fresh to oceanic water. Leakage of marine water into the Westernport Group sediments through an incised tidal channel, and dilution of this water by fresh groundwater released from other sources (e.g. aquitards or offshore sediments) can explain the observed Cl-δ180 values. Overall stability in seasonally recovered water levels and groundwater salinities over the past 3 decades indicate that the system has likely reached a state of dynamic equilibrium with respect to water balance and solute compositions, following a major change in the ow system and solute distributions that occurred in the early stages following development of the aquifer. Complex geological structure and variable degrees of flushing of saline water (largely controlled by proximity to recharge sources), result in heterogeneous groundwater salinities around the coastline.
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    Analysis of environmental isotopes in groundwater to understand the response of vulnerable coastal aquifer to pumping: Western Port Basin, south-eastern Australia
    (Springer, 2013-11-01) Currell, MJ; Cendón, DI; Cheng, X
    The response of a multi-layered coastal aquifer in southeast Australia to decades of groundwater pumping, and the groundwater age, flow paths and salinization processes were examined using isotopic tracers. Groundwater radiocarbon and tritium contents decline with distance and depth away from basin margins; however, in the main zone of pumping, radiocarbon activities are generally homogeneous within a given depth horizon. A lack of tritium and low radiocarbon activities (< 25 pMC) in groundwater in and around the pumping areas indicate that seasonal recovery of water levels is related to capture of old water with low radioisotope activities, rather than arrival of recently recharged water. Mechanisms facilitating seasonal recovery include release of water from low-permeability layers and horizontal transfer of water from undeveloped parts of the basin. Overall stability in seasonally recovered water levels and salinities for the past three decades indicate that the system has reached a dynamic equilibrium with respect to water balance and salinity, following a major change in flow paths and solute distributions after initial development. Groundwater delta O-18, delta H-2 and chloride contents indicate mixing between fresh meteoric-derived groundwater and marine water at the coast, with the most saline groundwater approximating an 80:20 mixture of fresh to oceanic water. © 2013, Springer.
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    Erratum: Analysis of environmental isotopes in groundwater to understand the response of a vulnerable coastal aquifer to pumping: Western Port Basin, south-eastern Australia
    (Springer Nature, 2013-09-19) Currell, MJ; Cendón, DI; Cheng, X
    A monitoring well, bore ID 71856, is indicated as being screened in the Sherwood formation in Tables 1 and 2; in fact it is screened within the Older Volcanics unit. This error was noticed after the proofs were approved for publication. © 2013, Springer.