Geological controls and tidal forcing of submarine groundwater discharge from a confined aquifer, Elim Beach, northeast Australia

Stieglitz, T.C., Holliday, D., Ridd, P.V., Cook, P.G., and Read, W.W. (2010) Geological controls and tidal forcing of submarine groundwater discharge from a confined aquifer, Elim Beach, northeast Australia. In: Abstracts from ASLO & NABS 2010 Summer Meeting, p. 1. From: ASLO & NABS: 2010 Summer Meeting, 6 - 11 June 2010, Santa Fe, NM, USA.

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Abstract

Discharge of fresh groundwater from large, discrete springs in the intertidal zone is documented at a remote beach in North East Australia. The geologic and hydraulic controls of this spring discharge were investigated, using a combination of geological, geophysical and hydrological tools. A sharp subsurface gradient of electrical ground conductivity as well as state recovered from sediment cores indicate the presence of a sandy clay layer providing aquifer confinement ca. 1m below the seafloor. Spring discharge occurs where this layer is breached. Net hydraulic head and groundwater discharge flux were inversely correlated with tidal water level, but remained positive throughout he tidal cycle. An increase in hydraulic head with increasing tidal water level was observed, which can be explained by a change in hydraulic pressure of the confined aquifer in response to a differential pressure forcing a t the seaward limit of the confining aquifer in response to a differe3ntial pressure forcing at the seaward limit of the confining sedimentary until. Long-term time series of discharge volume recoded with purpose-built seepage meters indicate no diet response to rainfall, and rather suggest a substantial lag between recharge and discharge, which is also confirmed by CFC groundwater ages of tens of years. The continuous presence of fresh groundwater in the intertidal zone affects the near shore vegetation-Melaleuca trees which are usually associated with freshwater swamps are here growing in the intertidal zone, with root inundation occurring at every high tide.

Item ID: 16167
Item Type: Conference Item (Abstract / Summary)
Date Deposited: 05 May 2011 01:28
FoR Codes: 04 EARTH SCIENCES > 0405 Oceanography > 040503 Physical Oceanography @ 100%
SEO Codes: 96 ENVIRONMENT > 9611 Physical and Chemical Conditions of Water > 961102 Physical and Chemical Conditions of Water in Coastal and Estuarine Environments @ 100%
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