HR: 16:15h
AN: H24A-02    [Abstracts]
TI: Utilising Physical, Chemical, And Stable Isotope Techniques To Delineate The Flows Within A Coastal Wetlands System
AU: Marimuthu, S
EM: marimuth@cwr.uwa.edu.au
AF: Centre For Water Research, The University Of Western Australia, 35 Stirling Highway, Crawley, Perth, WA 6009 Australia
AU: * Reynolds, D A
EM: reynolds@cwr.uwa.edu.au
AF: Centre For Water Research, The University Of Western Australia, 35 Stirling Highway, Crawley, Perth, WA 6009 Australia
AB: The coastal wetlands system under study comprises a series of small lakes and is very unique in the sense that the lakes within the system display different hydrochemistry and stable isotopic composition although they are connected by channels and form as a cluster of inter-connected lakes. The complex flow systems and the transient nature of the interactions between surface water and groundwater present in the wetlands system were delineated using both chemical and stable isotope data to supplement existing classical hydraulic data. The spatial and temporal variations of chemical and isotopic composition of the individual water bodies within the system were measured for an annual cycle, to provide a unique data set for the analysis. A purely hydraulic analysis of the region surrounding the wetlands would indicate that the wetlands are flow-through bodies, however the chemical and isotope information indicates the lakes almost invariably act as discharge points for the surface water flows and the north south regional groundwater flow. Large volumes of groundwater flow were found within an observed northeast-southwest trending paleochannel within the wetlands system, and in this case, the chemical and isotopic evidence are complimentary with the hydraulic study. The isotope and chloride results from the surface water bodies allowed for the accurate determination of the composition of the major creeks in the system, and a simple portioning model indicated that groundwater is the predominant source for the inflowing creeks. Similarly, the deuterium versus Oxygen-18 and deuterium versus chloride relationships observed in the system portray two distinct evaporation trends, one through the hypersaline lakes and the other through less saline lakes which indicates that the isotopic composition of the water bodies are affected to a great extent by high dissolved salts content. The superposition of these data sets provided a unique vision of the flow system and clearly shows that certain lakes are significantly different from a compositional standpoint to other lakes although a bathymetric survey conducted on the wetlands system indicated otherwise.
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
DE: 1860 Runoff and streamflow
DE: 1871 Surface water quality
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting