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Accueil du site → Doctorat → Australie → The hydrogeochemistry of shallow groundwater in Western Sydney : a study of salinisation processes in shallow groundwater

University of Sydney (2016)

The hydrogeochemistry of shallow groundwater in Western Sydney : a study of salinisation processes in shallow groundwater

Taylor, Sarah Leanne

Titre : The hydrogeochemistry of shallow groundwater in Western Sydney : a study of salinisation processes in shallow groundwater

Auteur : Taylor, Sarah Leanne

Université de soutenance : University of Sydney

Grade : Doctor of Philosophy (PhD) 2016

Résumé
Groundwater salinity is widespread in Western Sydney ; however, little is known about the processes which cause it. This thesis explored many features of the shallow groundwater system using a range of hydrogeological, geochemical and statistical techniques. Geostatistical analysis of historical data highlighted that 53.6% of the study region had shallow groundwater with an electrical conductivity exceeding 2,000µS/cm. Salinisation hazard mapping indicated that 0.66% of the region has a high salinisation hazard and 54.2% has a moderate salinisation hazard. The high-temporal-resolution dataset collected for this study, allowed the recharge and salt source (modern rainfall) to be identified, plus mechanisms of salt accumulation (cyclic process of evaporation and re-dissolution driven by high rates of evapotranspiration and clay-rich soils), and transport. From this, a geochemical model identifying the processes contributing to groundwater salinisation, and a conceptual model of the hydrogeological system were developed. Multivariate analysis identified seven water-types, their geographical distribution, and the causes of temporal variability for each water-type. Saline groundwater was found in many parts of the landscape, though temporal variability was generally limited. The monthly comparison approach, which analyses temporal variability, was developed for this study. This method increased our understanding of system variability and its causes, ultimately improving the conceptual model. The conceptual model generalises the geographical distribution of water-types based on landscape features, while temporal variability is related to water-types. The model significantly improves our understanding of the groundwater system, and our ability to manage it. Additionally, this study has illustrated that groundwater salinity arising from evaporative processes could be more wide-spread than currently thought, and may not be confined to arid or semi-arid environments.

Mots clés : hydrochemistry groundwater salinity Western Sydney

Présentation

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Page publiée le 11 juillet 2017