Author: Jyoti Maggu
Maggu, Jyoti, 2024 Hydrochemical Characteristics and Groundwater Evolution of a Cambrian Limestone Aquifer, the Northern Territory, Flinders University, College of Science and Engineering
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The Cambrian Limestone Aquifer (CLA) in the Northern Territory, occupying parts of the Daly and Wiso geological basins is the focus of this study, due to its importance as a water resource, in the semi-arid region of the basins. The Beetaloo sub-basin, located within these basins, has been earmarked for the development of onshore gas due to the vast reserves of gas that it holds. The threats posed from the future development of the gas industry has raised concerns regarding the future of the CLA. This study seeks to provide baseline information on hydrogeological and geochemical processes that influence the water quality of the CLA, which may be used in the future for the management of this valuable resource. The study involves the determination of major regional flow paths and analysis of a large water chemistry dataset (including pH, total dissolved solids and 9 major elements) to better understand the chemical composition of groundwater and to infer the major geochemical processes responsible for variations in water chemistry along regional flow paths. This water quality dataset, compiled from a range of government and industry sources, was used to study the variations in the water chemistry or dominant major ions using a range of commonly employed techniques in hydrochemical studies: correlation matrices, piper diagrams, ionic plots and geochemical modelling. The assessment identifies that regional chemical variations are complex and are a function of several controlling processes, including climatic conditions, recharge locations, groundwater residence times, mixing processes and various water-mineral interactions, with minimal evapotranspiration (ET) effects. Geochemically, the primary control on groundwater chemistry of the CLA is dominated by carbonate reactions owing to its dominant calcite/dolomite mineralogy. Additional processes, such as silicate hydrolysis, cross- formational flows, pyrite oxidation and cation exchange processes are considered important at local scales. This study serves an important basis for understanding the complexity of chemical reactions in the CLA and can be applied to the broader CLA to better inform future management of this valuable resource.
Keywords: Cambrian Limestone Aquifer, Beetaloo sub-basin, Groundwater, Water Quality, Water Chemistry, Major Ions, Geochemical processes, Flow paths, Hydrochemical, Correlation matrix, Piper diagram, Ionic plot, Geochemical modelling, Water-mineral interaction
Subject: Earth Sciences thesis
Thesis type: Masters
Completed: 2024
School: College of Science and Engineering
Supervisor: Dr Dylan Irvine