Hydrogeological Drivers and Fate of Spring Discharge in a Semi-arid and Remote Setting

Résumé du livre

Globally, springs are a critical source of water to wetland ecosystems and often hold high ecological and cultural significance (Bogan et al., 2014; Silcock et al., 2020). Springs often occur due to geological features (such as faults) that provide a pathway or barrier to groundwater flow, leading to discharge to the surface. There is a need for further research of these systems including the relationships between aquifer hydraulic head and spring discharge, and the regional hydraulic and hydrochemical flow systems. -- This thesis addresses these limitations through the presentation of a detailed literature review, and three research chapters on a hydrogeological system that includes faults and springs. The research chapters utilise the Doongmabulla Springs Complex (DSC) and surrounding area in Queensland, Australia as a case study. The DSC are an important system to study given the high ecological and cultural values and the potential for impacts from a nearby mining development. -- The outcomes of this thesis help to improve the understanding of fault-controlled spring systems through a global review and three research chapters examining the DSC and the surrounding region. The three research chapters helped in reducing the uncertainty in the conceptualisation of the DSC and the surrounding hydrogeological system. Chapter 3 found that the Triassic aquifers were more likely than the Permian aquifers to have adequate hydraulic head to support spring flow from the DSC. Similarly, Chapter 4 showed likely discharge features in the hydraulic head surface of the Triassic aquifers near the several rivers, lakes and the DSC. Chapter 5 found differing salinities within the separate units of the Triassic aquifers suggesting that the springs may receive a mixture of water from local and more regional scale flow paths. These observations have important implications for the DSC, as changes to groundwater flow paths due to mine-induced drawdown may impact the contribution of the local and regional flow paths, potentially reducing the rate of spring discharge and impacting the water quality. Given the sensitivities of spring-dependent ecosystems to changes in flow and salinity, further investigation is merited.