Abstract
A lack of closely spaced datasets on layer elevations, aquifer parameters, identification of areas with high recharge potential, dominant conduit porosity zones, and well defined boundary conditions hampers the ability of groundwater models to produce a reliable water balance. Typically, geological structure, aquifer properties, and groundwater heads are obtained from point measurements which are sparse. The drillhole information in aquifers is usually available at locations far apart, distances ranging from hundreds to thousands of meters. Furthermore, pump tests are usually conducted at limited locations and generalized to the aquifer. This limited knowledge leads to errors in the conceptual understanding of the aquifer. In this study, Airborne Electromagnetic Survey (AEM) was used to define base elevations of the aquifers where drillhole information was lacking. Surface Nuclear Magnetic Resonance (sNMR), borehole NMR, Transient Electromagnetic (TEM), and downhole geophysical surveys have given new insight to the conceptualization of hydrogeological framework. These methods are relatively low in cost compared to traditional well drilling and provide information on layer elevations, aquifer parameters, point and diffuse recharge zones, and conduit porosity zones in the profile, which improves our definition of the boundary conditions. From a practical point of view, combining drillhole information with a variety of geophysical techniques provides sound datasets to develop a comprehensive conceptual model. This in turn can be used to build a robust groundwater model.
Highlights
For effective groundwater management, reliable estimation of the water balance is a pre-requisite.Groundwater models are commonly developed to understand regional groundwater systems and guide the decisions on water resources management [1]
We provide results for Surface Nuclear Magnetic Resonance (sNMR) site 6 where a 250 mm diameter production well (ULE216) and a monitoring well (ULE215) were drilled for testing sNMR
The use of sNMR, bNMR, Transient Electromagnetic (TEM), and downhole geophysical surveys have given new insight to conceptualization of hydrogeological framework of the Uley South Basin. These methods are relatively the conceptualization of hydrogeological framework of the Uley South Basin. These methods are low cost compared to traditional well drilling; and sNMR and TEM can be applied at sites inaccessible relatively low cost compared to traditional well drilling; and sNMR and TEM can be applied at sites for drilling
Summary
Reliable estimation of the water balance is a pre-requisite.Groundwater models are commonly developed to understand regional groundwater systems and guide the decisions on water resources management [1]. Groundwater models provide a scientific and predictive tool for determining appropriate solutions to water allocation, surface water–groundwater interaction, landscape management, or impact of new development scenarios. If modelling studies are not well designed from the outset, or the model doesn’t adequately represent the natural system being modelled, the modelling effort may be largely wasted, or decisions may be based on flawed model results, and long term adverse consequences may result [2]. In this context, it is considered that uncertainty in model results arise from errors in model structure, inputs, and parameters [3]. Rojas et al [3] discussed this aspect further illustrating the fact that, typically, the geological structure is only partially known and point measurements of subsurface properties
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