Electromagnetic Imaging of Prior Stream Channels using a DUALEM-421 and Inversion

摘要

Prior stream channels occupy 15% of the clay alluvial fields used for irrigated cotton production in the lower Gwydir Valley in north-western NSW. They act as significant hydrological features offering pathways for deep draining water to interact withburied palaeochannels. We need to map the connectivity and spatial extent of these formations to improve the scientific understanding of the associated hydrological processes in this region. In this paper we explore this by first measuring the apparentelectrical conductivity (oa) of the soil with a DUALEM-421. Subsequently, we employ 1-dimensional (1-D) inversion algorithms with 2-dimensional (2-D) smoothness constraints to predict the true electrical conductivity (a) using DUALEM-2d (partial solution) and DUALEM-2d-Full (full solution). The o models obtained are compared with soil data (including particle size fractions, soil texture, EC_(1:5) and CEC) collected across the field. All a models generally reflect the soil properties which characterisethe physiographic units of a prior stream channel and the clay alluvial plain. However, the relationship between the measured soil properties and estimated delta is weak and further research is needed to achieve better relationships.