Automated image analysis for experimental investigations of salt water intrusion in coastal aquifers

A novel methodology has been developed to quantify important salt water intrusion parameters in a sandbox experiment using image analysis. Existing methods found in the literature are based mainly on visual observations, which are subjective, labour intensive and limit the temporal and spatial resolutions that can be analysed. A robust error analysis was undertaken to determine the optimum methodology to convert image light intensity to concentration. Results showed that defining a relationship on a pixel-wise basis provided the most accurate image to concentration conversion and allowed quantification of the width of the mixing zone between salt water and freshwater. A high image sample rate was used to investigate the transient dynamics of salt water intrusion, which rendered analysis by visual observation unsuitable. This paper presents the methodologies developed to minimise human input, promote autonomy, provide high resolution image to concentration conversion, and allow the quantification of intrusion parameters under transient conditions.