Towards a Numerical Approach to Identify Hydrogeological Landscape Units

Abstract:

Groundwater salinity remains a major issue due to its impact on agriculture and infrastructure. In Australia, it is recognized that groundwater salinity varies significantly across space and time. In NSW, the state government has developed a landscape classification for management based on hydrogeology, landuse and landscape aspects, mainly derived from GIS overlays and operator experience. In this study, we use historical water quality data, geology and drilling logs to develop a more rigorous numerical approach to landscape classification. A combination of statistical methods (Generalised additive model (GAM) and Semi-variogram analysis) was used to identify the significant spatio-temporal factors that induce the variability of groundwater salinity across the Muttama catchment (1059km²) in the southern part of NSW, Australia.

The statistical model explained 57% of the variance in the electrical conductivity levels in the groundwater across the landscape. Geology and lag rainfall were the key factors that explained overall catchment groundwater salinity, thus defining the hydrogeological landscape units. Semi-variogram analysis revealed the remaining residuals did not indicate further spatial organisation. Current work focusses on also predicting groundwater response times.

Therefore, the results of this study highlighted framework to numerically develop hydrogeological units based on the geological landscape characteristics.