Spatially dense drip hydrological monitoring and infiltration behaviour at the Wellington Caves, South East Australia

Abstract

Despite the fact that karst regions are recognised as significant groundwater resources, the nature of groundwater flow paths in the unsaturated zone of such fractured rock is at present poorly understood. Many traditional methods for constraining groundwater flow regimes in karst aquifers are focussed on the faster drainage components and are unable to inform on the smaller fracture or matrix-flow components of the system. Caves however, offer a natural inception point to observe both the long term storage and the preferential movement of water through the unsaturated zone of such fractured carbonate rock by monitoring of drip rates of stalactites, soda straws and seepage from fractures/micro fissures that emerge in the cave ceiling. Here we present the largest spatial survey of automated cave drip rate monitoring published to date with the aim of better understanding both karst drip water hydrogeology and the relationship between drip hydrology and surface climate. By the application of cross correlation functions and multi-dimensional scaling, clustered by k-means technique, we demonstrate the nature of the relationships between drip behaviour and initial surface infiltration and similarity amongst the drip rate time series themselves that may be interpreted in terms of flow regimes and cave chamber morphology and lithology.