Abstract
Abstract. Cave drip water response to surface meteorological conditions is complex due to the heterogeneity of water movement in the karst unsaturated zone. Previous studies have focused on the monitoring of fractured rock limestones that have little or no primary porosity. In this study, we aim to further understand infiltration water hydrology in the Tamala Limestone of SW Australia, which is Quaternary aeolianite with primary porosity. We build on our previous studies of the Golgotha Cave system and utilize the existing spatial survey of 29 automated cave drip loggers and a lidar-based flow classification scheme, conducted in the two main chambers of this cave. We find that a daily sampling frequency at our cave site optimizes the capture of drip variability with the least possible sampling artifacts. With the optimum sampling frequency, most of the drip sites show persistent autocorrelation for at least a month, typically much longer, indicating ample storage of water feeding all stalactites investigated. Drip discharge histograms are highly variable, showing sometimes multimodal distributions. Histogram skewness is shown to relate to the wetter-than-average 2013 hydrological year and modality is affected by seasonality. The hydrological classification scheme with respect to mean discharge and the flow variation can distinguish between groundwater flow types in limestones with primary porosity, and the technique could be used to characterize different karst flow paths when high-frequency automated drip logger data are available. We observe little difference in the coefficient of variation (COV) between flow classification types, probably reflecting the ample storage due to the dominance of primary porosity at this cave site. Moreover, we do not find any relationship between drip variability and discharge within similar flow type. Finally, a combination of multidimensional scaling (MDS) and clustering by k means is used to classify similar drip types based on time series analysis. This clustering reveals four unique drip regimes which agree with previous flow type classification for this site. It highlights a spatial homogeneity in drip types in one cave chamber, and spatial heterogeneity in the other, which is in agreement with our understanding of cave chamber morphology and lithology.
Highlights
Karst features in limestone are typically developed from the solutional dissolution of fractures and bedding planes in carbonate rocks (Arbel et al, 2010; Kurtzman et al, 2009)
Based on the findings of these two studies, here we investigate the relationship between drip water hydrology and cave depth, spatial location, and stalactite type, and develop a hydrological classification scheme that is appropriate to high-frequency drip logger data and limestones with a primary porosity
This study explores the relationship between drip water and rainfall in a SW Australian karst, where both intra- and interannual hydrological variations are strongly controlled by seasonal variations in recharge
Summary
Karst features in limestone are typically developed from the solutional dissolution of fractures and bedding planes in carbonate rocks (Arbel et al, 2010; Kurtzman et al, 2009). Complex spatial spreading of various karst features such as solutionally widened fractures, caves, and conduits makes the monitoring and precise groundwater recharge modeling very difficult (Lange et al, 2003; Arbel et al, 2010). The upper part of karstified rock (the epikarst zone) has higher permeability than the underlying vadose zone (Klimchouk, 2004).
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