Simplified approach in karst aquifer characterization by using discharge variability, storage capacity, and void development: A preliminary study in the tropical karst region

One of the main challenges in karst water management is the limited availability of measured hydrogeological data. This research aimed to employ a simplified approach for aquifer characterization by applying discharge variability, storage capacity, and void development (Dk), where the only required data is the spring discharge. The approach was applied in two distinct tropical karst aquifers: Gunungsewu (older karst dominated by sub-surface flow) and Rengel (younger karst with fluvial domination). Master recession curve (MRC) and autocorrelation were used to evaluate Dk and storage capacity, while the flow duration curve (FDC) and spring coefficient of variation parameter (SCVP) were applied to ascertain discharge variability. The result was able to differentiate the karst systems into three types, termed (G1) low discharge variability and storage capacity (G2) moderate discharge variability and high storage capacity, and (G3) low discharge variability and high storage capacity, also considered to be the most efficient aquifer for water supply. Spatially, wide variation occurred in karst systems dominated by sub-surface flow because of material thickness, fissure void formation, and swallow hole recharges. On the other hand, karst with fluvial domination belonged to the G2 type due to the persistent recharge from surface rivers. Furthermore, this study hypothesizes that the developed karst structure with a large catchment area possibly possesses G3 aquifer type stemming from extensive diffuse void (epikarst zone) continuously recharging the spring. © 2023 The Author(s)