Factors Affecting Hydrochemistry of Karst Springs and their Relationship to Aquifer Development

This study aims to determine the differences in hydrochemistry, the factors influencing these differences, and their relationship with karst aquifer development in Jonggrangan Karst, Java Island, Indonesia. The discharges were measured in three springs and the slow-flow percentage was separated. Furthermore, Principal Component Analysis (PCA) was conducted to determine the factors affecting hydrochemical conditions, while the karst aquifer development level was analyzed using the Master Recession Curve (MRC) method. The three springs showed variations in hydrochemistry due to different discharge fluctuations controlled by the karst aquifer nature in releasing its groundwater storage. Anjani Spring showed most fluctuations, while Kiskendo and Mudal Springs were relatively stable. The results also revealed that the hydrochemical conditions were influenced by the same main principal factors. When slow-flow is dominant during the dry season, carbonate mineral dissolution-precipitation is the primary process, whereas when quick-flow is dominant during flood events, dilution by precipitation causes carbonate mineral dissolution. Meanwhile, mixing with rainwater, water infiltration from the unsaturated zone, and interaction with clastic rock were secondary principal factors. Based on MRC analysis, the Anjani Spring had the most developed aquifer with a value of 8, while the Kiskendo and Mudal Springs had a value of 5.5. The higher value of karst aquifer development at the Anjani Springs led to the development of more diverse and large voids (conduits), which allowed water to be transported with more variable velocity and residence time. Therefore, the hydrochemical conditions of this spring fluctuated the most compared to the other springs. © 2021, The Author(s), under exclusive licence to Springer Nature Switzerland AG.