Identification of Karstification Zoning and Aquifer Channels in Karst Basin at Sendang Biru Beach, Malang-Indonesia: A Case Study

Karst zoning and channel aquifers in the karst basin at Sendang Biru Beach, Tambak Rejo Village have been investigated. Sendang Biru Beach has a cave appearance as a karst morphological feature and is composed of limestone. Seasonal karst water sources come from springs, surface runoff, underground rivers, channels in valleys, basins, and slopes that often experience drought. The purpose of this study is to identify the presence of karst aquifers and karstification zones that are prone to damage or disasters in the karst environment. The method used is a geophysical combination of Electrical Resistivity Tomography (ERT), Induced Polarization (IP), and Self Potential (SP). The results showed that the eastern part's karstification zone was characterized by moderate to high resistivity and a chargeability zone with a moderate to high range. In addition, the existence of karst aquifer channels in the anomalous zone of low resistivity, high chargeability, and negative natural potential. This zone is located in the Qas Formation, with the water flowing from west to east and from west to south. The inundated karst aquifer that spreads in a circular pattern with different depths interspersed by limestone cracks causes a heterogeneous karstification process.