COCKPIT-PLUS: A proposed method for rapid groundwater vulnerability-driven land use zoning in tropical cockpit karst areas

Karst groundwater is highly vulnerable to contamination, which urges better land use zoning. This paper proposes a new approach, called COCKPIT-PLUS, to minimize groundwater contamination within cockpit karst regions. The method employed four parameters: P (the existence of ponor/swallow hole), L (lineament density), U (sinking stream to an underground river), and S (distance to spring/pumping site). These parameters are essential for identifying contaminant pathways and transport from the surface to the karst groundwater/springs. COCKPIT-PLUS has been developed and validated in the Gunungsewu karst in Java, Indonesia. This research considers a cockpit as a single hydrological unit that uniquely recharges karst groundwater. We analyzed 2,811 cockpits and 81 other closed depressions to develop a land use planning map. The research used the time to first arrival (Ta), time to peak (Tp), and Q_max/min ratio parameters of two karst springs and two underground pumping sites for validation. Cockpits with ponors/swallow holes, sinking streams, high lineament density, and short distances to springs are vulnerable to groundwater and thus must be restricted areas for any land uses. The findings show that though the COCKPIT-PLUS uses a limited karst dataset, the proposed method seems reliable enough for a rapid land-use zoning approach in cockpit karst areas.