Oral presentation: Titus Kruijssen

Quantifying groundwater recharge and lateral transport is essential to monitor freshwater storage, and to assess nutrient and other contaminant fluxes toward groundwater-dependent ecosystems, including the coral reefs surrounding Curaçao. However, the island’s fractured rock geology hosts a highly heterogeneous groundwater system, complicating monitoring and hydrogeological conceptualization.

We applied a multi-parameter approach to characterize recharge and lateral groundwater discharge in the island’s subsurface by integrating time series of groundwater tables, electrical conductivity (EC) and temperature, with depth profiles of groundwater EC and temperature. This multi-parameter analysis revealed rapid groundwater table rises and coincident changes in groundwater quality directly after intense rainfall events, indicating rapid groundwater recharge through fracture zones in the shallow subsurface.

The multi-parameter dataset further reveals peaks in groundwater drainage through shallow ephemeral streambed aquifers (rooien), indicating prolonged groundwater throughflow at the coastline. Furthermore, stepwise changes in groundwater EC and temperature with depth suggest focused lateral groundwater transport through deeper fracture zones, supported by heat tracer experiments and borehole video observations.

Together, the results inform an updated conceptual hydrogeological model of the island. The pronounced spatiotemporal focusing of groundwater recharge and transport implies short-lived but intense pulses of nutrient and other contaminants towards Curaçao’s fringing reefs. This emphasizes the importance for high-resolution groundwater table, EC and temperature monitoring to support effective management of pollution sources in recharge areas and ephemeral stream systems. This study is funded by the Dutch national science foundation (NWO), part of SEALINK research project.