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 Research Projects 2020-2022

Collaborative study of groundwater transport paths and discharge loads of wastewaters and other land-uses that impact the Ewa coastal zones of West Oʻahu

Co-INVESTIGATORS: Aly El-Kadi, Celia Smith, Marek Kirs, Niels Grobbe, Robert Whittier
Graduate Fellows: John Cameron, Matthew Duff

Map view of coastline with super-composed thermal data showing locations of groundwater entry of ocean
Submarine groundwater discharge can be mapped at low-cost and high-resolution using remote controlled UAVs (drones) outfitted with aerial Thermal Infrared sensors, as illustrated in this image. Blue tones stand out, showing where cold groundwaters enter warmer coastal ocean waters (reds).

The risk that sewage effluent released to the environment poses to human health and the environment is well documented, and human-health risks and environmental impacts of terrestrial wastewater disposal are of global concern. The ecological impacts of anthropogenic loading are becoming increasingly clear. High system density or improper function can lead to contamination of aquifers and adjacent surface waters by nutrients, pathogens and pharmaceuticals. Thus, on-site sewage disposal systems (OSDS) are a substantial threat to groundwater quality and the second-most frequently reported cause of contaminated groundwater. Developing a complete understanding of the environmental and health risks of wastewater leakage from OSDS thus remains a fundamental and critical concern for the state of Hawaiʻi. Our goal is to assess the hydraulic and geochemical connectivity between OSDS wastewater and other land use and the oceanic waters of areas around the greater Ewa Beach area on the southwest coast of Oahu. To achieve this goal, our objective is to investigate the flow paths of contaminant transport from known occurrences of OSDS by integrating remote sensing and field studies of submarine and subterranean groundwater and shoreline nutrient loads and N-stable isotope of waters and algae and microbial fingerprinting into advanced watershed and groundwater dissolved solute transport models. New results of research and the wealth of data generated will advance the state of science and provide solutions for water pressing problems. Most importantly, we feel, is that the state of Hawaiʻi will greatly benefit from the hydrologic research for deigning remediation strategy of a critically important OSDS problem.