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Quantifying Groundwater Discharge from the Faga’alu Aquifer, American Samoa


PRINCIPAL INVESTIGATOR:

Dr. Henrietta Dulai, Assistant Professor, Geology and Geophysics

SPONSOR:

National Institute for Water Resources, Water Resources Research Institute Program

PROJECT PERIOD:

03/01/2014-02/28/2015

ABSTRACT:

Faga’alu Valley on Tutuila Island, American Samoa, has been designated as a priority watershed management area by the NOAA Coral Reef Conservation Program. While Faga’alu’s surface water is on the AS EPA 3 03(d) list of impaired waters (CRCP 2013), at present, there is no information available regarding groundwater derived pollution in the valley. In its coral rich bay, near-shore ecosystem health is threatened by terrigenous sediments, nutrients, and other pollutants that are likely transported via stream and groundwater discharge (CWP 2012). The American Samoa Environmental Protection Agency’s (ASEPA) coral reef monitoring program has determined that Faga’alu’s benthic ecosystem is one of the most impacted on the island (Houk 2005).

This study strives to evaluate surface-water-groundwater interactions within Faga’alu Stream and to quantify groundwater to stream flux and submarine groundwater discharge rates into Faga’alu Bay. Since groundwater has been shown to be a potentially significant source of nutrients and other anthropogenic contaminants in similar environments (Johannes and Hearn 1985, Dulaiova et al. 2006, Burnett et al. 2007) a more complete understanding of groundwater derived contributions are needed to assess the degree of anthropogenic impact and nutrient loading to the coastal ecosystem. By examining multiple geochemical parameters and integrating ground/stream water flux rates with nutrient and isotopic tracer data we are currently working to quantify contaminant loading from different sources, and assess the degree of human impact on this fragile ecosystem.

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