Tracking groundwater nutrients using novel tracers to inform coastal watershed management in South Kohala, Hawaiʻi
We propose to provide land use managers in the South Kohala Coastal Partnership information that identifies the path of the groundwater that emerges at the coast, and estimates of fractions of nutrients and microcontaminants originating from different land-use categories in the watershed. This information will enable managers to better prioritize areas for nutrient and wastewater management that could improve coral reef health and resilience. We will identify most probable groundwater flow lines emerging at the Kohala coastline from the watershed. Groundwater flow lines will then help identify land-use categories that are potential nutrient and contaminant contributors to groundwater. Further, we will establish a chemical connection between land-use categories and the coastline using source specific microcontaminants (targeting OSDS, WWTP, golf courses and resort landscaping) and confirm linkage between individual land-use categories and nutrients in SGD. We will utilize the combination of δ15N of nitrate and microcontaminants (pharmaceuticals and pesticides) as source tracers.