1. Assessing Drivers, Scales, and Impacts of Coastal Groundwater Discharge on Hawai’i Peter W. Swarzenski USGS-Santa Cruz, CA Hawaii Coastal Water Quality Meeting University of Hawai’i, Hilo, Hawai’i MARCH 21, 2011

2. - Coastal groundwater discharge (how much and where) - Associated constituent loadings (mar vs terr vs atmos) - Sea-level rise impacts (’drowning’ of coastal ecosystems) - Buffering capacity (pH, temp, salinity contours) - Coastal water budgets (residence times, salinity) - C, Si, N, P cycling (as macro nutrients) - Impacts on seagrass health (S - poisoning, temperature) - Impacts of foraging fish (salinity, food, water quality) USGS coastal groundwater project goals Land-based Resistivity Image

3. Radon- 222 Rn Short half-life (3.8 d) gw: high sw: low Model for gw discharge Low tide coincident Rn peaks Geochemical tracers

4. Low tide High tide Land-based resistivity to examine tidal modulation of the fresh water /saltwater interface: KIHOLO BAY, Hawai’i zones of enhanced flow Geophysical techniques N. Dimova Shore parallel

5. Why do this work?? Quantify amount of groundwater coming to the nearshore Quantify gw-derived constituent loadings Assess terrestrial vs marine drivers Assess related ecosystem vulnerability/services