| Institution: | 1. Waterways Centre for Freshwater Management, School of Earth and Environment, University of Canterbury, Christchurch, Canterbury, New Zealand;2. National Marine Science Centre, Southern Cross University, Lismore, New South Wales, Australia
Department of Marine Sciences, University of Gothenburg, Gothenburg, Sweden;3. SCU Geoscience, Southern Cross University, Lismore, New South Wales, Australia;4. Centre for Atmospheric Research, School of Earth and Environment, University of Canterbury, Christchurch, Canterbury, New Zealand;5. Independent, Lawrenceville, New Jersey, USA |
| Abstract: | Coastal lagoons are significant wetland environments found on coastlines throughout the world. Groundwater seepage may be a key component of lagoon water balances, though only a few studies have investigated large (>100 km2) coastal lagoons. In this study, we combined airborne thermal infrared imagery with continuous measurements of radon (222Rn—a natural groundwater tracer), conductivity, water temperature and dissolved oxygen to map groundwater seepage to a large coastal lagoon in New Zealand. We found evidence of seepage along the margins of the lagoon but not away from the margins. Our findings confirmed previously known seepage zones and identified new potential locations of groundwater inflow. Both point source and diffuse seepage occurred on the western and northwestern margins of the lagoon and parallel to the barrier between the lagoon and sea. These observations imply geologic controls on seepage. The combination of remote sensing and in-situ radon measurements allowed us to effectively map groundwater discharge areas across the entire lagoon. Combined, broad-scale qualitative methods built confidence in our interpretation of groundwater discharge locations in a large, dynamic coastal lagoon. |
