High-resolution aerial infrared mapping of groundwater discharge to the coastal ocean
Limnol. Oceanogr. Methods 11:262-277 (2013) | DOI: 10.4319/lom.2013.11.262
ABSTRACT: Submarine groundwater discharge (SGD) is a principal pathway for nutrient and contaminant entry into coastal zones worldwide. The ability of SGD to transport dissolved constituents, and the spatially and temporally variable nature of SGD, require rapid and high-resolution data acquisition at the scales in which it is commonly observed. Airborne thermal infrared (TIR) remote sensing is uniquely qualified for this task, and is applicable wherever > 0.1 °C temperature contrasts exist between discharging and receiving waters. We investigated SGD on three of the largest Hawaiian Islands, including most of Oahu, much of western Hawaii, and most of western Maui. The resulting images are 0.5 to 3.2 m-resolution sea-surface temperature maps that are accurate to 0.7 °C. In this article, we lay the foundation for a complete methodology of TIR data collection, post-flight data processing, and image interpretation for groundwater discharge research. We demonstrate that groundwater plume areas are linearly and highly correlated to in situ groundwater fluxes. These results illustrate the potential for volumetric quantification and up-scaling of small- to regional-scale SGD. These methodologies provide a tremendous advantage for identifying and differentiating point-source and diffuse groundwater discharge into oceans, lakes, and streams. The techniques are also important precursors for developing best-use strategies for time-consuming in situ studies, and represent a substantial new asset for those concerned with coastal-zone research, planning, and management.