Drone applications in hydrogeophysics: Recent examples and a vision for the future

The recent boom of commercially available drone technology capable of supporting geophysical imaging systems has led to several practitioners adopting the platforms to collect geophysical data. This has led to significant opportunities for studying hydrologic systems, as these platforms enable more efficient data collection and data collection in difficult-to-access locations. Recent examples from snow and stream studies show the viability of these platforms for studying complex systems in difficult locations and the added value of data provided by the technology. Small unoccupied aerial system (sUAS) ground-penetrating radar (GPR) surveys conducted over water bodies and snow have proven beneficial for determining bathymetry in dangerous swift water and depth of snowpack in mountainous regions. Challenges arise due to decoupling of the GPR antenna and the ground surface, which limits signal penetration. Additionally, multifrequency or multichannel GPR imaging remains a challenge due to the payload limitations of an sUAS. Drone-mounted thermal infrared data collection enables the generation of thermal orthomosaic images with unprecedented detail and spatial range for quantifying groundwater fluxes to surface water bodies and reduces issues with infrared reflection common in ground-based studies. Several drone-mounted electromagnetic studies also show utility in efficient, high-resolution mapping of near-surface soil conductivity. Overall, the use of drone platforms for studying hydrologic systems remains a frontier in science applications that needs further refinement before wide-scale adoption. The preliminary studies presented here hint that the development of robust geophysical data acquisition tools based on UAS will lead to an explosion of applications to near-surface hydrologic problems.