Can Airborne Ground Penetrating Radars Explore Groundwater in Hyper-Arid Regions?

Groundwater provides roughly 43% of the water used globally for irrigated agriculture. Understanding, predicting, and managing the environmental processes that define the natural capital of Earth’s changing groundwater is one of the most pressing societal challenges of the 21st century. To understand the influence of the dynamics in the vadose zone on terrestrial ecosystems, and to estimate the future sustainability of groundwater resources, a regional and eventually global assessment of water table depth is required. To enable observations of the hydrologic systems’ dynamics, the feasibility of an airborne ground penetrating radar (GPR) system is considered as a first step to effectively provide both large spatial coverage and short revisit times. Such a capability has the potential to enable large-scale surveys to directly observe the shallow subsurface hydrologic processes. To evaluate the capabilities of such a system, we start with a review of soil and subsurface material properties, with a focus on hyper-arid regions. Using first principles, results from literature reviews, and recent field measurements, we then investigate the effects of attenuation and surface clutter to identify the potential capabilities and challenges of an airborne GPR to investigate the spatio-temporal dynamics of the vadose zone. In this paper, we arrive at a qualified “yes” as an answer the title’s question. With low radar frequencies (on the order of 10 MHz or less), adequate ground clutter rejection, and medium or higher vadose zone soil resistivity, the detection of water table depths of 50 m and beyond are feasible.

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