Radar Probing of groundwater in Hyper-Arid Environments: understanding Aquifer dynamics in high discharge area

The North African Sahara and the Arabian Peninsula are the largest nonpolar deserts on Earth, occupying ~10% of the Earth?s land surface. These deserts are some of the harshest and most arid climates on Earth, with almost half of their surface receiving less than 200 mm/yr of precipitation. During climatic wet periods, the last of which occurred about 7,000 years ago, precipitation in the Sahara was approximately 50?100% higher than today. This paleo-precipitation formed the main part of the current groundwater system (referred to as fossil aquifers) in this extended area. Given the lack of surface water, these aquifers represent a critical regional resource. However, the distribution and dynamics of these aquifers are poorly known, let alone understood; the main reason is that current knowledge relies on measurements from local wells that are sparsely distributed and cover only a few percent of the desert area. We propose to substantially increase knowledge on the distribution and dynamics of these aquifers by using satellite and surface radar data to augment the sparse data from local wells. Specifically, we will use Caltech?s existing 40-MHz low frequency sounding radar to map the depth of the water table, hydraulic head and boundaries in selected areas. That data will be combined with InSAR monitoring by TerrasSAR-X, COSMOSKY-Med and RadarSAT2 to assess the amplitudes and boundaries of the ground deformations induced by the rapid discharge of these aquifers. These technologies will be used to map the ground deformation associated with water table depth variation over specific segments of the North African and coastal aquifers in Morocco and Oman respectively where high discharge rates are observed from well logs. We will map the depth of the water table and explore the radar capability to monitor the water freshness from signal decay measurements in high discharge zones. Faculty from the Sultan Qaboos University in Oman and Hassan II University in Rabat, Morocco will collaborate on this project, including data collections, data analysis and science publications. Both organizations are members of the USAID Middle East and North Africa Network of Water Centers of Excellence (MENA NWC). The collaborators will contribute to the selection of study sites, which will be based on their scientific research and monitoring priorities, logistics and field access approvals. The joint work will result in a better understanding of the use of low frequency radar for large scale mapping of subsurface hydrogeological features and improving the current water table depth maps delineating the unknown boundaries in highly discharging areas for these aquifers. Sounding radar and InSAR observations will be provided to the Centers of Excellence to start a data record that will enable continued modeling of aquifers dynamics. Planned science publications along with knowledge transfer will position the MENA NWC collaborators to successfully compete for future international funding opportunities to continue this critical regional science.