EO AFRICA - Quantifying Soil Moisture from Space-based Synthetic Aperture Radar (SAR) and Ground-based Geophysical and Hydrological Measurements

In the framework of the ESA EO AFRICA initiative, the R&D Facility in collaboration with European Space Agency (ESA) and the African Union Commission (AUC), launched at the end of 2021 a call for research proposals to support African-European collaborative efforts to develop innovative, open-source EO algorithms and applications adapted to African solutions for African challenges. Abstract:

Soil moisture (SM), which is the water content in the soil, plays an essential role in agriculture activities. With climate change and global warming, water scarcity is exacerbating in many parts of the world. Africa is facing the most significant challenges of water stress because food production and security depend on those water resources. Thus, monitoring SM at high resolution is of vital importance for irrigation activities, estimation of crop yields, and food security. Our study focuses on a 100-meter resolution soil moisture product, whose resolution is suitable for agriculture studies, as this is a characteristic size of an agricultural parcel. We investigate the feasibility of using use Sentinel-1 C-band Synthetic Aperture Radar (SAR) data recorded in the VV (vertical-transmit, vertical-receive) polarisation to retrieve 100m SM every 12 days and combine it with ground high resolution (cm) measurements collected twice a day to both validate and improve the estimate. The innovation of our approach is the integration of large-scale satellite data with field-scale ground geophysical measurements, such as electrical resistivity tomography (ERT) and active multichannel analysis of surface waves (MASW), and point observations such as time domain reflectometry (TDR) to downscale the SM results both in space and in time.