Potential of SWOT for Monitoring Water Volumes in Sahelian Ponds and Lakes

Abstract

Small water bodies play a pivotal role in Sahel, as a critical source of water for livestock and people, and providers of important ecosystems services. Monitoring, modeling, and better understanding their hydrological behavior is, therefore, a key issue. The future Surface Water and Ocean Topography (SWOT) satellite mission will bring a resolution and spatial coverage breakthrough, allowing the estimation of water levels and volumes in small water bodies worldwide. This paper assesses the potential of SWOT for monitoring water volumes in Sahelian ponds and lakes. This is done by analyzing SWOT-like synthetic data produced using a SWOT simulator developed by NASA-JPL. For the Agoufou lake, water levels were retrieved with an accuracy better than 4 cm, while slightly worse results were obtained for the Zalam-Zalam lake, that has a more elongated shape. In addition, data from the global precipitation mission dual-frequency precipitation radar have been also employed to investigate the backscattering coefficient variability in the same radar frequency band (Ka-band) as SWOT. We have found that, in the study region, the contrast between water and land, dependent on soil type, soil moisture, and wind conditions, is sometime quite small which can be challenging for water masks estimation. Overall, the first application of the SWOT simulator over the Sahel has shown the good potential of SWOT for monitoring the seasonal variability of water levels and volumes in this region.