Satellite-Based Monitoring of Drought at the Watershed Scale

Drought is a complex and multivariate phenomenon influenced by diverse physical and biological processes, as this derives from the accumulative effects of climatological and hydrological variables over a certain period. Worldwide, droughts are becoming a very frequent phenomenon, also in regions historically not affected by them, such as Poland. To tackle this phenomenon and investigate its drivers, multiple approaches are being developed, based both on in-situ data and satellite-based observations, also thanks to recent advancements in numerical modelling and spatio-temporal resolution of satellite data. Focusing on the Vistula River basin in Poland, the present research uses selected drought indexes to infer spatio-temporal changes of drought over the last few decades. The opportunity to use the freely-available satellite information, processed with Google Earth Engine, allows for deriving trends at the watershed scale, providing spatially-distributed medium to long-term changes. The present analysis shows that, nowadays, drought is a major concern also for a country that used to be wetter in the past.