Definition of runoff thresholds integrating satellite data and in-situ measurements: results from Voineşti Experimental Basin (Romania)

Abstract

Understanding runoff-controlling mechanisms requires hydro-meteorological data derived from experimental plots or catchments. The present study focuses on the Voineşti Experimental Basin (VEB - Romania), which is in the Curvature Subcarpathia and is characterised by outcropping continental fluvial deposits. VEB has different experimental plots built to understand the relations between runoff and its genetic and predisposing factors. The study analysed the monitoring data in a plot of 600 m2 covered by grassland. An empirical model defined the runoff threshold by integrating ground data and satellite estimations. By identifying 45 runoff events in the 2016-2018 period, it was possible to define a runoff threshold considering the rainfall depth and the antecedent soil hydraulic conditions. Two indices were used based on the previous volumetric water content and the antecedent degree of saturation retrieved by the Copernicus Sentinel-1 mission. By adding the rainfall depth to the soil antecedent hydraulic conditions, a runoff threshold of about 65-67 mm was identified. These findings encourage using satellite moisture products to describe hydrogeological processes in scarcely instrumented areas.