Inverse identification of soil properties at catchment scale via pilot point calibration of an integrated surface-subsurface hydrological model

For water managers, extreme weather events such as droughts and heavy rainfall can pose severe challenges. Both sudden and longer term surpluses or shortages of water are operationally challenging to deal with. Investigating the effects of extreme hydrological events at the catchment scale requires the development of hydrological models capable of simulating such events. The present study is focused on developing such a model for an agricultural catchment using the integrated surface-subsurface hydrological flow model (ISSHM) HydroGeoSphere. For robust simulation of the impact of heavy rainfall and drought events on water availability and crops, an accurate representation of the spatially highly variable soil hydraulic properties has been identified as crucial. To identify effective soil hydraulic properties at the catchment scale, we propose a method combining real time observations of soil moisture, groundwater levels and catchment outflow with an ISSHM of the catchment via pilot point-based model inversion. The applicability of the method is demonstrated on a 17 km² tributary agricultural catchment of the Odra River located 20 km north of Wrocław, Poland. The validation data for the approach consist of soil samples analysed both before and after the vegetation period.