Wflow_sbm v0.6.1, a spatially distributed hydrologic model: from global data to local applications

Abstract. The wflow_sbm hydrologic model, recently released by Deltares, as part of the Wflow.jl (v0.6.1) modelling framework is being used to better understand and potentially address multiple operational and water resources planning challenges from catchment scale, national scale to continental and global scale. Wflow.jl is a free and open-source distributed hydrologic modelling framework written in the Julia programming language. The development of wflow_sbm, the model structure, equations and functionalitities are described in detail, including example applications of wflow_sbm. The wflow_sbm model aims to strike a balance between low-resolution, low-complexity and high-resolution, high-complexity hydrologic models. Most wflow_sbm parameters are based on physical characteristics or processes and at the same time wflow_sbm has a runtime performance well suited for large-scale high-resolution model applications. Wflow_sbm models can be set a priori for any catchment with the Python tool HydroMT-Wflow based on globally available datasets and through the use of point-scale (pedo)transfer functions and suitable upscaling rules and generally results in a satisfactory (0.4 ≥ Kling-Gupta Efficiency (KGE) < 0.7) to good (KGE ≥ 0.7) performance a-priori (without further tuning). Wflow_sbm includes relevant hydrologic processes as glacier and snow processes, evapotranspiration processes, unsaturated zone dynamics, (shallow) groundwater and surface flow routing including lakes and reservoirs. Further planned developments include improvements on the computational efficiency and flexibility of the routing scheme, implementation of a water demand and allocation module for water resources modelling, the addition of a deep groundwater concept and distributed computing with a focus on multi-node parallelism.