Renewal of the Dutch National Hydrological Model

The Dutch National Hydrological Model currently consists of five physically different models linked together. The software components are slated for renewal which provides a rare opportunity to improve process description, flexibility, robustness, and computational efficiency of the hydrological concepts used for national simulations of the Netherlands. Through application of the current model for integrated modelling in the Netherlands we have identified three main challenges: Representative parametrization of the regional groundwater-surface water interaction Simulating highly managed large- and small-scale water bodies in integrated hydrological simulations Simulating the unsaturated zone in integrated hydrological simulations of lowland regions We will present (and would like to discuss) a 4-year PhD research plan to tackle these challenges. The Netherlands is characterized by a dense network of surface waters for drainage requiring very fine meter-scale spatial discretization, which is unfeasible for national modelling. An analytic solution will be investigated and tested across the Netherlands to find effective parameters of the groundwater-surface water interaction and to understand its scaling behavior, providing better initial estimates and more insight to judge calibration results. Secondly, a new code implementation to efficiently simulate highly managed surface water bodies in for regional and national applications, that is explicitly designed to be coupled to a saturated zone model, has been developed (Ribasim.jl, https://deltares.github.io/Ribasim/) and will be tested against measurements. We will focus on drought events, the groundwater-surface water interaction, and the trade-offs between (managed) surface water versus groundwater extraction. Finally, we will compare different unsaturated zone concepts for a representative set of Dutch soil profiles, most with shallow water tables, and investigate the potential of scientific machine learning to provide computationally efficient, explainable simulation schemes. Drought events are also the primary interest here, with the aim to eventually estimate and understand crop and vegetation impacts. The PhD project is being carried out under the Dutch Science Foundation (NWO) KIC-call Climate-robust production systems and water management which focuses on research into solutions for robust agricultural systems, designing climate-robust and valuable nature-based sand landscapes of the future, increasing freshwater availability in coastal areas and modelling, monitoring, and predicting drought.