SaltiSolutions

SALTISolutions is a research program that focusses on salt intrusion in deltas. Within Wageningen University, two PhD students work on the fourth project within the larger program: Salt Dispersion across scales and design of Counter Measures.

SALTISolutions will deliver the VirtualDelta, a digital twin of a real Delta, as management and design instrument for salt-intrusion related questions in deltas worldwide. Increasing salt intrusion caused by human alterations of estuaries and deltas, increased freshwater demand, and climate change threatens freshwater availability in deltas. Freshwater supply is essential for health and human well-being, for ecological integrity of aquatic ecosystems, and for economic interests (16% of Dutch national direct production depends directly on freshwater supply). An integrated and optimized societal response to salt intrusion challenges demands actions at several levels. Short time scales: operational management tools based on short-term forecasts and available (‘big’) data for freshwater management. On medium time scales: evaluation of effects of infrastructural changes on salt intrusion and, using scenario models, introduction into the society-stakeholder debate. Development of well-designed, cost-effective and environmentally-friendly solutions to salt intrusion based engineering (‘grey’) and nature-based (‘green’) solutions is essential. On long time scales: evaluation of climate-proofness of infrastructure, policies and mitigation measures. Extreme climate-change scenarios require radically new solution pathways.

SALTISolutions’ Virtual Delta brings together advanced models, data-assimilation tools, visualization methods, stakeholder-interaction tools, and exploratory strategic analyses for delta management at different levels. Scientific challenges and expected scientific breakthroughs include: incorporating multiscale physical processes; understanding impact of natural eco-morphological processes on salt intrusion, and developing forecasting systems and advanced game approaches for stakeholder engagement and decision making. Technology suppliers and end-users are actively involved in SALTISolutions, strengthening the global competitive position of Dutch companies. This leads to conceptual and operational breakthroughs in freshwater management of deltas.

Aims
The WUR part of the project focusses on the improvement of fast operational models for real-time prediction of salt intrusion. It takes a data-driven point of view, and will collect critical data allowing the improvement of model formulations and parameterizations for a channel network. They will focus on lateral processes at the plot scale, controlling the exchange with intertidal zones and harbors. The field observations will be used to improve critical aspects of operational models, and at a longer time scale provide a basis for the first-order estimation of the effect of counter measures. Additionally, they will measure and analyze data at the scale of the network, by focusing on tidal propagation and river discharge-tide interactions associated with salt intrusion. They will use the combined data sets to explore salt dispersion across scales.

Individual projects

Henk works on the modelling of salt intrusion. For operational control and crisis management, fast salt intrusion prediction models are essential to prevent damage to industry, agriculture, drinking water and ecology. These forecasting models usually consist of 1D network models, in which regions of complex flow are critical for salt intrusion at large scales. However, these complex regions are also particularly hard to capture in real-time forecasting models, due to a lack of knowledge of the essential mechanisms and an oversimplification of geometric effects at play. Henk will focus on a specific type of complex regions: tidal channel junctions. The goal is to better understand salt exchange processes at tidal channel junctions and propose novel parameterisations that capture the essential three-dimensional dynamics to be used in advanced one- dimensional models. Firstly, he will focus on understanding the relevant processes of salt dispersion and exchange at channel junctions by analysing data and by systematically studying the shallow water equations and their solutions. An idealised, nonlinear, subtidal (which means averaged over a tidal cycle) 3D model will be derived and implemented, inspired by the available data. The idealised model will be systematically analysed, and results will be compared to complex state-of-the-art operational 3D models, resulting in new parameterisations, describing the channel junction flow and salinity dynamics. These parameterisations are formulated into nodal point relations and are used to improve real-time, data-driven channel network models that forecast salt intrusion at the channel network scale.

More information about Daan‘s project will follow soon.

Output

van Keulen, D., Kranenburg, W. M., & Hoitink, A. J. (2025). Tidal trapping and its effect on salinity dispersion in well-mixed estuaries revisited. Estuaries and Coasts, 48(6), 153. https://doi.org/10.1007/s12237-025-01579-0

van Keulen, D., Kranenburg, W. M., & Hoitink, A. J. F. (2025). A New Harmonic Regression Approach to Interpret and Predict Estuarine Salinity Variation. https://doi.org/10.1029/2024JC022185

Jongbloed, H., Vermeulen, B., & Hoitink, A. J. F. (2025). Physics‐informed estimation of tidal and subtidal flow fields from ADCP repeat transect data. Water Resources Research, 61(1), e2023WR036038. https://doi.org/10.1029/2023WR036038

H. Jongbloed, H.M. Schuttelaars, Y.M. Dijkstra, P.B. Donkers, A.J.F. Hoitink. (2022). Influence of wind on subtidal salt intrusion and stratification in well-mixed and partially stratified estuaries. Journal of Physical Oceanography, 1997. https://doi.org/10.1175/jpo-d-21-0291.1