Development of a 3D hydrodynamic and ecological model for Finnish waters


  • To study and develop the applicability of the COHERENS-model to Finnish waters.
  • To apply the model to Finnish coastal and inland waters.
  • To use the model as part of a model chain from the catchment area to the Baltic Sea.
  • To integrate relevant submodels - e.g. ecological - with the hydrodynamic core.


COHERENS is a research model used in SYKE for 3-D hydrodynamic modelling and transport studies. It has been developed originally for the North Sea (Luyten et al. 1999) in Belgium and has been constantly updated since then by the Royal Belgian Institute of Natural Sciences (RBINS-OD Nature). Currently the model is in its second major iteration (V2, Luyten et al. 2011) and is freely available as open source software under the European Union Public License (EUPL). The main features of the current version of COHERENS include:

  • Physical model core with sub modules for currents, salinity and temperature.
  • A state-of-the-art sediment model which describes the transport, sinking and resuspension of suspended solids.
  • A particle transport module.
  • A model coupler enabling e.g. the use of an external wave model (SWAN).
  • Support for serial, parallel and distributed computing.
  • Modular design allows further development by the user community.

The COHERENS-model can be applied in rectangular, curvilinear or spherical coordinates depending on the size of the water body. Simulations can be made in 1, 2 or 3 dimensions. The model utilizes terrain-following s-coordinates (generalized sigma-coordinates) in the vertical making the modeling of bottom-flows possible.

Past activities

The physical part of the model was included in the EMAPS intercomparison project which studied the suitability of 6 different models for eutrophication calculations in the Baltic Sea. COHERENS-model was found to perform reasonably well when using the same forcing as the other models (Myrberg et al. 2010).

The biological module of the original COHERENS V1 was initially not suitable for Finnish waters because of its relative simplicity, missing phosphorus calculation and only one algal group. One of the original aims of this project was to take the ecology and sediment sub models from the YVA-SYKE model and implement them in COHERENS. They have been found to work well in the Gulf of Finland (Kiirikki et al. 2006). The COHERENS V1 code has since been applied to several lake and coastal waters e.g. in environmental impact studies (Pien3D).

Current activities

The modernized COHERENS V2 code has been introduced into service in the recent years and the development work has continued. Highlights of the current development include the introduction of distributed computing, ice modelling and very high resolution calculations. Work has also been done to integrate the 3-D hydrodynamic model with various data sources and other models, and to develop post-processing and visualization.

COHERENS V2 has been used in various projects and studies. For example, the model has been used to simulate transport of contaminants in lakes in the CONPAT project, wastewater-sediment interaction in the N-SINK project, and is part of the Finnish coastal modelling system.
Current COHERENS activities and development include:

  • Applying the model to Lakes Konnevesi and Puruvesi and development of a fish behavioral response submodel (Freshabit EU LIFE IP)
  • Automating model setup and post-processing, integration in a virtual research infrastructure (oGIIR)
  • Studying model response to high resolution atmospheric input data

In order to understand and validate the simulation results state-of-the-art measurement techniques are used to flow data from lakes. Our main tools include current profilers (ADCP), GPS tracked drifters with real-time data transfer and high-resolution pressure sensors for surface elevation measurements.

Two international COHERENS Users’ workshops have been organized at SYKE in 2014 and 2015 bringing together modelling experts from several countries worldwide.


Kiirikki, M., Lehtoranta, J., Inkala, A., Pitkänen, H., Hietanen, S., Hall, P.O.J., Tengberg, A., Koponen, J. and Sarkkula, J. 2006. A simple sediment process description suitable for 3D-ecosystem modelling - Development and testing in the Gulf of Finland. Journal of Marine Systems 61: 55–66.

Luyten, P. J., Jones, J. E., Proctor, R., Tabor, A., Tett, P., Wild-Allen, K., 1999. COHERENS - A coupled hydrodynamical-ecological model for regional and shelf seas: user documentation. MUMM report. Management Unit of the Mathematical Models of the North Sea, 911 pp.

Luyten, P. et al., 2011. Coherens - A Coupled Hydrodynamical-Ecological Model for Regional and Shelf Seas: User Documentation. Version 2.0. RBINS-MUMM Report. Royal Belgian Institute of Natural Sciences (RBINS).

Myrberg, K., Ryabchenko, V., Isaev, A., Vankevich, R., Andrejev, O., Bendtsen, J., Erichsen, A., Funkquist, L., Inkala, A., Neelov, I., Rasmus, K., Rodriguez Medina, M., Raudsepp, U., Passenko, J., Söderkvist, J., Sokolov, A., Kuosa, H., Anderson, T. R., Lehmann, A. & Skogen, M. D. 2010: Validation of three-dimensional hydrodynamic models of the Gulf of Finland. Boreal Env. Res. 15: 453–479.

Published 2013-04-25 at 12:53, updated 2018-01-08 at 9:18