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intro story DELWAQ


DELWAQ is the engine of the D-Water Quality and D-Ecology programmes of the Delft3D suite. It is based on a rich library from which relevant substances and processes can be selected to quickly put water and sediment quality models together.

The processes library covers many aspects of water quality and ecology, from basic tracers, dissolved oxygen, nutrients, organic matter, inorganic suspended matter, heavy metals, bacteria and organic micro-pollutants, to complex algae and macrophyte dynamics. High performance solvers enable the simulation of long periods, often required to capture the full cycles of the processes being modelled.

The finite volume approach underlying DELWAQ allows it to be coupled to both the structured grid hydrodynamics of the current Delft3D-FLOW engine and the upcoming D-Flow Flexible Mesh engine (1D-2D-3D) of the Delft3D Flexible Mesh Suite (or even other models such as TELEMAC).

'DELWAQ in open source' is our invitation to all leading experts to collaborate in further development and research in the field of water quality, ecology and morphology using Delft3D. Feel free to post your DELWAQ related questions or comments in this dedicated forum space. If you are new to DELWAQ, the tutorial (in the user manual) is a good place to start. A list of DELWAQ related publications is available here.




Sub groups
D-Flow Flexible Mesh

Cohesive sediments & muddy systems


Message Boards

Z-model & Sigma-model

Mirko Stefani, modified 1 Year ago.

Z-model & Sigma-model

Youngling Posts: 2 Join Date: 3/29/19 Recent Posts

Hi everyone,


I'm doing a project on a real lake using Delft3D but I still don't understand the difference between a Z-model and a Sigma-model. I understood how to implement it into the program but I can't apprehend the theory behind these two models. Hope someone can help me explaining it.


Best regards,


Richard Measures, modified 1 Year ago.

RE: Z-model & Sigma-model

Jedi Knight Posts: 178 Join Date: 3/23/11 Recent Posts

Hi Mirko,

In a standard sigma model the vertical layering is based on a proportion of the depth in each cell, thus the elevation of the divisions between layers varies between cells (due to varying bed levels and water surface levels) and also varies with time (as the water level varies).

In a Z-model the vertical layers are fixed at specific elevations i.e. the elevation of the boundaries between different layers do not change in space or time (except for tracking the water surface elevation).

In general sigma layers tend to be more stable in my experience but for specific problems (e.g. modelling stratified lakes where you want to avoid adding too much numerical diffusion) Z-layers may be preferable.

Does that make sense?