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.

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3D z-model: Different free surfaces in FLOW and DELWAQ

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Hi all,

I'm trying to model a reservoir using a 3D z-model configuration with Delft3D-FLOW and DELWAQ, applying the tag_6118.

Firstly, I ran hydrodynamics using the z-model and 12 layers with a Zthreshold of 0.1 m. As displayed in the attached figure 'flow_Zthr_10cm.png', hydrodynamics results of the free surface look fine. At the beginning (0 to 6 km), a free surface elevation above 0 m is observed due to the flow discharge and the river bathymetry and, after this section, a free surface drop around 0 m is observed because of the reservoir bathymetry.

Secondly, I ran water quality with two configurations of the Z-layer model processing:

1) Using the same threshold as in the FLOW, this is 0.1 m. The attached figure 'delwaq_Zthr_10cm.png ' shows the free surface and segments obtained by DELWAQ:
CONSTANTS ACTIVE_Emersion DATA 1.0 ; switches process 'on'
CONSTANTS ZThreshold DATA 0.1 ; threshold in m.

2) Using a non-threshold, this is 0.0 m. The attached figure 'delwaq_Zthr_0cm.png ' shows the free surface and segments obtained by DELWAQ:
CONSTANTS ACTIVE_Emersion DATA 1.0 ; switches process 'on'
CONSTANTS ZThreshold DATA 0.0 ; threshold in m.

According to these results (all of them are for the same date), it looks like DELWAQ is not able to handle free surface elevation above 0 m, or at least, in the way I'm setting up my model. On the one hand, if the Zthreshold is activated to 0.1 m, DELWAQ is avoiding the free surface above 0 m. In fact, results show a kind of flipping of the free surface in the river section. On the other hand, if the Zthreshold is activated to 0.0 m, the free surface is biased to 0 m along the whole model domain, generating a fictitious free surface and, consequently, fictitious diffusion gradients.

Following these comments, do you have any idea to preserve the free surfaces (water elevations) computed by Delft3D-FLOW in DELWAQ when these are above and below 0 m at the same time in the same domain?

Thanks in advance and regards,
Javier
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Attachments: delwaq_Zthr_0cm.png (83.1k), delwaq_Zthr_10cm.png (83.1k), flow_Zthr_10cm.png (88.8k)
RE: 3D z-model: Different free surfaces in FLOW and DELWAQ
Answer (Unmark)
6/20/17 11:38 AMas a reply to Javier F Bárcena.
Hi Javier,

> According to these results (all of them are for the same date), it looks like DELWAQ is not able to handle free surface elevation above 0 m, or at least, in the way I'm setting up my model.

I think this is just something going wrong in QuickPlot. Elevation above zero is somehow fliped into the negative again. I have no idea why this is. One idea that comes into mind, in QP there is an 'Operator' that could be switched from none to abs. Maybe this got in the way?

In Delwaq itself there is not a known absolute position in the vertical, only the order of segments in the vertical. You might want to look at 'LocalDepth', as the depth from the water surface to the bottom of this segment at this layer. You could try to plot this in this side view.

Michelle
RE: 3D z-model: Different free surfaces in FLOW and DELWAQ
Answer (Unmark)
6/20/17 11:39 AMas a reply to Michelle Jeuken.
P.S.: cant look into this without data