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intro story DELWAQ

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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D-Flow Flexible Mesh
DELWAQ

Cohesive sediments & muddy systems

 


Message Boards

Implementing bottom growth / algae cover

DK
Danker Kolijn, modified 5 Years ago.

Implementing bottom growth / algae cover

Youngling Posts: 10 Join Date: 11/4/14 Recent Posts
Dear DELWAQ community,

I am currently modelling a coastal domain with very dense macroalgae growth covering large portions of the sandy surface. These algae have a considerable impact on nutrients in the nearshore. I believe the daily temperature and light exposure in the shallower portions of the model should be influenced by these algae.

At the moment I have a z-layer model being fed by currents/waves from a FLOW model. I have defined my bed layers as S1 (0.05m) and S2 (1.0m) where i've used a spatial QUICKIN map to define gC/m2 in layer S1 (~45gCm/2) and in my water column (2gC/m3). However, after running the model and viewing vertical profiles, I feel that the algae is having little effect. I wonder whether this is because the S1 layers has not been activated by the wave-driven shear stresses? Perhaps there is no exchanges happening between the water column and layer S1?

Is there another way to define algae on the bottom surface instead of in layer S1 which would have more of an exposed impact? Has anyone ever had trouble with this type of scenario?
Any recommendations is much appreciated.
Regards,

Danker Kolijn
RS
Rudy Schueder, modified 5 Years ago.

RE: Implementing bottom growth / algae cover

Padawan Posts: 52 Join Date: 10/8/13 Recent Posts
Hi Danker,

I too am working on a project that involves modeling benthic macroalgae, although in a shallow lake and not a coast. In my experience there are two options. In BLOOM, you can use fixed ULVA species to model macroalgae that extend from the sediment into the water column. In DYNAMO, you can use Diatoms in layers S1 and S2 as fixed algae species. I expect based on your referencing of S1 and S2 that you are using benthic diatoms in DYNAMO currently? I have found that using both formulations will have significant effects on the overlying water quality. My current biomass density of S1 diatoms is ~15 gC/m2, a density I also prescribed using QUICKIN.

Have you looked at primary production of your algae? Are they in fact growing and/or respiring? I know that if you do not specify a value for the parameter "PPMaxDiaS1" in your input file, then benthic diatoms will not grow, because by default the maximum growth rate is set to = -1 and is not included in the substance file.

Rudy
DK
Danker Kolijn, modified 5 Years ago.

RE: Implementing bottom growth / algae cover

Youngling Posts: 10 Join Date: 11/4/14 Recent Posts
Hi Rudy,

Thanks for the response. I am indeed using DYNAMO and haven't activated the primary production feature, thanks for that tip. Do I understand correctly it's not a switch you can flip in the PLCT but has to be manually entered in block #6 of the .inp file? How much impact did your algae have on DO?

Also, i've noticed something a bit peculiar while implementing my QUICKIN generated diatoms in layer S1. In addition to algae i'm also interested in TSS (total suspended solids) which have to be activated by my wave induced shear stresses. I've defined a certain quantity of sediment on the bed and have noticed that when using the S1 map file it is barely activated, whereas when I specify the same S1 value for the whole bottom instead of using a map file, there is significantly more sediment activated and suspended into the water column. Do you have any experience with this?