Dissolved Oxygen > Saturation - Delwaq - Delft3D
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.
** PLEASE TAG YOUR POST! **
Dissolved Oxygen > Saturation
I'm trying to simulate eutrophication in a reservoir, but I'm having different problems. One of them is related to dissolved oxygen: after running the model, the dissolved oxygen values increase a lot and they are bigger than saturation concentration. What can be wrong?
I can share my substance file but I'm taking in account these processes:
- Algaes (1, 2 or 3 different species).
- Water temperature (Hydrodinamics output)
- Salinity (Hydrodinamics output)
Thanks in advance,
Thanks for your quick answer. I mean that the values are much bigger: Saturation level is around 10 and dissolved oxygen becamoes around 200.
Yes, I have reaeration process already active and I've change reaeration transfer coefficient with a value of 0.75. Do you need more info?
Algaes: We are calibrating them, but for instance in Blue greens, starting in 0.03 we get values of 0.6 max. However we had models where algaes dies and oxygen still grow a lot.
Depth: It depends, but it is up to 30-35 m.
Horizontal velocity: up to 0.04 m/s
Vertical velocity: Around 3x10-5
Rearation: I tried 1, 2 and 5.
Are the DO concentrations relatively uniform or does the ~200 max occur in a specific part of your model?
Do you have drying cells in your model (as a consequence of dam operation for instance)?
Can you provide the balance output (*.prn file) without lumping the processes contribution? (Output options > Balances: check Extended mass balances and uncheck lump contribution of processes.)
If the cause is a mis-configured process, then the balance output should help identify the culprit.
Yes I have some drying cells. This values are only in a certain part of the reservoir (but is one of the most important).
I have attached you the file you want.
Could you elaborate on this? Is there a smooth gradient or are the high concentrations really limited to specific segments? From your prn file I see you have observation station (57,111) and stations (57,112) (layer 1 to 35). Can it be that you see high DO values for (57,111) and not for the (57,112) stations? Assuming (57,111) is an average over all layers, that would mean values are summed instead of being averaged. But there's a lot of guessing here Can we have a look at your inp, lst and lsp files as well?
Yes, You can see a map of the reservoir (layer 8). I have to say that this is a Z model. I send you a chart of layer 8 and average.
In (57,111) I see the averaged (that is true, I sometimes see summed values instead average but not in this parameter).
I've attached you these files.
I noticed some balance errors in your prn file. Not sure what the cause is, but since you are using z-layers and have some water level fluctuation you should certainly activate the emersion process.
From section 22.214.171.124 of the input file description manual
may feature a water surface that travels through layer interfaces when water level rises or
falls like in dammed lakes. You will then need:
CONSTANTS ACTIVE_Emersion DATA 1.0 ; switches process 'on'
CONSTANTS ZThreshold DATA 0.01 ; threshold in m.
This switches the Emersion process on. This process joins the top layer with the layer
underneath if layer thickness is lower than ZThreshold and makes the new layer the top
layer. At flooding the reverse happens. If the thickness is over ’ZThreshold’ more than the
thickness of the layer underneath, then a new top layer is formed. If you are not using this
process, unpredictable results may occur for incomplete water columns.
Did you do a "continuity" simulation? Any errors in there?
If activating the emersion process does not bring any improvement, it would really help to have all of your model input. If you need an ftp to transfer it, contact me at firstname dot lastname at deltatres dot nl.
The line in the hyd-file saying
geometry curvilinear-grid z-layers
The manual actually stated that you had to add that tag by hand. I've fixed this in revision 4592 of Delft3D FLOW, so it will be written automaticly from that version on.
I have been checking my outputs in particular Continuity. I have noticed that Continuity values are very high as you can see in the figure attached. It is supposed to be around 1, right?
If you need something else maybe upload my files somewhere is a good idea.
Indeed, the continuity concentrations should remain 1 g/m3. In the figure you attached it reaches a max of 30, which means the concentrations of other substances will be multiplied by 30 too!
There isn't much that can be done without the whole input set, so I suggest you send me an email (see previous post) so I can provide you with an ftp for file transfer.
You used discharges with negative fluxes (extractions) in your FLOW model but did not include them in WAQ.
The volume of your system decreases while no corresponding mass is removed, hence the rising concentrations.
When loading the hydrodynamics in the WAQ GUI, all your FLOW discharges will be listed. You can set the concentrations of the outgoing discharges to zero as these values will not be used, but leave the flow discharge values unchanged.
Try running your model like that and look at the continuity concentrations.
It helps me a lot! The values are a bit higher than reals but they are around 30-40 max. so now it's not so bad.
I hadn't added Continuity simulation but now I do.
I'm going to do some tests and I'll let you know if I have more problems.
Thank you so much