intro story Coast / Estuary

Coast / Estuary

Coastal systems are among the most dynamic physical systems on earth and are subject to a large variety of forces. The morphodynamic changes occurring to coastlines worldwide are of great interest and importance. These changes occur as a result of the erosion of sediments, its subsequent transport as bed load or suspended load, and eventual deposition. 
 
Estuaries are partly enclosed water bodies that have an open connection to the coast. Estuaries generally have one or more branching channels, intertidal mudflats and/or salt marshes. Intertidal areas are of high ecological importance and trap sediments (sands, silts, clays and organic matter).
Within the Delft3D modelling package a large variation of coastal and estuarine physical and chemical processes can be simulated. These include waves, tidal propagation, wind- or wave-induced water level setup, flow induced by salinity or temperature gradients, sand and mud transport, water quality and changing bathymetry (morphology). Delft3D can also be used operationally e.g. storm, surge and algal bloom forecasting. 
 
On this discussion page you can post questions, research discussions or just share your experience about modelling coastal and/or estuarine systems with Delft3D FM. 
 

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Sub groups
D-Flow Flexible Mesh
DELWAQ
Cohesive sediments & muddy systems

 

 

Message Boards

Ambient temperature, water temperature, and ambient natural background temp

RS
Martin Schueder, modified 5 Years ago.

Ambient temperature, water temperature, and ambient natural background temp

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

I am encountering some extremely wrong model results (such as pH >14 and TIC <0) and I think it has something to do with my water temperature. I am confused about how to specify different temperatures in the Process parameters input tab. For instance, I have selected TEMPERATUR as an active process in my .0* file, and thus in the GUI I am prompted for the following:

- Air temperature (NatTemp)
- Ambient water temperature (Temp)

and therefore I am modeling:

- Water temperature (ModTemp)

Looking at pg 416 of the Process Library Description manual I see that:

- ModTemp = modeled temperature
- T = ambient water temperature
- NatTemp = ambient natural background water temperature

In the GUI I see that:

- Air temperature = NatTemp
- Ambient water temperature = Temp

I know the absolute temperature of water at my boundary conditions, and the absolute air temperature from physical observations. What I want is a dynamic computation of the temperature of each computational volume so that all temperature dependent processes occur at the appropriate rate. If it can be avoided, I do not want WAQ to compute this water temperature, and instead I want it to take temperature from FLOW. I believe the procedure is outlined here. Regardless of if I use FLOW or WAQ to compute “Temperature”, what I am unsure of is:

- The difference between the different temperature variables, as it appears the nomenclature is inconsistent (ModTemp, T, NatTemp, Temp are all used, but it appears T=Temp. Is NatTemp air or water?), what are the strict definitions of these variables?
- Which temperature variable the kinetic rates in WAQ are dependent on? The WAQ manual says T or ambient water temperature (pg. 217). If SwitchTemp=0, then T=ModTemp (Process Library Description pg. 417). Therefore, why would I specify Temp as a (constant/known time series) process parameter in the GUI if the ModTemp (which equals Temp) is being modeled?
- Which temperature it is that will be defined by the .tem file produced by FLOW when a .tem file is used as a forcing function? Should I define Temp as a constant process parameter, which is then overwritten by the forcing function commands I write in the .inp file?

I understand this post may be confusing and I apologize for asking such a rudimentary question. I very much appreciate your help.

Thank you,

Martin
MC
Mathieu Chatelain, modified 5 Years ago.

RE: Ambient temperature, water temperature, and ambient natural background (Answer)

Padawan Posts: 28 Join Date: 12/13/12 Recent Posts
Hi Martin,
ModTemp (=modelled water temperature) is a state variable, while NatTemp (=air temperature) and Temp (=water temperature) are parameters. Finally, T is the water temperature as it is usually written in equations; in Delwaq, T=Temp.

Thus, Temp is the parameter affecting the rates of all (bio)chemical processes.

#1 If you model water temperature in Delwaq (=ModTemp) by activating the process TEMPERATUR, then you indeed don't need to specify a value for Temp.
(a) If SwitchTemp=0, then ModTemp = modeled absolute water temperature. Then, Temp = ModTemp, so that the temperature you model will be used to affect the rates of all (bio)chemical processes.
(b) If SwitchTemp=1, then ModTemp = modeled excess water temperature. Then, Temp = ModTemp + NatTemp, so that processes rates are affected by the absolute temperature.

#2 If you don't model water temperature in Delwaq, then you need to specify a value for Temp:
(a) a constant (called PARAMETER)
(b) a time-series (called FUNCTION)
(c) a spatial-varying time-series (called SEGMENT FUNCTION). Here you could use the result from your hydrodynamic simulation. You can either edit the INP-file directly, or select the *.TEM file via the GUI. In the INP-file, it will appear as a segment function:
SEG_FUNCTIONS
'Temp' ; name of segment function
ALL
BINARY_FILE 'your_hyd_run.tem' ; binary file


In case of doubt, just add Temp to your output and check its value!
Cheers,
-Mathieu.
RS
Martin Schueder, modified 5 Years ago.

RE: Ambient temperature, water temperature, and ambient natural background

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

Thank you very much for this thorough explanation! I have done as you recommended in point #2(c) and have much improved results. I appreciate your time.

Martin
MC
Mathieu Chatelain, modified 5 Years ago.

RE: Ambient temperature, water temperature, and ambient natural background

Padawan Posts: 28 Join Date: 12/13/12 Recent Posts
Very good news, I think that indeed #2c is the best way to include temperature forcing in Delwaq.
Happy modelling!
Cheers.