Modelling heat exchange of a stratified lake - Lake - Delft3D
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Lakes and reservoirs are important resources for communities around the globe. They provide food, drinking and irrigation water and can also offer spots for recreation. Under certain conditions lakes can also represent a threat for local communities, such as flooding or limnic eruptions. The ecological state of shallow lakes may be hampered by suspended sediments due to wind driven currents and waves. In deep lakes, stratification can cause undesirable anoxic conditions in the deeper areas. Understanding these systems is crucial to enable a sound management of these water bodies.
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Modelling heat exchange of a stratified lake
Marcin Kawka, modified 7 Years ago.
I am trying to model an eutrophic and stratified small lake in Delwaq. Simulation period covers the whole summer so heating of top layers of water column (total depth 30meters) plays an important role. At the same time temperature limits the growth of algae and algal bloom creates turbidity in top layers which limits light extinction. I use Z-layers and hydrodynamic results from delft3D and wind-induced cooling (DelTRad) which affects the top layer.
As far as I understood the TEMPERATURE process description from Technical Reference Manual radiative heating is only possible "at dry flats" which is obviously not my case. So my question is: is it possible to include radiative heating of water not through the sediment? Or alternatively can at least I use modelled temperature from Delft3d in Delwaq? It's not perfect (no turbidity feedback) but it's closer to the reality. I attach plots of temperature for three different layers from both delwaq and delft3d for comparison.
Thank you in advance
It seems you just found a chapter in the DELWAQ Technical Reference Manual that needs some update.
To compute water temperature in DELWAQ you can activate the HeatBal process. HeatBal takes solar radiation as input a.o. and should meet your needs. As mentionned, HeatBal is not described yet in the Tech. Ref. but in the meantime you can have a look at the source code (file heatfl.f) or simply configure HeatBal through the PLCT GUI.
As for your second question, you can indeed use FLOW computed water temperatures. Among the DELWAQ input files produced by your z-layered FLOW model you should find a com-*.tem file. You can use this file as binary input to define a so-called segment function in DELWAQ (see section 7.3.4 of the DELWAQ input file description).
Hope this helps.
Marcin Kawka, modified 7 Years ago.
Thank you Christophe, this clarifies a bit.
So I opened PLCT editor to define HeatBal process for my simulation, I went through the general processes which might be associated with HeatBa (Temperature, Meteo, etc.)l, but I was unable to find HeatBal - is it hidden somwhere?
I tried to use PLCT in developer mode. When I try to add New Process for Water Temperature by entering Process ID: HeatBal I am able to add it (Program warns me that It will remain on the list only if influences ModTemp), and then when I try to save the GUI crashes.
I'm using Delft GUI 4.01.00.ohmw.rc07 and PCLT 5.04.01.29071 under windows, but I simulate under Linux with DELWAQ 5.01.01.2703M, my proc* files are:
1 995 820 Jul 15 17:18 proc_def.dat
42 652 Jul 15 17:18 proc_def.def
You don't need to open the PLCT in developper mode. HeatBal is an existing process. I wrongly guessed it would be a separate processes you could activate instead of the defautl one but it's actually the standard temperature module. So you simply need to select the substance "Water Temperature" and check the process "Temperature and heat exchange". One of the input items of this process is a switch that let's you choose to model absolute (0) or exces (1) temperature. The default is 1 so you need to make this parameter editable when editing the process in the PLCT and then change the value to 0 in de Delwaq GUI.
I'm modeling the temperature stratification in a shalow lake, but the model didn't represeting the stratification. Can you have some ideias why? I already change the Wind drag Cof., the vertical vescosity and diffusivity, and a lot of other parameters.