Any ideas about "decline continuously" TN& TP?

EFDC_Explorer
1

Dear all, I find my simulated TN and TP declined all the time (with no fluctuation), while the observed one not (see figures below). The boundary conditions are not that patterns, and the station is at the centre of the lake, which is far from inflow/outflows. Have someone met the problem like mine? Any idea is welcome.
TN.png
TP.png
Chla.png

2

Without knowing more about your model it is hard to say. Are you sure your boundary conditions account for all of the mass loadings of N and P into your system?

3

Dear Tom, I checked my TN, TP boundary conditions (see figures below), and compared it with the published report. It seems that the mass between report and model is approximately the same. So I assume that will it because the sediment resuspension? In “TP_SS.png” of this lake which I find in one paper, the suspended solids relates closely with TP. I want to find where can we simulate this relationship in EE? I only find one parameter “KPO4P: Partition coefficient for sorbed/dissolved PO4 to TSS or TAM”, and I set it as 0.01. I set this value according to the parameter in Ji’s LOEM model.Unfortunately, after done that, I have the “decline continuously” TP and TN result. Or should I open the “full diagenesis model”?

4

T X,At this stage, you have a fairly complex model already. I would recommend against adding any more complexity to the model before you’ve chased down all the possibilities for what is going on with the modules you have running currently. In general, it is good practice to slowly build up the complexity of your model, rather than going straight to a more complex one. Based on your posts over the last several months though, it seems like you have done that.While parameter values used in other studies are a good benchmark, I would encourage you to conduct a sensitivity analysis of the various parameters which affect N & P. If you are confident the boundary conditions are correct, this will give you a more complete picture of how the processes within the model are affecting the results you are seeing.Sorry that I can’t provide you with a clearer answer.Tom

5

Thanks Tom. I wish to ask one last question: when trying to calibrate water quality, can we first “close the algae module”, to see how N,P change without algae? And then we simulate the algae, and calibrate the algae parameters?