What type of phenomenon drives the hydrodynamics column in PO4 ITS files?

Question

Dear Chris,

I am using iWaterQuality for the simulation of hydrodynamics and water quality. There is a column in the ITS files (e.g. PO4) under hydrodynamics, I was wondering if there is a document that explains how this part is calculated? or what phenomenons are driving that column in particular for nutrients?

Regards,

Ali

Answer 1

Hi Ali, each of the ITS files details the integrated change to the variable for each process.  So for PO4_its.csv.  The columns are Hydrodynamics, Mineralization, Phyto Uptake, and Sediment Flux.

The values are then the change in the timestep to PO4 during each of those processes.

Comments

Thank you so much for the quick response. I know how Mineralization, phytoplankton uptake, and Sediment flux are calculated. Now the question is how hydrodynamics make changes to PO4? Is there a document on that? Something like equations for other parameters in CAEDYM manual.

Ali

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Hydrodynamics changes for the ITS files will just be due to inflows/outflows.  

For the time-series point files changes are due to advection/diffusion

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Thanks again for the comment.
In my case, I did not define PO4 in the inflow and I do not have outflow. But I still get a considerable amount of PO4 under hydrodynamics. It is the same with the other nutrients. I set inflow DO to zero, I still get values under hydrodynamics in ITS files. Could this have other reasons such as precipitation and evaporation? if yes does that also apply to nutrients too?

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If no PO4 values are specified in the inflow conditions then a Neumann boundary condition is enforced i.e. flow entering the domain will be given a concentration equal to the value inside the domain.

Evaporation will have an impact on surface cells but should be net 0 for ITS files. Precipitation comes in with a concentration of 0 for all scalars except temperature.

There will also be numerically rounding errors that can occur.