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## Message Boards

### calculating FRACTIONS in delft3d/delwaq

JB

#### calculating FRACTIONS in delft3d/delwaq

Youngling Posts: 5 Join Date: 3/31/16
Hi,

I am trying to figure out how to calculate fractions in DELWAQ . I'm running Delft3D version 4.01.00, 10 layer model. In the D-Water Quality user manual there are instructions for calculating fractions in SOBEK, though nor Delft3D. I see two fractions options available in the Delft3D processes library, 1) fraction freshwater from constant discharge 2) fraction freshwater from variable discharge. How do I implement the fractions simulation? There are no units associated with the fractions substance. Am I to assign some arbitrary value for the fractions and treat it like a concentration? Or is it simply a matter of turning on the fraction simulation (by entering either a 1 or 0)?

The model has multiple sources of fresh inflow and a single source of saline inflow. The fresh and saline flows are boundary conditions and have variable discharge rates.

Thanks,
James

#### RE: calculating FRACTIONS in delft3d/delwaq (Answer)

Jedi Knight Posts: 156 Join Date: 1/21/13
We have automatic fraction implemented for Delft3D Fm, but not yet for the structured FLOW. We are working on a connection between the structured FLOW en the new Water Quality user interface.

For the moment, for Delft3D 4.01.00, you can make a tracer file using the processes button, and under tracer and temperature select up to 5 tracers. But since no processes are involved, you could also use your own names in the sub-file if you edit it with a text editor your self. The format is quite simple I think (example attached).

The tric is then you use one of the stracers for initinial, and give an initial concentration of 1 for only this tracer, and then use one tracer for each source that you have, and give only a concentration of 1 for this tracer at this source, and zero for the others. Then you should have a fraction calcualtion, en the sum of al fractions -should- always be 1.

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JB

#### RE: calculating FRACTIONS in delft3d/delwaq

Youngling Posts: 5 Join Date: 3/31/16
Thanks Michel your suggestion worked great!