From the information I have available (the screenshots with the file
sizes and the screenshot with the output parameters for WAQ input) I
can make a rough estimation:

- You have some 5250 segments per layer and 10 layers (estimate from
the size of the LGA file - very rough - and the screenshot).

- Total number of segments: 52500; number of exchanges: ~ 3*number of
segments (three-dimensional model) = 160,000

- Per time that output for WAQ is written, that means: 4 * number of
segments for volume, shear stress, ... + 4 * number of exchanges for
flow and area (4 bytes per value). Roughly 600,000 values of 4 bytes
each => 2.4 MB

- You have a lengthy calculation: 2.5 years. It amounts to 4 times
per day, roughly 910 days. So: 3640 times.

If my estimates are reasonably accurate, you should have a total of 9
GB of data. About 8 times less than you actually have. Hm. I would
have to know the actual sizes of your model to make a better estimate.

The one thing that surprises me is the length of the hydrodynamic
calculation: unless the hydrodynamics changes a "lot" over
that period of time, you could probably select a much shorter interval
and have WAQ repeat the hydrodynamics. Could you tell us a bit more
about the system you are modelling?