Hello,

I'm currently working with the DELFT3D-WAQ module and encountered an issue after aggregating and coupling FLOW with WAQ.

I tested my simulation for continuity using the UI, and WAQ(1) ran successfully. However, WAQ(2) consistently fails at exactly 1Y190D, returning Error Code 1 (NAN found in the computational array). I've attached a screenshot of the .mon file and the simulation panel for reference.

Upon checking the .mon file, I found that segment 330—which is located in the middle of the domain—was flagged, but nothing seemed unusual.

Here are some key details about my setup:

• FLOW Timestep: 1 min
• WAQ Timestep: 10 mins
• WAQ Numerical method: 11.33 (or 11.70 for testing)
• Ideal FLOW Test: When I ran a test with an idealized water level (minimal decrease, always full lake), the simulation ran without issues.
• Realistic Water Level Variation: When incorporating the actual water level fluctuations, the simulation consistently fails at 1Y190D, which coincides with the drier season when water levels decrease significantly. At this point in the simulation, the water levels in layers 1 and 2 (possibly layer 3) drop to zero.

Has anyone encountered a similar issue? Any insights on potential solutions would be greatly appreciated!

Thank you.