Querry

[sabi...@gmail.com]

Dear all esteemed members,

While converting the conceptual model to a numerical model in Visual MODFLOW, the following error is coming:

"Object reference not set to an instance of an object".

Does anyone have an idea regarding this prevailing issue? Any kind of help is overwhelming! 

Best Regards

Sabinaya

[felix ngasoh]

POSSIBLE CAUSES OF THIS ERROR

1. Incomplete Conceptual Model

   • Missing boundary conditions, recharge zones, or wells.

   • No grid defined or invalid grid settings.

2. Layer/Zone Issues

   • One or more conceptual layers are not assigned to any grid layer.

   • Missing properties like hydraulic conductivity or storage coefficients.

3. Inactive or Unassigned Objects

   • Some objects (e.g., wells, rivers, drains) are not assigned to active model layers.

4. Null or Corrupt Data

   • Empty tables or unreferenced data in property zones.

   • Corrupt project files.

5. Software Bug or Memory Issue

   • Happens sometimes after large edits without saving/reloading.

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✅ How to Fix It

1. Check Layers and Grid

• Make sure the conceptual layers match the numerical grid layers.

• Go to Model Explorer → Grid, and verify that all layers have thickness > 0.

2. Verify All Zones and Objects

• Check if all objects (wells, rivers, recharge, drains) are assigned to the correct layer.

• Remove any unused or incomplete objects.

3. Check Property Assignments

• Ensure that every layer has hydraulic conductivity, porosity, and storage values assigned.

• Incomplete property assignments often trigger this error.

4. Validate the Conceptual Model

• Use Tools → Validate Model to check for missing assignments before conversion.

5. Rebuild the Numerical Model

• If the error persists:

  • Save the conceptual model.

  • Close and reopen Visual MODFLOW.

  • Rebuild the numerical model from scratch.

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[Sabinaya Biswal]

Thank you for the prompt response. I will check as suggested.

To view this discussion visit https://groups.google.com/d/msgid/modflow/CAL8R3mWEqLo0VptDBjNzHR8jmzaxscP%2B7%3Dbr0oF%3DPPkG3-3fxQ%40mail.gmail.com.

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Best Regards

Sabinaya Biswal

Research scholar (Land and Water Resources Engineering)

Indian Institute of Technology Kharagpur

Kharagpur, West Bengal, Pin-721302, India

Tel: +917872704625

Alternate email: sabi...@iitkgp.ac.in