Issue with FluxFile and OverlandFlowPFB in ParFlow

[Akhil Jnanadevan]

Dear All,

I am currently working on setting up a ParFlow model and encountered an issue related to recharge boundary conditions.

When I prescribe recharge using FluxConst, the model works as expected and infiltration occurs. However, when I try to prescribe the same recharge values in my model using FluxFile or OverlandFlowPFB, the model remains dry.

The flux input file is a .pfb file applied to the top patch, containing values of recharge specified as mass flux (L/T) × density, consistent with the ParFlow Richards’ equation formulation. Each value is given with a negative sign to indicate flow into the system. Since my ultimate goal is to provide a spatially non-uniform recharge field, I created and tested with a uniform recharge .pfb file for clarity. Even then, the model does not respond, whereas it does when using FluxConst.

I am performing a spinup run with the subsurface set initially dry, and using OverlandFlowSpinUp = 1. With FluxConst the groundwater responds, but with FluxFile/OverlandFlowPFB it does not.

Could you kindly advise on whether this is related to the way FluxFile/OverlandFlowPFB is applied in ParFlow, or if there are specific considerations I may be missing? Any guidance or references would be very helpful.

Thank you very much for your time and support.

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Thanks and Regards

AKHIL J
Research Scholar (PMRF)

Water Resources Engineering
Department of Civil Engineering
Indian Institute of Technology (IIT)  Delhi
Alternate Email: cez228131@civil.iitd.ac.in
Ph no.: +91 8891555774