Is it ok to set a "No flow" boundary condition on the lateral borders of my SWI model? Or should I place a "lateral flow" boundary condition?

[Denzel Montuya]

Hi everyone,

Currently doing a saltwater intrusion model using the SWI2 package but I am debating on whether I should set a "lateral flow" or "no flow" boundary condition on the sides of my model that doesn't border the GHB. If so, what package should I use for the "lateral flow" boundary condition? FHB or CHD?

Below is a top-view picture of my model:

( the green line is the border I am talking about.)

Legend:

Yellow - wells (WEL)

Cyan - rivers (RIV)

Blue - Seawater (GHB)

Green - "No flow" or "lateral flow" border(?)

Any help or insights are greatly appreciated!

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[Kenneth Ugalde]

Hi, Denzel:

I´m just a beginner with ModelMuse/ModFlow, so I´m not opinionated on the specific packages/commands.

But, I understand that the conceptual differences might be:

• NO FLOW Boundary: if the boundary is the limit of the aquifer, I mean, if there´s a clear-cut difference in materials (e.g.: quaternary sediments vs. igneous basament rock) and, thus, permeability (e.g.: actual river sands/gravels vs. older fine loess), that makes you think it´s reasonable to assume there´s negligible flow across it. In this case, you might set the "Specified Flux" boundary condition, with flow = 0.
• LATERAL FLOW Boundary: even if it´s part of the aquifer, you "don´t care" much about it (e.g.: because it´s supposed to be too far away from the parts you're interested in). In this case, you might leave the boundary "open" to eventual flow, maybe setting:
  • A "Specified Flux" boundary condition, if you know (or can estimate) the flow distribution across the boundary and along all it.
  • Or a "Specified head" boundary condition, if you know or can estimate the head distribution along the boundary, so ModFlow can calculate the inward and/or outward flow depending on the gradients.

Regards,

2025(e)ko uztailaren 14(a), astelehena (17:19:22 (UTC+2)); Denzel Montuya erabiltzaileak hau idatzi zuen: