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# boundary conditions Determing boundary condition

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Hey all!

I have a question regarding boundary condition set up. I am working on a regional model of an large aquifer field which is used for drinking water purposes. Hydrologic and hydrogeologic conditions are at this stage of the research verry clear. We are dealing with open aquifer field where boundary condition is representing inflow to the aquifer from surrounding sedimentary formations.

We have calculated the infow using National groundwater recharge model and at this stage we have data of infow (Q [m^3/s]) for every cell of the boundary condition. Is it possible to calculate the needed hydraulic head in order to simulate the boundary conditions as constant head?

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Hi, I think the flow could be calculated as a difference between the head in the model cell and corresponding head at the boundary. Conductance is the proportionality constant. Therefore

Q = C (h1 - h2).

If you know the head at the boundary (in the neighboring aquifer) and in the model cell, conductance could be easily calculated from the above formula for each model cell and the flow through the boundary would be as specified for each cell.

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Hi

As Michal said, the best way in this case is to use General Head Boundary (GHB) but you need to know the conductance. This enable adjusting the flow during transient calculation based on the head difference. If you are looking at a steady state, you can alternatively use well boundary (injection) with the flow value you have at the boundary, so no need to know conductance.

I hope this helps.

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