Extraction well and sphere of influence

[Jeremy Croes]

Dear GMS forum,

I would like to make a very simple model of an extraction well.

The purpose is just to visualize the influence sphere and the drawdown.

The well is suppose to extract 20 m³/h, but only operate 6 hours a day.

For this reason I'm trying to do it in a transient state as a steady state model gives errors.

What would be the most simple way of doing this?

The no-flow boundaries of the model have a very large distance from the well, so that they could not effect the well.

Furthermore all layers except top are set as confined.

I have also tried implementing a mirror well far from the extraction well, so that influx matches outflux.

But the sphere of influence is then altered and not symmetrical as one would expect.

Thank you for any help!

Jeremy

[Sean Czarniecki]

Make sure you have recharge across the model domain.

[Jeremy Croes]

Thank you for the response.

I would like to produce the model without setting recharge.

But just to check if it reproduces the error, I also modelled the same simulation with recharge.

This still results in an error, mostly that the model does not converge.

[Sean Czarniecki]

If you are taking water out of the model, you need to be putting some in, or everything will dry up. As you noted, an injection well changes your drawdown shape. You need to have enough recharge to offset the withdrawal and it would be distributed evenly across the model to get an even drawdown.

In addition, if your starting heads are too far off from your solution, you could run into problems.

One more thing - make sure to run the model checker to see if you have everything in the model you need.

[Jeremy Croes]

Thanks again for the reply.

I have checked the model with the model checker and found nothing unusual.

I tried simulating the model with different amounts of recharge. Still get the same problem.

I will check if changing the starting heads might help.

Thanks again for the response