floating point overflow error in MT3DMS

[indraja p]

Greetings to all

I am new to MODFLOW and need to estimate ground water quality for the study region having Bay of Bengal as the eastern boundary and river as the western boundary. The coastal areas are affected by sea water intrusion. I need to simulate ground water quality under various pumping scenarios using MT3DMS transport model.

For which a basic modflow model was created for the study area and water levels were calibrated and simulated. Now for quality, in addition to that concentration observation wells (TDS value was given), bulk density, species parameters, initial concentration, dispersion, recharge concentration, constant concentration data were given as input and some particles were added in the coastal region. with those parameters the modflow, modpath and mt3dms were run and it shows floating point overflow error in both the steady and transient state conditions for MT3DMS.

what might be wrong either. please suggest me to overcome this error. your guidance is extremely needed for my research work.

with regards.

[Jakab Andras - Gmail]

This kind of error may occur if the program is trying to write a number that is too large in magnitude. It is hard to tell what could be the main reason, but it's most likely attributable to an MD3DMS convergence issue and the 32-bit version of both the GUI and the core programs; i.e., I noticed that you are using an extremely old Visual MODFLOW GUI that runs a 32-bit version of the core programs. So, in addition to digging deeper for the source of the problem you may also consider reverting to a newer version of the GUI, potentially Visual MODFLOW Flex.

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[Luther]

Several things can cause this. If you have a constant concentration source very close to the area where you are applying the recharge (as in, the model top), it can cause this issue. What solution technique are you using for the advection term? The MOC and HMOC can have issues with point overflow errors. 

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[indraja p]

Thank you for the suggestion sir. I will try using visual modflow flex.

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[indraja p]

I am using the MOC in advection method. Which method can be used instead of MOC to overcome this issue. Please suggest any other changes that can be made to run MT3DMS successfully.

Thank you so much for the response.

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