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mina.88

Errors in Model checker

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Hello all,

I created 3-D lithology model in Rockwork software and I imported that as layers to GMS, in this model i have 13 layer from 1090 to 970 elavation, and the boundary has specific head and no flow condition, image attached. i want to run model at steady state. but when i run the check simulation, the model has a lot of error in first layer until 6 layer like these errors

Error: The Changing Head Boundary Condition is below the bottom elevation of cell i=1, j=13, k=1, in stress period 1.

Error: The Changing Head Boundary Condition is below the bottom elevation of cell i=1, j=14, k=1, in stress period 1.

Error: The Changing Head Boundary Condition is below the bottom elevation of cell i=1, j=16, k=1, in stress period 1.

Error: The Changing Head Boundary Condition is below the bottom elevation of cell i=1, j=17, k=1, in stress period 1.

Error: The Changing Head Boundary Condition is below the bottom elevation of cell i=1, j=18, k=1, in stress period 1.

Error: The Changing Head Boundary Condition is below the bottom elevation of cell i=1, j=19, k=1, in stress period 1.

Error: The Changing Head Boundary Condition is below the bottom elevation of cell i=2, j=10, k=1, in stress period 1.

Error: The Changing Head Boundary Condition is below the bottom elevation of cell i=2, j=11, k=1, in stress period 1.

Error: The Changing Head Boundary Condition is below the bottom elevation of cell i=2, j=12, k=1, in stress period 1.

Error: The Changing Head Boundary Condition is below the bottom elevation of cell i=2, j=13, k=1, in stress period 1.

Error: The Changing Head Boundary Condition is below the bottom elevation of cell i=2, j=14, k=1, in stress period 1.

Error: The Changing Head Boundary Condition is below the bottom elevation of cell i=2, j=15, k=1, in stress period 1.

Error: The Changing Head Boundary Condition is below the bottom elevation of cell i=2, j=16, k=1, in stress period 1.

Error: The Changing Head Boundary Condition is below the bottom elevation of cell i=2, j=19, k=1, in stress period 1.

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How can i solve this errors?

I appreciate if anyone help to solve this problem.

sincerely

mina

post-48161-0-69082400-1441686727_thumb.p

Edited by mina.88

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Mina,

I suspect you have specified head cells with the head elevation set below the base of the cell, which causes a terminal error. Use the automatic layer assignment option to ensure the elevations are set at the uppermost cell ("Auto assign to one cell") or the uppermost and all underlying cells ("Auto-assign including lower cells") where the elevation is above the base of the cell. If you are using transient heads, be aware that automatic layer assignment seems to use the elevations from the first stress period.

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Mina,

I suspect you have specified head cells with the head elevation set below the base of the cell, which causes a terminal error. Use the automatic layer assignment option to ensure the elevations are set at the uppermost cell ("Auto assign to one cell") or the uppermost and all underlying cells ("Auto-assign including lower cells") where the elevation is above the base of the cell. If you are using transient heads, be aware that automatic layer assignment seems to use the elevations from the first stress period.

Hello Dear Rob,

Thanks a lot for quick respond. i have one boundary coverage and i set ("Auto assign to one cell") so all of errors removed but i don't know how assign ("Auto-assign including lower cells") for all underlying cells in boundary coverage,

Also I have two problem in my model:

1- I define recharge coverage for first layer but the model could not estimate that after simulation and the recharge value is zero in Flow budget and i don't know why?

2- in well coverage i have problem too, all of wells don't have any screen data, then i define layer range from the watertable to last layer in every well and i divided Flow rate to layer numbers and set them in their filed, but the model cant estimate flow rate in wells accurately after simulation in flow budget .

Do you have any idea?

Thanks in advanced .

mina

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mina - I hope you figured things out. You have a few issues which are related. It looks like you were initially setting your specified heads lower than the bottom of your cells. Besides not allowing the model to run, if you got through that issue, you may have still dried out your top layer, resulting in your recharge not being applied anymore (it doesn't get applied to a dry cell). Depending on the rest of the model design, you may need to decrease your hydraulic conductivities to "hold the water" in the upper layer, so that it doesn't dry out and allows your recharge to work. Note that your starting heads should also be set to keep that upper layer wet at the beginning.

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mina - I hope you figured things out. You have a few issues which are related. It looks like you were initially setting your specified heads lower than the bottom of your cells. Besides not allowing the model to run, if you got through that issue, you may have still dried out your top layer, resulting in your recharge not being applied anymore (it doesn't get applied to a dry cell). Depending on the rest of the model design, you may need to decrease your hydraulic conductivities to "hold the water" in the upper layer, so that it doesn't dry out and allows your recharge to work. Note that your starting heads should also be set to keep that upper layer wet at the beginning.

mina - I hope you figured things out. You have a few issues which are related. It looks like you were initially setting your specified heads lower than the bottom of your cells. Besides not allowing the model to run, if you got through that issue, you may have still dried out your top layer, resulting in your recharge not being applied anymore (it doesn't get applied to a dry cell). Depending on the rest of the model design, you may need to decrease your hydraulic conductivities to "hold the water" in the upper layer, so that it doesn't dry out and allows your recharge to work. Note that your starting heads should also be set to keep that upper layer wet at the beginning.

Hello sean,

yes that's right. the top layer is dry but when i use ''Recharge at highest active cell''option in recharge Package , the program can estimate the Recharge correctly. and all of specified heads in boundary defined for second layer to last layer. is that correct?

Also i defined ''layer range'' for observation wells in conceptual model but in the attribute table i have ''layer'' column too, I dont know what is that?

Any suggestions will be great.

Thanks in advance.

mina

Edited by mina.88

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The "Recharge at highest active cell" should work in applying the recharge to the layer below dry cells. ...but you need to first correct any errors you have with your specified heads being below the bottom of a cell. In those cases, go to the cells where this error occurs and get rid of the specified heads (the specified heads in the lower layers will then all be correct and drive the model).

Regarding the observation well issue, under the coverage setup, you should have a "3D grid layer option for obs. pts." and you would select either "By layer number", "Use well screen", or "By z location" - each one will give you a different attribute table. In the "by layer number" option, YOU would define what layer the observation point is in. By z location would be you defining the z elevation for the point in the box outside of the model window. The model then would apply it in the correct layer.

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The "Recharge at highest active cell" should work in applying the recharge to the layer below dry cells. ...but you need to first correct any errors you have with your specified heads being below the bottom of a cell. In those cases, go to the cells where this error occurs and get rid of the specified heads (the specified heads in the lower layers will then all be correct and drive the model).

Regarding the observation well issue, under the coverage setup, you should have a "3D grid layer option for obs. pts." and you would select either "By layer number", "Use well screen", or "By z location" - each one will give you a different attribute table. In the "by layer number" option, YOU would define what layer the observation point is in. By z location would be you defining the z elevation for the point in the box outside of the model window. The model then would apply it in the correct layer.

ok sean and thank you.

when i choose "By z location" option , the model has this errors'' the following observation wells were out side of the model grid and were not written to the *.hob file.'' so i choose "By layer number" option. but i couldn't understand, i have 2 option one of them is" from layer and to layer '' that i defined those as water layers and another one is layer and i don't know how defined that?

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Okay, now I see what is going on. In your coverage setup, uncheck the box "Layer Range" under Sources/Sinks/BCs. Then you will only have the single column for the layer to which the point belongs.

Dear sean,

Thank you very much for you'r helping.

acording to you'r idea, At first i corrected any errors that related to specified heads being below the bottom of a cells. and i difined initials head in first layer. in model checker, i dont have any error. periviosly this model run as one layer but now my model is a multiple layer with 4 materials includ of Coarse grain, Medium grain, Fine grain and Bedrock that divided into13 simulation layers and they are assigned with different boundary condition (specified and no flow boundary condition) with same hydraulic conductivities in vertical and horizontal directions and i dont khnow why my model has dried in many layers, Do you have any idea for preventing of dry cells in many of layers??

if it possible can i have you'r email address

Best Regards

mina

Edited by mina.88

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