I'm working on a 3D regional model. I got some trouble to reach the default convergent criterion when I'm running the model. So, I tried different strategies :
1) I converge perfectly when I put the boundary conditions only on the first layer (Constant head) and this way make perfect sense. The problem is that I have in incorrect mass balance. I mean, there is no imbalance, but the flow rate that coming from the boundaries is too high in proportion with the recharge...and here is the problem. It's not normal to get ''artificial'' water from the boundaries.
2) If I copy the constant head on the second layer, I cannot reach the convergence criterion, but the mass balance is ok....it drops by 4 order of magnitude.
The result with these two simulations is very different in some region. So which one is the best ? Should we prefer to reach the convergence or should we prefer to get a correct mass balance ? Some other suggestions or way to solve it are welcome.
I observed that kind of situation so many times.....
I don't have a scientific answer to your question, but I saw that situation occurred when the hydraulic conductivity on the layer 1 is very low. If it's the case, just try to reduce your K values and see what's happen.
This topic is very interesting because I built several model and it's not obvious to decide if we fix the slices. I worked on a model recently and everything was free and movable. So the calibration was almost perfect but the geometry of the model was consedirably modified. The variation was so big that It was almost unsensed to consired that model appropriate.
There are rules to define when we should use Fixed or Free and movable ? I always used fixed in my models because of the geometry but I don't know if I'm OK.....
I'm trying to use an old modflow model I created there is 3 years ago. Since this time, I changed my computer and I stored the data on a cd. Now I'm trying to open the model and there is a problem. Modflow don't want to open it. My version of Visual modflow is 3.00.16. I would appreciate if some of you can try to open it on his computer and helping me to find the problem
Create your k zones with a gis and import data (shp) in feflow. You can create on the gis diffrent zones with a little gap between. With the gis, just generate points at equal distance between all nodes on the line of the k polygons. Import data in feflow and interpolate using inverse distance weithing. This will generate a kind of contouring of your k values and the gap between the k zones will create a smoothest k distribution, allowing feflow an easier convergence
It surely depend if you run the model fully saturated. I don't know about the basic equation for case of a confined aquifer. Anyone know the difference between unconfined and confined in the mathematical solution of Feflow.