We are working on a MIKE-SHE coupled MIKE-Hydro model for a small wetland in South Africa. One of the major issues is that it has zero-flux boundaries around the model domain in the saturated zone (SZ), and therefore ignores any inflow from its boundaries in the SZ. This is unrealistic as this is a very fine-scale model, and there is very likely to be movement of water subsurface into the wetland and this may well be significant. We therefore need to correct the SZ boundary conditions.
One idea to do this was to use a nested approach, building a larger model for the catchment which would then aim to simulate the boundary conditions of the smaller model domain. The reason we didn't just work with a larger model to start with is that we thought it may mask the small scale effects we were wanting to investigate. We thought this was the best approach, however we have no idea how to output the SZ flow from the larger model, to input it into the boundary of the smaller model. Given the functionality of this model and all the grids we are able to export, it must be possible to do this. But how? Can we input a shapefile and ask for a timeseries (dfs0) file to be extracted for that domain from the large model? And then input this into the SZ boundary of the smaller model? Or is there another way to do this?
I enclose a map of the region of interest showing the nested approach, the smaller model domain is indicated by the yellow polygon, and the larger model domain by the blue polygon. The scale of the map is also indicated.