[Hydro Modeler]

I typically handle this situation by cutting cross sections through the storage area and then use an inline structure to create the storage area. You will probably have to "fake" the cross sections in the storage areas to achieve the desired elevation-capacity relationship unless you have this information. I should mention that I don't actually use the "storage areas" that are available in the model, but rather create an area that will store water behind the weir using cross sections.