Inactive boundary condition cells in MODFLOW Posted October 11, 2018 · Edited October 12, 2018 by Magnus Dahlberg · Report reply Hey guys! I have a question regarding the "Activate cells in coverage(s)" function. I am a master thesis student and working on a model of a local aquifer, currently supplying drinking water at a rate of 2000 m3/d. The aquifer is an esker (containing glaciofluvial soils) that lies in a small valley and has a natural outlet in the sea. I am using a specified flow boundary condition to simulate the runoff entering the esker from the surrounding outcropping bedrock. However, when only the cells in the active coverages are active some of the cells that actually have a boundary condition assigned to them are inactivated (see picture). Is there a way to correct this? Thanks! Edit: The problem was that I had ticked the box "Use to define model boundary (active area)" on several coverages. Using only the sources and sinks coverage to define the model boundary solved the issue!