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Dear all, I'm currently dealing with a MODFLOW simulation where the head of an unconfined aquifer changes in time. The assumption is that for a given time and in correspondence of the channel network, the head of the aquifer stays dz meters below the surface. In order to impose suitable boundary conditions, I created a TIN based on the GMS grid (i.e. the two coincide) and I let the TIN have different time step (in order to do this I first exported the TIN, modified it adding nt columns that account for the distance dz of the aquifer from the surface, where nt is the number of time step considered, and successively imported it in GMS). The information contained in the time-varying TIN are imported in the conceptual model: 1) I created a coverage for the channel network and I assigned to channels' arcs the CHD property, 2) I selected all the nodes of the channel network and I associated them the TIN. Finally I exported the conceptual model to my MODFLOW project using Map-->MODFLOW. In doing this, I kept "Constant value throughout data set time step (step function)" (I had a look at this page http://xmswiki.com/xms/GMS:Map_to_MODFLOW_with_TINs) Now, the problem is that the boundary condition in correspondence to the channel network is not time-varying, but rather the initial value is maintained throughout the whole simulation. Can you help me in finding out the problem? Thanks