I am trying to calculate evapotranspiration in my model, and I would appreciate a lot if someone could help me with this issue.

For calculating evaporation, if I am using an expression that depends of water level, when simulation is running, does  the software recalculate the evaporation rate each time step using the current water level information? I am implementing it using an expression on In/outflow on top/bottom, but it seems it considers only the initial water level for the whole period. How can I fix it?