storativity

When I change the storativity of a 3D phreatic surface flow-only model, the calculated hydraulic heads at the observation points do not have any change at all. What is the STORATIVITY for?

Thanks,

Zheng 

Storativity is the FEFLOW parameter for Specific Yield. Whether you see a change in your model results after changing storativity will highly depend on the model properties. It will have no influence on a steady-state model.