Subduction zones are tectonic plate boundaries where an oceanic plate sinks beneath another oceanic or continental plate. Within the subducting oceanic plate, water is held both within minerals grains and between spaces within the rock, commonly referred to as pore space. Prior to entering the subduction zone, down-going plates under significant bending that drive both normal faulting and downward pumping of fluid towards the center of the plate. The volume of water within the subducting rocks has been measured using shipboard electrical imaging techniques off the coast of Central America. As subduction continues and pressures increase, this water is released from the rocks and can influence the generation of earthquakes and magmatism. The amount of water and the rate that is released from the subducting plate is controlled by the permeability of the crustal rocks, which is largely unknown. We use two-dimensional geodynamic models to predict the water within the subducting rocks, and test which rock permeability best reproduces the observed water within the subducting plate. We then use the best permeability to predict where the water will be released from the rocks at depth.