The water filled original pore spaces. The water level in the second beaker had declined from 500 ml to 150 ml. The difference was in the sand-filled beaker. The 350 ml of water filled the pore spaces between sand grains. Permeability Permeability is the capacity of water to flow through rock or sediment.
Water can flow readily through rocks with high permeability values.
Simple animation of flow of groundwater between connected pore spaces. Note that not all pore spaces are interconnected. However, not all pore spaces may be connected while others may contain clay minerals that can expand in the presence of water to block passageways and reduce permeability. Surface water films in fine-grained materials may fill the narrow connections between pore spaces blocking the passage of groundwater. Numerous measurements of natural groundwater systems have revealed that groundwater flows much more slowly than water in streams due to the effect of friction from the surrounding grains.