The phreatic surface
After a previous experiment, reviewers raised the question - Was the phreatic surface fully developed? The phreatic surface is commonly called the water table. It is the level in the soil where the hydraulic pressure of the water in soil pores is equal to the pressure of the atmosphere. Water in a well will rise to the level of the phreatic surface, but in the soil it rises far above that due to the capillary attraction of the soil pores. But above the phreatic surface, or water table, the soil pores are usually and partially filled with air. The question of how this affects the failure of a dam has not yet been fully determined.