Numerical models calculate the flows in and out of each model cell balancing with the flows of the surrounding model cells. The numerical model calculates the potentiometric head or water level at the center of each model cell at the end of each model stress period. The model grid is the physical model area normally overlain by a rectangular grid which defines the model boundaries and model cells. The code has been widely applied to aquifers throughout the United States and the world. A perched zone is typically unconfined and at a higher elevation than the regional aquifer system.
Unsaturated conditions exist below a perched unit.
A major doctrine defining water right systems in the western United States. The Prior Appropriation Doctrine operates on a priority system, where a priority is established based on the date water is first put to beneficial use. Potentiometric head is measured using a sounder or similar depth gauge. The Potentiometric head in a well in an unconfined aquifer is at the elevation of the water table. In a well in a confined aquifer, the potentiometric head is typically at a higher elevation than the top of the aquifer due to the confining pressure.