Generalized groundwater flow patterns in a multilayer aquifer

Generalized ground-water flow patterns in a multilayer, regional aquifer system. The water table forms the upper boundary to the uppermost aquifer in the sequence, which is called an unconfined (or water table) aquifer. Although the two lower aquifers also are bounded by water tables near the land surface, the aquifers are considered to be confined because each of them is overlain and underlain by confining units. Recharge occurs to the upper, unconfined parts of the aquifer system. Groundwater discharges to streams, rivers, and creeks, through the floors of the ocean and bays, and to marshes fringing coastal waters. Source: USGS Circular 1262.