Transmissivities are least in a wide band parallel to the south flank of the Northside Range. The aquifer dips and thickens southeastward toward the ocean and is thinnest in this wide band. The principal recharge to the Kingshill aquifer is from infiltration of an estimated 3 percent of the precipitation that falls on the aquifer and is not lost to evapotranspiration. Some recharge also is from streams, especially during periods of storm runoff, when the altitude of the water in the stream is above that of the water table. Some water from runoff of the Northside Range may enter the aquifer at its contact with the volcaniclastic and sedimentary rocks.
Water readily moves into the permeable alluvium and into fractures in the marl and limestone.
A shallow gradient also is shown by the broad contour spacing along the south coast. The gradient changes probably reflect permeability changes in the aquifer related to fracturing, thickness of alluvium, and the presence of the more permeable post-Kingshill carbonate rocks along the south coast. Discharge from the Kingshill aquifer is largely to wells and to the ocean, but some water also probably discharges to streams during high stages of the water table. Evapotranspiration also accounts for some discharge of water where the water table is less than 20 feet below land surface. A freshwater-saltwater interface occurs where the aquifer meets the sea.