The major source of recharge to the unconfined part of the aquifer in the southern part of the valley is infiltration of streamflow from Prather and Butte Creeks. Water enters the aquifer as leakage from natural channels, unlined diversion canals, and two small storage reservoirs. Another recharge source for the southern end of the valley is subsurface inflow from the west and south. Minor amounts of recharge are from infiltration of precipitation and irrigation return flow. In other parts of the valley, the unconfined part of the aquifer is recharged by direct precipitation, subsurface inflow, and irrigation return flow. The confined part of the aquifer is recharged almost entirely by subsurface inflow from the north, west, and south.
Flow in the unconfined part of the aquifer is generally from west to east (fig. 135), whereas flow in the volcanic rocks that contain water under confined conditions is toward the center of the valley from the north, south, and west and then toward the east (fig. 136). The potentiometric surfaces shown in figures 135 and 136 indicate that the hydraulic head of the unconfined part of the aquifer is higher than that of the confined part at Mahogany Mountain, which is the eastern boundary of the valley. Because this is not a major recharge area, the downward hydraulic gradient and west-to-east flow in the valley suggest that ground water leaves the valley as flow through the volcanic rocks beneath Mahogany Mountain and flows toward Klamath Lake and the Klamath River in the adjacent valley to the east.