Ground Water Atlas of the United States -
Segment 1 California Nevada
Drainage Basins
Three hydrologic subregions coincide with drainage basins within the Central
Valley (fig. 71). These subregions are hydraulically connected and compose the
Central Valley aquifer system and associated surface-water drainages. The
northernmost subregion is the Sacramento Valley, which extends over the northern
one-third of the Central Valley and is drained by the Sacramento River. Although
the Redding Basin extends over about 500 square miles at the northern end of the
Sacramento Valley and is a topographic extension of the valley, it is not
included as part of the Central Valley aquifer system because of its separate
ground-water flow system. Adjoining the Sacramento Valley to the south is the
Sacramento--San Joaquin Delta subregion, where a network of meandering channels
has formed at the junction of the Sacramento and the San Joaquin Rivers. The
southernmost subregion is the San Joaquin Valley, which extends over two-thirds
of the Central Valley. The San Joaquin River drains the northern part of the San
Joaquin subregion; the southern part, which is called the Tulare Basin, is
characterized by interior drainage. The Tulare Basin is named for Tulare Lake, a
lake that covered much of the basin during the Pleistocene Epoch.
Under natural, or predevelopment, conditions, recharge from rainfall and
snowmelt entered the aquifer system as seepage from streams that channel runoff
from the surrounding mountains into the valley. Most recharge is at the margins
of the valley, and the ground water moves in the subsurface to lower altitudes
and discharges into surface-water bodies that drain each basin.
Back to "GEOLOGIC SETTING" - Forward
to "Aquifers and Confining Units"
Back to Central Valley aquifer system "Contents"
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