OIL-FIELD WATERS TN SAN JOAQUIN VALLEY, CAL. 9 
SAN JOAQUIN VALLEY. 
GEOGRAPHY AND DRAINAGE. 
San Joaquin Valley, a part of the great and nearly level-floored 
depression which traverses the central part of California, is bounded 
on the east by the Sierra Nevada and on the west by the Coast Ranges. 
San Joaquin River, which directly drains the northern two-thirds of 
this great valley, discharges through Carquinez Strait into San 
Francisco. Bay and thence through the Golden Gate into the Pacific 
Ocean. The southern, more arid third of the valley has no surface 
outlet under normal conditions, and the surface waters accumulate in 
the Buena Vista reservoir, near the Midway-Sunset field, and in the 
depression occupied by Tulare Lake, southeast of Coalinga. The 
streams that drain into the valley from the Sierra Nevada carry 
praotically all the surface water that reaches it, for the streams on 
the west side are shorter and practically dry during the greater part 
of the year. On this account the valley floor is unsymmetric, the 
axis or line of lowest depression lying nearer the western than the 
eastern foothills. 
A considerable portion of the drainage from the mountains sinks 
into the sand and silt of the valley floor and joins the underground 
circulation. As all the drainage from the valley must pass through 
the narrow outlet at Carquinez Strait the underground circulation 
is probably extremely slow. Mendenhall has aptly referred to the 
great central depression of California, of which San Joaquin Valley is 
the southern part, as “canoe-shaped, with only a notch in the rim at 
the straits through which the waters spill.” 1 
GEOLOGY . 2 
It is not the purpose of this report to describe in any detail the 
geology of San Joaquin Valley or of its oil fields, but a brief outline is 
necessary to a proper understanding of the conditions governing the 
chemical character and the flow of the underground water. 
Although San Joaquin Valley is essentially a great structural 
trough filled with valley wash, the geologic conditions on its east and 
west sides present many points of contrast. The east boundary of 
the valley is the Sierra Nevada, which is composed of granites and 
metamorphosed sedimentary and igneous masses of pre-Cretaceous 
1 Mendenhall, W. C., Preliminary report on the ground waters of San Joaquin Valley, Cal.: U. S. Geol. 
Survey Water-Supply Paper 222, p. 25, 1908. 
2 The geology of the oil fields of San Joaquin Valley is more completely described in the following reports: 
Arnold, Ralph, and Anderson, Robert, Geology and oil resources of the Coalinga district, Cal.: U. S. Geol. 
SurveyBull. 398,1910. Arnold, Ralph, and Johnson, H. R., Preliminary report on the McKittrick-Sunset 
oilregion, Kern and San Luis Obispo counties, Cal.: U. S. Geol. Survey Bull. 406,1910. Anderson, Robert, 
Prel imin ary report on the geology and possible oil resources of the south end of the San Joaquin Valley, 
Cal.: U. S. Geol. Survey Bull. 471, pp. 106-136, 1912. Anderson, Robert, and Pack, R. W., Geology and 
oil resources of the west border of the San Joaquin Valley north of Coalinga, Cal.: U. S. Geol. Survey Bull. 
603, 1915. 
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