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from about 200 to more than 400 mg/l, based on selected well data from 1985 and 1988
(Blevins, 1989).

8.5 REGIONAL GROUNDWATER USE

8.5.1 Groundwater [lg msigngtign

Eastern Hydrographic Subarea: Groundwater within the Eastern Hydrographic Subarea is
designated as having existing beneficial uses for municipal and domestic supply, industrial
service and process supply, and agricultural supply (RWQCB, 1975a). No potential
beneficial uses are in effect for groundwater in this subarea.

Sylmar Basin Subarea: Groundwater in Sylmar Basin Subarea, as well as all of the Upper
Los Angeles River Area, has been established as being of existing beneficial use for
municipal, agricultural, and industrial service and process supply purposes (RWQCB, 1975b).

8.5.2 Groundwater Quantity

Eastern Hydrographic Subarea: Groundwater storage in the alluvium within the Eastern
Groundwater Basin of the Santa Clara River valley has been calculated at approximately
176,400 acre-feet (Slade, 1986). Useable groundwater in storage within the Saugus
Formation underlying a large portion of the Santa Clara River valley area was calculated

to be approximately 1.41 million acre-feet (Slade, 1988). This approximation was based on
the volume of groundwater stored only in the potentially useable Saugus aquifers in the
500-foot to 2,500-foot depth zone (Slade, 1988).

Sylmar Basin Subarea: Data for 1988 reported groundwater storage of approximately

310,000 acre-feet for the confined aquifers of the Sylmar Basin Subarea (Blevins, 1989).
These same data indicated a +371 acre-feet change in storage for 1987-1988 compared to
a cumulative storage change from 1954-1955 through 1987-1988 of -21,575 acre-feet.

8.5.3 Groundwater Production

Eastern Hydrographic Subarea: Water use within the Upper Santa Clara River valley,

which encompasses much of the Eastern Hydrographic Subarea, was projected by the

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