Page 20 - Beaumont Basin Watermaster
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Beaumont Basin Watermaster
2013 Reevaluation of the Beaumont Basin Safe Yield 3-Apr-15
been mapped to date (Boyle, 1993; Rewis et al., 2006). The relationship of the Banning Barrier
Faults to the Beaumont Basin adjudicated boundary is addressed in Section 3.3.1.2.
3.2 Hydrology
3.2.1 Watersheds
The Study Area transects three major watersheds: the Santa Ana River watershed, the San
Gorgonio watershed, and the San Jacinto Valley watershed (see Figure 10). Precipitation runoff
falling within the Santa Ana River watershed travels west to the San Timoteo Creek and then to
the Pacific Ocean via the Santa Ana River. Surface runoff from Smith Creek and other areas in
the eastern portion of the Study Area flow into the San Gorgonio River, which drains to the east.
A small portion of the Study Area is within the San Jacinto Valley watershed which drains south
to the San Jacinto River.
Elevation in the Study Area ranges from approximately 1,800 ft above mean sea level (ft amsl)
where San Timoteo Creek exits the Study Area to approximately 4,400 ft amsl near the northeast
corner of the Study Area. The elevations within the Beaumont Basin are typically between 2,100
and 2,800 ft amsl.
3.2.2 Climate and Precipitation
The climate of the Study Area has been characterized as transitional, with marine coastal
influences to the west and arid Mojave Desert influences to the east (Rewis et al., 2006). The
area has hot summers and cool winters. Historical annual precipitation at the Beaumont
precipitation station, operated by the Riverside County Flood Control District, has ranged from
6.4 inches in 1999 to 35.0 inches in 1978 with an annual average of 17.5 inches (see Figure 12).
Analysis of the cumulative departure from mean precipitation at this station indicates the
following trends:
The period from approximately 1885 through 1903 was relatively dry.
The period from 1904 through 1946 was relatively wet.
The period from 1947 through 1977 was relatively dry.
The period from 1978 through 1983 was relatively wet.
The period from 1984 through 1990 was relatively dry.
The period from 1991 through 1998 was relatively wet.
The period from 1999 through 2013 was relatively dry.
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