Page 23 - Beaumont Basin Watermaster

Beaumont Basin Watermaster
2013 Reevaluation of the Beaumont Basin Safe Yield 3-Apr-15

boundary (see Figure 15), groundwater levels were measured in SGPWA monitoring well TW-2,
which is located north of, and on the opposite side of, the Beaumont Basin adjudication
boundary (Boyle, 1991). During the pumping test, as much as 18 ft of drawdown was measured
in TW-2 and directly correlated to pumping Well 16, indicating that there is no significant barrier
to groundwater flow between Well 16 and TW-2, even though they are on opposite sides of the
Beaumont Basin boundary, as drawn by Bloyd (1971). Geological mapping reported in Rewis et
al. (2006) placed the Banning Fault further north of the previous Beaumont Basin boundary (see
Figure 11).

Based on the results of pumping tests reported in Boyle (1991) and consistent with Rewis et al.
(2006), the hydrogeologic basin has been shown to extend north of the Beaumont Basin
adjudication boundary to the concealed extension of the Banning Fault. It is noted that the
LSGCRF, where SGPWA has historically recharged imported water, is north of the Beaumont
Basin adjudicated boundary but within the hydrogeologic boundary. Thus, artificial recharge
associated with SGPWA spreading in these basins will recharge the hydrogeologic basin and
contribute to the inflow of water into the Beaumont Basin through subsurface inflow across the
adjudicated boundary.

3.3.1.2 Banning Area

The boundaries of the hydrogeologic basin in the Banning area is complicated by numerous en
echelon faults that have been postulated based on groundwater level differences in the area
(Boyle, 1993; Rewis et al., 2006). The original faults mapped in the area by Bloyd (1971),
which became the basis for the Beaumont Basin adjudication area, are no longer recognized as
faults (see Figure 16). Rewis et al. (2006) has described the multiple faults in the southeast
portion of the Beaumont Basin collectively as the Banning Barrier Fault. The westernmost of
these faults (named Banning Barrier Fault) has been mapped to the north of the previous Bloyd
(1971) barrier based on groundwater level differences between wells 3S/1W-12L01 and Banning
Well C3 (see Figure 16). A Central Banning Barrier Fault has also been mapped based on
groundwater level differences on either side of this fault. However, further data collection and
analysis are necessary to further refine our understanding of faults and groundwater flow in this
area.

It is noted that the aquifer system on either side of the western and central portions of the
Banning Barrier Fault are included in the Study Area and associated groundwater flow model in
order to enable a complete accounting of the water balance of the Beaumont Basin Adjudicated
Area.

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