Page 34 - Beaumont Basin Watermaster

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

Benchmark years for estimation of land use areas included 1974, 1980, 1989, 2002 and 2010 (see
Figure 7). As municipal pumping in the Beaumont area began in approximately 1935, return
flow recharge was assumed to start at this time and was increased linearly to 1974. Likewise,
return flow between the benchmark years was increased linearly over time based on the land use
areas estimated for the benchmark years.

Based on an analysis of groundwater level trends in BCVWD Wells 1 and 2 (see Figure 27),
return flow is estimated to reach the groundwater table approximately 25 years after the water is
applied at the land surface.

4.1.5.6 Return Flow Attributable to Appropriators

Total return flow was subdivided between the Appropriators in accordance with the portions of
their service areas that lie over the Beaumont Basin adjudicated area (see Table 5). Return flow
was estimated for each Appropriator by multiplying the various land use areas (measured using
Geographic Information System software based on the land use maps described above) by their
respective return flow rates (in acre-ft/acre), as summarized in Table 3 (see Appendix D).
Table 5 shows the year in which the return flow water was applied at the land surface and the
year that the return flow was/is estimated to reach the regional groundwater table (25-yr lag).
For example, return flow estimated based on 1985 land use conditions reached the groundwater
table as recharge in 2010. Table 5 projects annual return flow, by Appropriator, through 2037 in
accordance with historical land use conditions.

It is noted that return flow occurs in some portions of the Beaumont Basin adjudication area that
are not within an Appropriator service area. These areas consist primarily of golf courses and
parks. Return flow attributed to these areas is accounted for in the “Other” column of Table 5.

4.1.6 Artificial Recharge
Artificial recharge is accomplished within the Study Area via the Little San Gorgonio Creek
Recharge Facility (LSGCRF) and the Noble Creek Recharge Facility (NCRF) (see Table 6;
Figure 9). The SGPWA began spreading imported State Project water in the LSGCRF in 2004.
As of December 2012, 9,391 acre-ft of imported water had been spread at the LSGCRF and
42,244 acre-ft had been spread at the NCRF for a total of 51,635 acre-ft. Although both of these
facilities are within the Study Area, only the NCRF is within the Beaumont Basin adjudication
area (see Figure 9).

Studies conducted by the USGS have shown that it takes 3.75 to 4.5 years for water spread at the
land surface to reach the upper aquifer groundwater table at the LSGCRF (Flint et al., 2012).

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