Page 31 - Beaumont Basin Watermaster

Section 3
Status of the Basin and Administration of the Judgment

4. The resulting attribute table was processed in a Geographic Information System (GIS)
for calculating the change in storage.

The specific yield distribution used for the analysis was obtained from the calibrated
groundwater flow model used to evaluate the safe yield of the Beaumont Basin, as
summarized in TH&Co (2014).

Results of the analysis show a decrease in groundwater storage within the adjudicated basin
of approximately 783 acre-ft between Fall 2012 and Fall 2013. It is noted that, as with
previous estimates of change in storage, the extreme northwest portion of the basin was not
used in the analysis because there are little groundwater level data in this area.

3.7 Operating Safe Yield

For purposes of this TM, the annual operating safe yield (OSY) describes the net infiltration
to the adjudicated groundwater basin (not including artificial recharge) for any given year. It
is noted that the OSY is different than the Operating Yield, which is a function of the unused
overlyer production (Appropriative Water) and Temporary Surplus, as described in the
Beaumont Basin Judgment (San Timoteo Management Authority v. Banning et al., 2004).

Operating safe yield is estimated based on the following equation:

OSY = ΣP + ΔS - ΣAR
ΔT

where: ΣP = The sum of groundwater production (ac-ft)

ΔS = The change in groundwater storage (ac-ft)
ΣAR = The sum of groundwater recharge (ac-ft)

ΔT = The time over which the OSY is estimated (years)

Total Beaumont Basin groundwater production in calendar year 2013 was 17,114 acre-ft
(see Table 1). Total artificial recharge in calendar year 2013 was 8,603 acre-ft (See Table 3-
4). It is noted that only the Noble Creek Recharge Facility recharge was used in the analysis
of OSY (recharge at the Little San Gorgonio Creek facility is not included because it is
outside the adjudicated area). The change in groundwater storage estimate is based on the
analysis of groundwater levels described in the preceding section. The period of time over
which the OSY is evaluated is one year. The resulting OSY is estimated as:

17,114 + (-783) – 8,603
OSY = = 7,497 7,728 ac-ft
1

Beaumont Basin Watermaster 2013 Annual Report – DRAFT August 2014 3-11