Page 33 - Beaumont Basin Watermaster - 2015 Annual Report

Section 3
Status of the Basin and Administration of the Judgment

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 2015 was 12,926 ac-ft (see
Table 3-3). Total artificial recharge in calendar year 2015 was 3,476 ac-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 earlier in this TM. The period of time over which the OSY is
evaluated is one year. The resulting OSY is estimated as:

12,926 + (-1,679) – 3,476
OSY = = 7,771 ac-ft
1

It is emphasized that the OSY, as presented herein, is based on one year of data. When
evaluated on a long-term basis, this methodology can be used to estimate the long-term Safe
Yield of the basin, as defined in the Beaumont Basin Judgment. As required by the
Judgment, the Safe Yield of the basin was reevaluated in 2014.

It is also noted that there are a number of data limitations that could impact the OSY
estimate. These limitations include:

• Accuracy of Overlyer Production Data – Production data from many of the Overlying
Parties is not metered but is estimated based on a water duty method (Wildermuth
Environmental, 2012). In addition to inherent limitations in this methodology, there
are, in some cases, discrepancies between groundwater production estimated using
the water duty method and production reported by individual parties to the California
State Water Resources Control Board. Resolution of Overlyer Production is
anticipated to affect the OSY (plus or minus) on the order of hundreds of acre-ft (not
thousands).

• Change in Storage Calculation – Although groundwater storage change estimates will
always have inherent uncertainty, it is possible to develop more representative results
through collection and analysis of additional data. These data include:

9 Static groundwater levels from dedicated non-pumping wells. There is evidence
that groundwater levels measured in some wells had not recovered fully between
pumping cycles in the well and were not, therefore, representative of true static
conditions. This can be addressed by waiting longer after pumping to collect

Beaumont Basin Watermaster 2015 Annual Report – Final – December 2016 3-12