Page 36 - Beaumont Basin Watermaster

Section 3
Water Quality Conditions

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

Total Beaumont Basin groundwater production in calendar year 2018 was 17,279 ac-ft (see
Table 3-3). Total artificial recharge in calendar year 2018 was 12,621 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 analysis. The period of time over which the
OSY is evaluated is one year. The resulting OSY is estimated as:

17,279 + 173 – 12,621
OSY = = 4,831 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 2013. The Safe Yield will be reevaluated again
in 2023.

It is noted that the change in groundwater storage used to estimate the annualized Safe Yield
is based on a calibrated model, as described herein. As additional hydrogeological data are
collected and incorporated into the model, it can be refined to produce more representative
groundwater storage change estimates. 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 ac-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 w ell and were not, therefore, representative of true static
conditions. This can be addressed by waiting longer after pumping to collect
groundwater levels or constructing/designating non-pumping groundwater
monitoring wells in strategic areas.

9 Measurement of surface water flow in selected drainages, hydrogeological data
near Noble Creek and San Timoteo Creek, and hydrogeological analysis of faults

Beaumont Basin Watermaster 2018 Annual Report – DRAFT - February 2019 3-14