Page 37 - Beaumont Basin Watermaster

Section 3
Status of the Basin and Administration of the Judgment

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
in the basin to help achieve a better calibrated model, resulting in more accurate
groundwater head distributions. Bettering our understanding of the hydrogeology
of this area will help improve the accuracy of the model and its output.
3.8 Recommendations

The Rules and Regulations, initially adopted in June 2004, were developed with the
understanding that they should be revisited and/or revised from time to time to make sure
they were consistent with the provisions of the Judgment. Revisions to the Rules and
Regulations have been made over the years with the latest revision changing the reporting of
Watermaster activities from a fiscal year basis to a calendar year basis.

Currently, Watermaster is conducting a study to estimate groundwater losses from the basin
resulting from spreading of imported or outside water at selected locations in the basin. The
report is anticipated to be completed in eary 2018.

Watermaster may conduct additional studies in the future in support of:

Beaumont Basin Watermaster 2017 Annual Report – DRAFT – February 2018 3-14