Page 9 - Beaumont Basin Watermaster

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

1.0 Introduction

1.1 Background

The Beaumont Basin is located in the San Gorgonio Pass, a low-relief highland located between
the San Bernardino Mountains and the San Timoteo Hills in Riverside County, California (see
Figure 1). The boundaries of the Beaumont Basin (also referred to as the Beaumont Storage
Unit) were originally defined by Bloyd (1971) and adopted by the Superior Court of the State of
California (the Court), when the basin was adjudicated per Riverside County case number RIC
389197, San Timoteo Watershed Management Authority vs. City of Banning, et al. (the
Judgment) (see Figure 2). It is noted that subsequent studies of the Beaumont Basin area have
redefined the hydrogeologic boundaries of the groundwater basin (Rewis et al., 2006). However,
for purposes of this report, the Beaumont Basin refers to the adjudicated basin area as defined in
the Judgment.

The Safe Yield of the Beaumont Basin is defined by the Judgment as “The maximum quantity of
water which can be produced annually from a groundwater basin under a given set of conditions
without causing a gradual lowering of the groundwater level leading eventually to depletion of
the supply in storage.” In 2004, the Safe Yield was established as 8,650 acre-ft/year. As per the
Judgment, the Safe Yield is to be reevaluated every 10 years. This report presents the 10-yr
update in the reevaluation of the Safe Yield of the Beaumont Basin.

1.2 Purpose and Scope

The purpose of this analysis was to reevaluate the Safe Yield of the Beaumont Basin in keeping
with the requirements of the Judgment. The evaluation was conducted by developing a detailed
water balance of the basin and vicinity with the aid of a calibrated numerical groundwater flow
model.

The groundwater flow model used for the analysis was based on a model previously developed
by the United States Geological Survey (USGS) for the Beaumont area (Rewis et al., 2006).
However, in order to develop a detailed water balance and Safe Yield estimate specific to the
Beaumont Basin, as defined herein, it was necessary to refine and update the preexisting model.

The scope of the evaluation consisted of:

1. Obtaining and compiling data.
2. Updating and refining the existing USGS groundwater flow model.

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