Page 23 - Beaumont Basin Watermaster

Section 3

Status of the Basin and Administration of the

Judgment

The Beaumont Basin Watermaster is responsible for the accounting of groundwater
production, recharge of supplemental water, groundwater transfers and storage activities in
the Beaumont Basin. Since the inception of the Judgment accounting has been conducted on
a fiscal year basis starting on July 1, 2003.

Through the adoption of Resolution No. 2011-01, on September 21, 2011, Watermaster changed
the accounting from a fiscal year basis to a calendar year basis starting in CY 2011. The
conversion of Fiscal Year basis to Calendar Year basis was documented in the Annual Report for
CY 2011 adopted by the Board in early 2013. The annual report for CY 2018 builds on the
information presented in previous annual reports.

3.1 Climate, Hydrology and Hydrogeology

3.1.1 Climate
The Beaumont Basin is located in a semi-arid region characterized by warm summers and
mild winters with average summer high temperatures in the mid to upper 90s (Fahrenheit) and
average winter low temperatures in the mid to low 40s. Precipitation in the region occurs as
snowfall in the upper elevations of the San Bernardino Mountains to the north and rainfall in
the Basin. Annual precipitation in the Beaumont Basin, as recorded at the County of
Riverside’s Beaumont Station 013 averaged 17.05 inches over the 100-year period between
1919 and 2018. On the average during this 100-year period, 11.91 inches of precipitation, or
69.8 percent of total, fell during the winter between December and March. Over the last 25
years (1994-2018), precipitation has averaged 14.32 inches of rain which is approximately 84
percent of the 100-year average precipitation. The 1994-2018 average precipitation is almost
one-inch lower than the 1993-2017 average (15.23 inches) since the precipitation in 1993 ws
34.8 inches which is twice the annual average precipitation. Unconfirmed totals for 2018 were
obtained from the County of Riverside for Station 13 and other weather sources resulting in an
annual precipitation of 12.11 inches. Is anticipated that this information will be confirmed for
inclusion into the final annual report.

Figure 3-1 illustrates annual precipitation at this station for the 25-year reporting period
between 1994 and 2018 including a plot of the cumulative departure from the mean (CDFM)
precipitation. This parameter is used to assess the occurrence, duration, and extent of wet
and dry precipitation cycles. Upper trending periods in the graph represent periods with above
average precipitation such as the 1993-98 period; average precipitation during this period was
22.6 inches or close to 50 percent above the long-term average. Other above average
precipitation periods include the 2003-05 period. Conversely, down trending periods indicate
periods of below average precipitation as in the 2011-18 period when average precipitation
was only 11.22 inches or approximately 78 percent of the 25-year average.

Beaumont Basin Watermaster 2017 Annual Report – DRAFT – February 2018 3-1