Page 30 - Beaumont Basin Watermaster

Section 3
Status of the Basin and Administration of the Judgment

3.6 Changes in Groundwater Levels in the Beaumont

Basin

3.6.1 Analysis of Groundwater Level Changes
Changes in groundwater flow and groundwater levels between 2012 and 2013 were
evaluated using a calibrated groundwater flow model that was previously developed to
reevaluate the safe yield of the Beaumont Basin (TH&Co, 2014). For this analysis, the
existing calibrated model was updated with groundwater pumping, recharge, and
groundwater levels through the end of 2013. A model-generated groundwater contour map
was created for Fall 2013 and compared to the model-generated Fall 2012 groundwater
contour map in order to evaluate changes in groundwater flow patterns and basin-wide
changes in groundwater levels. The model-generated groundwater contour maps for 2012
and 2013 are shown on Figures 3-5 and 3-6, respectively.

Groundwater flow within the Beaumont Basin generally depends on location with respect to a
groundwater flow divide which occurs in the center of the basin approximately coincident with
the Noble Creek drainage. West of the Noble Creek drainage, groundwater generally flows
to the northwest and ultimately towards San Timoteo Wash. East of the Noble Creek
drainage, groundwater flows to the southeast towards the City of Banning. The groundwater
flow directions did not change significantly between 2012 and 2013.

Basin-wide groundwater level trends in the Beaumont Basin were evaluated based on
hydrographs from seven key wells and the groundwater level change map developed by
subtracting the 2012 groundwater surface from the 2013 groundwater surface (see Figures
3-7 and 3-8). In the northwest portion of the basin, groundwater levels declined slightly
between Fall 2012 and Fall 2013. In the north central portion of the basin (TW-1),
groundwater levels declined in the beginning of 2013 but rose back up by the end of the year
in response to artificial recharge at the Noble Creek Recharge Facility. In the south-central
portion of the basin, groundwater levels at Oak Valley No. 1 increased in 2013 after declining
in 2012. At Beaumont-Cherry Valley Water District (BCVWD) Well No. 2, groundwater levels
remained stable until the end of 2013 where they began to increase. At Banning Well C-4
(southeast Beaumont Basin), groundwater levels have declined since 2012.

3.6.2 Analysis of Change in Groundwater Storage

Basin-wide change in groundwater storage between Fall 2012 and Fall 2013 was analyzed
as a function of the difference in groundwater levels across the basin and the specific yield of
the aquifer sediments. Groundwater level change across the basin was analyzed using the
following procedure:

1. The Fall 2012 and Fall 2013 model-generated groundwater contour maps were each
converted into three-dimensional raster surfaces.

2. The basin was discretized into 140-ft by 140-ft grid cells.
3. Attributes were assigned to each grid cell including groundwater level change and
specific yield.

Beaumont Basin Watermaster 2013 Annual Report – DRAFT August 2014 3-10