Page 35 - Beaumont Basin Watermaster

Section 3
Status of the Basin and Administration of the Judgment

subtracting the 2016 groundwater surface from the 2017 groundwater surface (See Figures
3-6 and 3-7). The total change in storage between the Fall 2016 and the Fall 2017 is shown
in Figure 3-8. In the northwest portion of the basin (YVWD 34 and Singleton Ranch 7),
groundwater levels remained stable in CY 2017. At Tukwet Canyon Golf Club C,
groundwater levels continued a steady decline in 2017 that has been observed since 2003.
When evaluated on a long-term basis, groundwater levels in wells in the western portion of
the basin have shown a general long-term decline since approximately 2005.

As shown on Figure 3-9, groundwater levels in the north central portion of the basin rose as
much as 15 ft in 2017 as a result of increased recharge at the Noble Creek Artificial
Recharge facility. Conversely, groundwater levels in TW-1, located on the northeast corner of
the recharge facility began to recover slightly in early 2017 before starting to decline again.
This well is perforated in the lower aquifer and typically shows a delayed response to
groundwater recharge relative to wells perforated in the upper aquifer.

In the south-central portion of the basin, groundwater levels at Oak Valley No. 1 declined by
over 10 feet since 2016. At BCVWD Well No. 2, groundwater levels rose in February 2016
but have generally been declining since. At Banning Well C-4 (southeast Beaumont Basin),
groundwater levels were rising in April, declined in the summer, and began increasing in
October.

The variability of groundwater levels at BCVWD Well No. 2 and Banning Well C4 are likely
due to seasonal pumping patterns in these areas. Groundwater levels in the northeast
portion of the basin (335714116565002) have been trending upward since 2010 and have
remained mostly stable in 2017.

3.6.2 Analysis of Change in Groundwater Storage
Basin-wide change in groundwater storage between Fall 2016 and Fall 2017 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 2016 and Fall 2017 model-generated groundwater contour maps were each
converted into three-dimensional raster surfaces.
2. The basin was discretized into 100-ft by 100-ft grid cells.

3. Attributes were assigned to each grid cell including groundwater level change and
specific yield.
4. The resulting attribute table was processed in a Geographic Information System (GIS)
for calculating the change in storage.

The specific yield distribution used for the analysis was obtained from the calibrated
groundwater flow model used to evaluate the Safe Yield of the Beaumont Basin, as
summarized in TH&Co (2015).

Beaumont Basin Watermaster 2017 Annual Report – DRAFT – February 2018 3-12