San Benito County Water District San Benito County Water District

RECOMMENDATIONS
This annual report is required under Section 70-7.6 of the State Water Code to include
recommendations regarding groundwater production, groundwater replenishment, CVP
imports, and water charges in water year 2009.
In 2009, the District continues to face an uncertain imported water supply as the ramifications
of the May 2007 Court decision on Delta smelt and the July 2008 Court decision on the Delta
salmonoids are materialized over the upcoming months. While CVP allocations are expected to
remain similar to those observed in water year 2008, groundwater use is expected to increase as
groundwater infrastructure is put in place to meet growing demand and users adjust their
cropping and irrigation practices to rely more heavily on groundwater. However, in past years
the District has accumulated substantial reserves in the groundwater basin that can now be
relied upon for water supply.
GROUNDWATER PRODUCTION AND REPLENISHMENT
Groundwater levels increased slightly over the past year and groundwater storage in most
subbasins is near historic highs. Groundwater storage is adequate to meet water demands in
2009 and years thereafter. As a matter of perspective, groundwater pumping over the four
drought years of 1988 through 1991 averaged 34,456 afy, similar to the amount estimated for
2009. These pumping rates resulted—as expected—in temporary groundwater level declines
(see Figure 17). The recommended amount of groundwater production for 2009 is the
amount—in conjunction with available CVP water—that meets agricultural, M&I, and
domestic water demands, assuming efficient water management practices.
Historically, the District conducted extensive percolation operations that ultimately reversed
overdraft and then accumulated a substantial water supply reserve. District management of
groundwater storage in conjunction with surface water is currently being refined to avoid
excessively high or low water levels both on a temporal and geographic basis. In 2009, storage
in Hernandez Reservoir should be replenished and percolation of available local water supplies
should be focused on areas exhibiting declines in response to drought and increased pumping.
In the longer term, the District should consider the ramifications for groundwater management
of increasingly unreliable CVP supply. While overall groundwater storage is substantial,
increasing use of groundwater is likely to result in localized declines. Such potential problems
can be minimized with groundwater management planning that addresses the distribution of
groundwater pumping relative to areas of historical high groundwater and to areas of historical
and existing percolation activities. The percolation capabilities of the latter areas (including
District access, permeable surficial sediments, and flat channel area for water spreading) may
need protection in light of intensifying and potentially competing land uses.
Annual Groundwater Report for Water Year 2008 December 2008
San Benito County Water District 46