San Benito County Water District San Benito County Water District

These are listed on Figure 1 with the respective DWR basin numbers. With the exception of
the Bitter Water Valley (which drains generally south to the Salinas River Valley) and the
Panoche and Vallecitos valleys (which drain to the east toward Tulare Lake), the groundwater
basins drain northward as part of the San Benito River and Pajaro River systems. This report
focuses on the southern part of the Gilroy-Hollister Valley groundwater basin.
Figure 2 shows groundwater basin boundaries in the northern portion of San Benito County.
The three DWR-defined subbasins include the Bolsa, Hollister, and San Juan Bautista Areas.
Figure 2 also shows the boundaries of eight subbasins that were originally delineated in 1996
for the District annual reports: Bolsa, Bolsa Southeast (SE), Pacheco, Hollister East, Tres
Pinos, Hollister West, and San Juan subbasins, and the Llagas subbasin in Santa Clara County.
These subbasin boundaries are based on a combination of infrastructure (CVP subsystems),
political boundaries (Zone 6), and geologic structures (faults). This definition of subbasins is
maintained in this report, supporting consistent analysis and reporting of groundwater
conditions.
Local Surface Water. Figure 1 also shows the locations of the two reservoirs owned and
operated by the District. Hernandez Reservoir (capacity 17,200 af) is located on the upper San
Benito River in southern San Benito County. Paicines Reservoir (capacity 2,870 af) is an
offstream reservoir between the San Benito River and Tres Pinos Creek. It is filled by water
diverted from the San Benito River, with some of the diversions consisting of natural runoff
and some consisting of water released from Hernandez Reservoir. Water stored in the two
reservoirs is released for percolation in Tres Pinos Creek and the San Benito River to augment
groundwater recharge during the dry season.
Central Valley Project. The District also purchases Central Valley Project (CVP) water from
the U. S. Bureau of Reclamation (USBR). The District has a 40-year contract (extending to
2027) for a maximum of 8,250 af/yr of municipal and industrial (M&I) water and 35,550 af/yr
of agricultural water. The District negotiated the renewal of this contract in May 2007. As part
of this renewal, a separate repayment plan for existing capital costs was agreed upon, such that
capital costs are not included in the cost per acre-foot of purchase water. San Justo Reservoir
(see Figure 1) is used exclusively to store and regulate imported CVP water and has an
operating capacity of 7,000 af.
The imported water is delivered to agricultural, municipal, and industrial customers in the
Pacheco, Bolsa Southeast, San Juan, Hollister East, Hollister West, and Tres Pinos subbasins
through 12 subsystems containing approximately 120 miles of pressurized pipeline laterals.
Since 2003, a portion of the M&I water has been treated at the Lessalt water treatment plant,
which allows direct use of CVP water for municipal supply purposes by Sunnyslope County
Water District (Sunnyslope CWD) and the City of Hollister.
Annual Groundwater Report for Water Year 2008 December 2008
San Benito County Water District 3