jurisdictions. The cost to move water is
higher than the cost of the water itself.
THE CURRENT STATE
OF OUR DAMS
SCVWD District 1 includes five
reservoirs (see chart below) that are
managed by the water district under the
regulatory authority of the California
Division of Safety of Dams. Anderson
Dam is also under the Federal Energy
Regulatory Commission because it has
a hydroelectric generating facility.
Our dams were built 50 to 80 years
ago primarily for water storage and eco-
system support. A prolonged drought
depletes these surface water resources.
They also provide incidental flood
protection (all but Uvas are operated
according to a “flood rule curve,” which
restricts storage capacity). Aging dams
such as Anderson need improvements
in order to be safe and effective
resources, at capacity, during periods
of flooding or in the event of an
earthquake.
According to the water district, one
acre-foot of water (325,851 gallons) is
enough to serve two households of five
for a year, on average. South County
reservoirs (excluding Calero, which
serves North County) have a current
combined storage of over 104,700
acre feet.
ANDERSON RETROFIT
Anderson Dam was built in the 1950s
when knowledge of local geologic and
seismic characteristics was quite limited.
What we now know is that a significant
earthquake could cause the dam to fail,
releasing a wall of water that would
reach downtown Morgan Hill in about
15 minutes, and parts of San Jose
within a few hours. The dam needs a
seismic retrofit and SCVWD is taking
steps to make that happen.
The goal is to remove, rebuild, and
replace all of the dam embankment,
modify the spillway, and increase draw-
down capacity, among othe r improve-
ments. Construction is slated for 2020-
2024 with a price tag around $400
million. South County will pay about
20 percent. The other 80 percent will be
paid by North County, which derives a
greater benefit from the dam.
The winter’s fierce storms filled
Anderson beyond capacity-level restric-
tions set by the Division of Safety of
Dams. Emergency measures to draw
down excess capacity were exacerbated
by the fact that the Coyote Valley area
was already saturated. The Coyote Creek
system overflowed its banks, flooding a
number of San Jose neighborhoods.
DAM LEVELS AS OF APRIL 13, 2017
Description
Reservoir Storage
(acre-feet)
Reservoir Capacity
(acre-feet)
% of Reservoir Capacity
COYOTE VALLEY
Coyote Reservoir
23,317.9
23,244
100.6
(restricted capacity=53%)
Anderson Reservoir
63,386.4
90,373
70.1
(restricted capacity=68%)
UVAS/LLAGAS
Chesbro Reservoir 8009.2 7,945 100.8
Uvas Reservoir 9,950.2 9,835 101.2
GUADALUPE WATERSHED
Calero Reservoir
4,220.6
9,934
(supplies North County, not South County)
41.5
(restricted capacity=46%)
Source: Santa Clara Valley Water District
14
GILROY • MORGAN HILL • SAN MARTIN
MAY/JUNE 2017
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