Head OF Old riVer Barrier installatiOn and FlOWs - San Joaquin ...

of 3 m from the bubble curtain. The light is generated
by an array of LED strobe lights that create white light
in a vertically orientated beam of 22º beam width. This
allows the light beam to be projected onto the rising
bubble curtain. The narrow beam angle minimizes light
saturation of the area surrounding the BAFF. This served
to reflect the beam and improve visibility from the
direction of approaching fish.
Installation of the BAFF began on April 7th. After the
BAFF was deployed, four (4) underwater hydrophones
were deployed (Figure 4-6) to provide for 2D tracking
in the vicinity of the BAFF. Each hydrophone was
connected to an on-shore receiver capable of tracking
the acoustic tags implanted in the juvenile Chinook
salmon by the VAMP Fish Monitoring Program. The
receiver and hydrophone array was constructed by
the same manufacturer as those used in the VAMP
receiver network so the acoustic tags could be detected
at the HORB and throughout the Delta by VAMP. Each
VAMP acoustic tagged fish transmits an underwater
signal or acoustic “ping” that sends identification
information about the tagged fish to the hydrophones.
The hydrophones around the HORB were deployed in an
array at known locations that maximize spacing of the
hydrophones in two dimensions. For two dimensional
tracking, tags pings must be received on at least
34 / 2009 Annual Technical Report
Figure 4-9
Physical Structure of the Bio-Acoustic Fish Fence (BAFF) Similar to that Deployed at the Divergence
of the San Joaquin River and Old River During the 2009 VAMP.
three hydrophones. Figure 4-6 shows a typical twodimensional
(2D) track of one tagged salmon smolt as
it approaches the BAFF. The smolt shown in Figure 4-6
passed through the BAFF while the BAFF was off.
The hydrophone array cannot provide a 2D position
behind the BAFF when the BAFF is on because a ping
must be received on three hydrophones to provide a 2D
position. When the BAFF is in operation, hydrophones
2, 3, and 4 (see Figure 4-6) are unlikely to receive a ping
because the bubble curtain portion of the BAFF blocks
sound passage.
A full report on the efficiency of the BAFF is in
preparation at the time of this report writing. Initial
results however show that the BAFF appears to be
very efficient (>80%) in deterring acoustically tagged
fish from entering Old River. The testing of the BAFF
was during a period of time when the flow split was
averaging 75% down Old River (Table 4-1). When the
BAFF was off, it appears only 25% of the tagged salmon
smolts remained in the mainstem San Joaquin River, a
value similar to that found by Holbrook et al. (2009) in
2008 when no barrier was present and the flow split was
68% down Old River and 32% down the mainstem San
Joaquin River.