Gate Trail Operation 31-Jan-07

 

The upstream water level was slightly increased for last 5 days of the gate trial operation.

Water levels have been manually measured by ruler at the upstream deck (5,000 EL.) and downstream sheet file (4,997 EL. (?)).  Water level was increased 0.29 ft at the upstream pool in 5 days as shown in the table below.  Water head difference between upstream and downstream was also increased.  Main reason is caused by the gate operation.  Most of the gates have been raised and thus, water level has been increased at the upstream pool, even though the river discharge has been deceased at this period as shown in the figure below (Discharge diagram of USGS Alameda Bridge station is not available for unknown reason).  

 

Date

Upstream EL. (ft)

Downstream (ft)

Head Loss (ft)

28-Jan-07

4995.04

4994.17

0.87

29-Jan-07

4995.17

4994.08

1.09

31-Jan-07

4995.33

4993.17

2.16

Difference

0.29

1.00

1.29

 

 

           

 

 

Due to the lower water level at the downstream of the dam, sand bars were shown in the west side of the channel as shown in photo below.  If this gate opening condition (only east side gates opening), sediment will be deposited to the west side soon for both the upstream and the downstream (upstream sand bars will not be shown for the high water level).

 

 

 

Sediment deposition along the fish passage seemed still washed away, although there is no measurement.   Water level at the entry of the fish passage was increased, so inflow rate to the passage and flow velocity should be increased.

 

           

Entry of the fish passage                                                                  Exit of the fish passage

 

 

Recommendations

  1. Detailed gate operations, such as opened gates (number and height) should be posted for all cases in real time base.  If this information is not acquired electrically, gate number should be attached at each gate to find out manually to check easily which gate is raised.
  2. Amount of sediment flushing along the fish passage is better to be counted in any kind of number.  We don’t need to measure a sediment concentration, but changes of sediment deposition depth and width will be a great results and evidences.