The following report on the Temporary Barriers Project is for your information and action, as appropriate. This report will be transmitted whenever changes occur to the operation of the barriers, and as a result of modeling and/or field monitoring of water levels in the south Delta.
STATUS AS OF: October 26, 2007Head of Old River Barrier (HORB):
On September 27, DFG requested DWR install the fall HOR barrier. This barrier will block much of the water entering Old River to help increase SJR flows past Stockton and improve dissolved oxygen in the Deep Water Ship Channel for the benefit of salmon. The barrier contractor began work on Monday, October 8. Closure of the barrier was obtained on October 18. Removal of the HOR barrier will begin early to mid-November, depending upon the need to continue operating the barrier for dissolved oxygen improvements and the final removal schedule for the agricultural barriers. We are coordinating the removal schedule with DFG and South Delta Water Agency staff.
Agricultural Barriers (Old River near Tracy [ORT], Middle River [MR], Grant Line Canal [GLC]):
All agricultural barriers are in place with the GLC and MR barriers have been operating normally. No flap gate changes were made this week. Currently, at the ORT barrier, a total of six culverts have flap gates tied open (allows tidal flows to move both ways) and three have flap gates untied (opening and closing with the tides). We will continue to monitor water levels and quality, and adjust the status of the culvert flap gates depending on conditions. Barriers were notched in mid-September in the center of their weirs to allow increased weir flow depths and improve passage for adult salmon migrating upstream.
Modeling was done to monitor water levels at various locations. The modeling shows water levels fell dramatically after the HOR barrier was closed to just above or at the level of concern at the ORT, and GLC monitoring stations (0.0 feet MSL) and the level of concern at the MR station (0.3 feet MSL). Levels quickly began rising again with the improved tidal conditions. We will closely monitor water levels and open culverts at the HOR barrier to improve water levels if conditions warrant it. We may also untie flap gates at the ORT barrier to help with water levels if water quality conditions are acceptable.
Click here to see modeling outputs
The dramatic drop in water levels after the HOR was “closed” on October 18 coincided with a dramatic drop in tidal stage at Antioch (both low-low and high-high tides)(possibly due to weather conditions). The drop in water levels was not solely due to closing the HOR barrier.
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Mark A. Holderman, P.E.
Chief, Temporary Barriers Project and
California Department of Water Resources
Phone: (916) 653-7429 FAX: (916) 653-6077
Cell/Pager: (916) 601-6036 E-Mail: email@example.com