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:  April 20 , 2007

Head of Old River Barrier (HORB):

The HOR barrier closure is expected today, a couple days earlier than originally scheduled.  Crews worked long days and through the weekends to ensure we met the April 22 deadline correspond to the beginning of the Vernalis Adaptive Management Plan (VAMP) experiment.  Work will continue on the barrier after the 22th to complete the barrier, final grading, cleanup, etc.  Culverts are open now but will be open/closed based upon modeling which will show if we can close some or all of the culverts and still protect downstream water levels.  The decision to close some or all the culverts will be made early next week after reviewing new modeling and actual conditions in the south Delta.

Agricultural Barriers (Old River near Tracy [ORT], Middle River [MR], Grant Line Canal [GLC]):

Barrier installations began April 2, 2007. At the ORT barrier site, crews closed the barrier Wednesday and will continue doing minor cleanup work.  At the MR barrier site, construction was completed April 10.  Work on the GLC barrier boat ramp began last week and now the boat ramp has been installed, leaving the middle portion open.  However modeling done this week shows that full closure of the GLC barrier may be necessary to protect water levels.  New modeling done early next week and our review of actual water level conditions will verify whether full closure will be necessary.  A preliminary request to the USFWS to close the barriers has been made today and will be followed up next week when the modeling and review is completed.


Modeling was completed this week and the results attached.  We looked at forecasts with HOR barrier culverts all open or three open and three closed.  Also, the modeling was done with flap gates tied open at the ORT and MR barriers, but in actuality, the culverts will be untied and operating tidally beginning today.  Consequently, the forecasts are probably a little lower than what we’ll actually see. Further modeling will be done early next week to see how we should operate the HOR culverts to support the VAMP but also maintain adequate water levels in the south Delta. 

Modeling Outputs:

HORB closed 4-22-07with all culvert slide-gates closed, MR closed 4-10-07, DMC closed 4-18 07, & Partial GLC completed 4-17-07
Middle River at Howard Road Bridge
Doughty Cut above GLC Barrier
Old River near Tracy Road Bridge

HORB in 4-22-07 with 3 culvert slide-gates open, MR closed 4-10-07, DMC closed 4-18-07, & Partial GLC completed 4-17-07
Middle River at Howard Road Bridge
Doughty Cut above GLC Barrier
Old River near Tracy Road Bridge


Fishery agencies and DWR will be closely monitoring conditions for Delta smelt which might effect operations of the barriers during April-May.  Changes in flap-gate operations on the culverts, delaying filling of the GLC center section, removal of the barriers, and changes to SWP/CVP export operations are all possible actions that could be taken to protect smelt if necessary.

These weekly updates are also available for your information on our website

If you know of anyone else that should be receiving this update, please let me know by email, and I'll add them to the mailing list.  Thanks!


Mark A. Holderman, P.E.
Chief, Temporary Barriers Project and Lower San Joaquin
Bay-Delta Office

California Department of Water Resources
1416 9th St., P.O. Box 942836
Sacramento, CA 94236-0001

Phone: (916) 653-7429  FAX: (916) 653-6077
Cell/Pager: (916) 601-6036 E-Mail: