Department of Water Resources Home

Surface Storage Investigations


Jim Wieking,
Project Manager

Dept of Water Resources
901 P St., Room 213 A
Sacramento, CA 95814
Phone: (916) 651-9279


Ted Thomas,
Public Information Officer

Dept of Water Resources
1416 9th St, Room 252-20
Sacramento, CA 95814
Phone: (916) 653-9712

May 1, 2016

FAQ:  Sites Reservoir Diversion

How much water could have been diverted into Sites Reservoir storage from this winter's storms if the reservoir existed today?


Through April 2016, using diversion criteria associated with Alternative C facilities, over one million acre-feet (maf) could have been diverted to Sites Reservoir this water year, which began October 1, 2015.  This estimated diversion amount is about 59% of the total capacity of the potential reservoir (1.81 maf) and almost double the average diversion to Sites (543 thousand acre-feet (taf)) according to operations simulations.

Diversion criteria include several daily hydrologic condition checks:

  1. Delta Status:  if the Delta is in “excess” according to DWR’s Operations Control Office.
  2. Sacramento River Flow:  if the flows of the Sacramento River at Freeport and the diversion locations are greater than the required minimums.

If these criteria are met, then diversions would be possible.  The above diversion criteria and flow data are available online from Department of Water Resources through the California Data Exchange Center and the State Water Project Operations Control Office.  This calculation assumes that all three conveyance options would be used.  The daily diversion capacities are:

    Tehama-Colusa Canal        4,158 Acre-Feet/day
    Glenn-Colusa Canal            3,564 Acre-Feet/day
    Delevan Pipeline                 3,960 Acre-Feet/day
    Total Diversion to Sites       11,682 Acre-Feet/day

For Water Year 2016, excess Delta conditions began January 6th and remain in excess as of this writing. Based on Sacramento River and Delta flow conditions, diversions for Sites Reservoir would have been allowed beginning January 7 and continuing through April 27 (112 days).  Starting April 28, Sacramento River flow was no longer above the flow necessary for potential diversion.  During the January through April period, maximum diversion was possible for 68 days.  When the Delta is in excess, diversion may be limited based upon flow requirements of the Sacramento River.  This analysis indicates that Sites Reservoir does not fill quickly during a storm, but does take advantage of the relatively long high flow conditions of the Sacramento River that occur for extended periods after larger storms. For perspective, precipitation in the Sacramento River watershed was 179%, 34%, 238%, and 72% of average for January, February, March, and April respectively.  Total potential diversion through the end of April was 1,065 taf.
Because of the recent drought, interest in Sites Reservoir performance during drought has increased.  Performance during drought is described in “The Drought and Sites Reservoir FAQ."

Percentages based on the Northern Sierra 8-Station Precipitation Index, Water Year 2016.


FAQ: Sites Reservoir Diversion (pdf)


>> back