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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

December 11, 2015

FAQs: The Drought and Sites Reservoir
Frequently Asked Questions

As the drought continues, DWR engineers have been monitoring storage in Northern California reservoirs. On November 9, 2015, North-of-Delta (NOD) Storage, or total storage in Trinity, Shasta, Oroville, and Folsom reservoirs, went below 3.0 Million Acre-Feet (MAF).  As shown in the figure below, NOD storage dropped below 3.0 MAF for only the third time since the reservoirs were built.  1977 NOD Storage was lowest, at 1.93 MAF. The 2015 end-of-November NOD storage (2.87 MAF) is similar to end-of-November NOD storage last year (2.80 MAF). Average end-of-November NOD storage is 6.71 MAF and total capacity at the four reservoirs is 11.51 MAF.

The Historical Total NOD Storage (pdf) shows storage, with drought periods, including the current drought highlighted in red. 

How much water could Sites Reservoir add to storage in a drought year like this?
With historic runoff, current operations, and assuming implementation of Sites Reservoir, NODOS Alternative C:

Drought1 NOD Storage Increase = 1,120 Thousand Acre Feet (TAF)
This would be a 23% improvement, reflecting additional water in storage in the four existing reservoirs and in Sites Reservoir during drought years. Sustaining additional water in storage during a drought is an essential tool for operators to support all of the water resources purposes associated with our reservoirs.

What other benefits would Sites Reservoir provide during drought?
This improved NOD storage would support a diverse set of water resources benefits. The improvements described below are happening simultaneously with the storage improvements described above.  A direct result is improved cold water pools (CWP) in the reservoirs noted previously, which support anadromous fish populations downstream of their dams.  For example, Shasta Lake’s cold water pool would be improved, resulting in improved temperatures for salmonids in the Upper Sacramento River, below Shasta Dam.

Drought1 CWP Improvement (May-September) in Shasta Lake = 280 TAF

This would be a 15% improvement during these critical drought periods

In addition to the storage and habitat improvements upstream (i.e. in and below the existing reservoirs), Sites also provides the following drought water supply benefits downstream:

Drought1 Delta Exports Water Supply Increase = 360 TAF/year
This would be an 11% improvement in deliveries during critical drought years.

1 Drought performance is determined by the average performance during historic drought periods, years 1929-34, 1976-77, and 1987-92


Proposed Sites Reservoir

The Drought and Sites Reservoir (pdf)
Historical Total North of Delta Storage (pdf)

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