Northern California Area Office

Disclaimer

The data and table above may be used and redistributed at no cost but is not intended for legal use, since it may contain inaccuracies. While this data is based on the best available estimates of reservoir operations under the different scenarios presented here, the modeling tool uses simplified operations and is intended for comparative analysis only. The data is not an exact representation of the actual operations. The United States Government, nor any of their employees or contractors, makes any warranty, expressed or implied, including warranties of merchantability and fitness for a particular purpose, or assumes any legal liability for the accuracy, completeness, or usefulness, of this information.

Alternative Comprehensive Plans (CP)

CP1

Dam Raise - 6.5 feet
Increased Storage - 256,000 acre-feet
Focus and Components - Anadromous Fish Survival, Water Supply Reliability, Dam and Reservoir Modifications and Facility Relocations.

CP2

Dam Raise - 12.5 feet
Increased Storage - 443,000 acre-feet
Focus and Components - Anadromous Fish Survival, Water Supply Reliability, Dam and Reservoir Modifications and Facility Relocations.

CP3

Dam Raise - 18.5 feet
Increased Storage - 634,000 acre-feet
Focus and Components - Anadromous Fish Survival, Water Supply Reliability, Dam and Reservoir Modifications  and Facility Relocations.

CP4

Dam Raise - 18.5 feet
Increased Storage - 634,000 acre-feet
Focus and Components - Anadromous Fish Survival, Water Supply Reliability, Dam and Reservoir Modifications, Facility Relocations, Adaptive Management (Reserving 378,000 acre-feet of Storage for Cold-Water Pool),Augment Spawning Gravel, Restore Riparian, Floodplain and Side Channel Habitat

CP5

Dam Raise - 18.5 feet
Increased Storage - 634,000 acre-feet

Focus and Components - Anadromous Fish Survival, Water Supply Reliability, Dam and Reservoir Modifications, Facility Relocations, Ecosystem Restoration, Construct Resident Fish Habitat at Shasta Lake & along Tributaries, Restore Riparian, Floodplain, & Side Channel Habitat and Increase Recreation Opportunities

No-Action Alternative (No Additional Federal Action)

Under the No-Action Alternative, the Federal Government would continue to implement reasonably foreseeable actions, but would not take additional actions toward implementing a plan to raise Shasta Dam

Method Used for Calculating Inundation Probability

Probabilities are based on frequency analysis of an 82-year Calsim model of Lake Shasta storage and are computed using the following general equation: p(x) = n / (m + 1). Where “p(x)” is the probability a user-defined water surface elevation will be equaled or exceeded in the selected month, “n” is the rank of a given Calsim elevation, and “m” is the total number of elevations for a given month over the simulation period.  All elevations reference North American Vertical Datum of 1988 (NAVD 88).

Note this analysis does not account for within-month variability of water surface elevation because Calsim provides a maximum resolution of one month based on monthly inflows. As a consequence, it is impossible to quantify the duration of inundation. Also note the probabilities do not account for other physically based factors that may influence water surface elevation such as wind waves.