Some facts on water storage that could be added in California.
If Shasta Dam was built to its originally engineered height its water storage would triple, from the current 4,552,000 acre feet to 13,890,000 acre feet , as Wikipedia notes:
Reclamation has suggested three options for the dam raise, ranging from less than 20 feet (6.1 m) to more than 200 feet (61 m). The “low option”, which simply comprises adding a vertical concrete dike to the top of the dam, would provide maximum additional storage while minimizing requirements for reconstruction of buildings and facilities around Shasta Lake. The “intermediate option” would require adding more than 100 feet (30 m) to the crest and replacing the elevator towers on the front of the dam, and the Pit River Bridge and small towns around the lake, if not modified or moved, would be inundated. Finally, the “high option” would raise the dam over 200 feet (61 m), tripling the volume and doubling the surface area of the reservoir. Both the intermediate and high options would require saddle dams constructed at key points along the lake to keep it from overflowing.
Retrieved April 14, 2015 from http://en.wikipedia.org/wiki/Shasta_Dam
If Auburn Dam was built it would provide additional water storage of 2,300,000 acre feet , as Wikipedia notes:
In recent decades, California has been struck with a series of severe droughts. In order to facilitate continued deliveries of water to the thirsty southern half of the state, the Central Valley and State Water Projects have been forced to cut water supplies for agriculture in much of the San Joaquin Valley. Annual deficits of water in the state are projected to rise from 1,600,000 acre feet (2,000,000 dam3) in 1998 to an estimated 2,900,000 acre feet (3,600,000 dam3) by 2025. The state has proposed three or four solutions to the shortfall. One, the Peripheral Canal, would facilitate water flow from the water-rich north to the dry south, but has never been built due to environmental concerns. The raising of Shasta Dam on the Sacramento or New Melones Dam on the Stanislaus, or the building of Sites Reservoir, has also been proposed. Lastly, the Auburn Dam has also been revived in light of this. According to supporters, it would cause the least environmental destruction of the multitude of choices, and would give the most reliable water yield, regardless of its skyrocketing costs.
Retrieved April 14, 2015 from http://en.wikipedia.org/wiki/Auburn_Dam