More Reservoirs

It seems like a no-brainer, but this article brings up some points as to why California might not want to pay to increase its water storage capacity:

But this year, as California faces long-term supply shortages, some water policy experts are raising deeper questions: Is there enough water left in California to justify the cost of dams? If taxpayers do front some money, what are they really buying? Are they propping up a project with shaky economics, or buying something with real public value?...

“There is no realistic solution to California’s diverse and ever-increasing water needs that does not rely heavily on additional storage,” state Sen. Cathleen Galgiani, D-Stockton, said in introducing her bill. It is the most ambitious, offering $6.2 billion to four new reservoir projects. “Although our population has nearly doubled over the past few decades, we have not significantly increased our water storage capacity.”

Despite this enthusiasm, some experts now question the notion that more reservoirs are the answer to water scarcity. One reason is that most of the good dam sites in California are already occupied by thousands of existing reservoirs.

The remaining sites would require much larger dams. This drives up construction costs – as well as the cost of the water ultimately delivered.

More importantly, most of the available natural runoff in California already has been claimed. The State Water Resources Control Board estimated in 2008 that it already has allocated eight times more water rights in the Sacramento-San Joaquin Delta watershed, the state’s largest, than the watershed produces in natural runoff in an average year.

“I think we’re seeing definite diminishing returns on investments in storage,” said Jay Lund, director of the Center for Watershed Sciences at UC Davis and a professor of civil and environmental engineering...

The five reservoirs would have a combined capacity of about 4 million acre-feet of water, which sounds like a lot. But, together, the five projects would yield “new” water supply of about 400,000 acre-feet in an average water year for farms and cities, or just 10 percent of their total capacity, according to a Bee analysis of project data. That’s less than half the total storage of Folsom Reservoir alone. In a dry year, the combined yield would increase slightly, to about 520,000 acre-feet. One acre-foot is enough to meet the needs of two average California households for a year.

By comparison, existing reservoirs in the federal government’s Central Valley Project – including Shasta, Trinity and Folsom – are able to deliver about half of their total capacity to farms and cities.

The projected water yield from the new reservoirs is relatively low because most of the water they are capable of storing already belongs to someone else or is obligated to fishery protection. The reservoirs would be required to pass this water through at the appointed time rather than selling it as a “new” supply...

There's a lot more there, very interesting.