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Why aren’t we building more dams?

Published: Wednesday, Feb. 12, 2014 - 12:00 am

Q: Why aren’t we building more dams to store more water, instead of wasting money on a bullet train? – David LaChance, Oroville

A: First, a little history. There are thousands of dams in California, and most of the “good” dam sites have already been taken. There are not a lot of places left with a narrow slot canyon downstream of a large watershed. Most of the locations that remain require very large, expensive dams that would not yield a lot of water. This makes the economics iffy.

In the 1990s, the now-defunct CalFed Bay Delta Program undertook a detailed study to search for the best remaining dam sites across the state. It weighed topography, water yield, cost, environmental risks and other factors. Four emerged as the most promising, and are now in various stages of final study:

• Sites Reservoir in Colusa County, an “off-stream” reservoir filled from a canal diverting Sacramento River water. Water yield: 470,000 to 640,000 acre-feet. Cost: $2 billion to 3 billion.

• Temperance Flat Reservoir, on the San Joaquin River east of Fresno. Water yield: 400,000 acre-feet. Cost: $1 billion to $1.4 billion.

• Raise Shasta Dam on the Sacramento River. Water yield: 265,000 to 634,000 acre-feet. Cost: $900 million to $1.2 billion.

• Raise Los Vaqueros Dam in Contra Costa County. Water yield: 115,000 acre-feet. Cost: $500 million.

Another proposal recently emerged to expand San Luis Reservoir near Los Banos. The dam needs to be strengthened to withstand earthquakes. State and federal officials are considering raising the dam 20 feet at the same time to create capacity for an additional 130,000 acre-feet of water. Cost: $360 million.

Once the studies are done, the next challenge is paying for these projects. That will require an act of Congress, a state bond measure, local tax increases, or all those things.

Submit your question for The Sacramento Bee’s water team.

Call The Bee’s Matt Weiser at (916) 321-1264. Follow him on Twitter @matt_weiser.

Read more articles by Matt Weiser

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