Dam manuals keep California’s water future in the past

“Sacramentans will recall how the operators of the Folsom Lake dam dumped billions of gallons of water last year at this time into the American River, never mind that the region was gripped by drought and a heat wave. The reservoir was down to 40 percent of capacity, under clear skies. But dam operators had no choice.”

The Oroville Dam crisis was about infrastructure. The scare this week stemmed from rickety spillways, not dam management.

But if other aspects seemed familiar, it may be because it again highlighted the gap between modern science and the antique flood-control manuals governing major dams in California. As The Bee’s Ryan Sabalow and Andy Furillo reported, the guiding document determining how full Lake Oroville can be in a rainy season hasn’t been updated since the Nixon administration, and is almost as old as the dam itself.

The U.S. Army Corps of Engineers manual, they reported, was last revised in 1970, two years after Oroville Dam’s completion. A lot can change in 47 years.

Science has advanced, in meteorology and engineering. Weather satellites, computer models and research into atmospheric rivers have made it possible to forecast storms with an accuracy previously unimagined. Climate change has upended assumptions.

Two of the biggest floods ever to hit the region have occurred since the Oroville Dam manual was written; on its sepia pages, it’s as if they never happened. The story is the same for all 54 of the state’s primary flood-control dams, whose manuals are 30 years old or older.

“California’s flood infrastructure is based on the hydrology of the past,” Jeffrey Mount of the Public Policy Institute of California told The Bee. “I don’t know a scientist anymore who thinks the future is going to look anything like the past.”

This isn’t just some clerical issue. The owners of those 54 dams cannot deviate from the manuals’ old models in determining water levels. That inflexibility has become a problem in both wet and dry years.

Sacramentans will recall how the operators of the Folsom Lake dam dumped billions of gallons of water last year at this time into the American River, never mind that the region was gripped by drought and a heat wave. The reservoir was down to 40 percent of capacity, under clear skies. But dam operators had no choice.

The installation of a new spillway at Folsom this year has triggered an update, finally, to its manual. Oroville’s problems, and ensuing repairs, could eventually mean a new and improved manual for it, too.

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