Anderson Reservoir spills over for first time in 11 years as storms slam Bay Area

SF Gate

A roaring waterfall is pouring over Santa Clara County’s Anderson Reservoir for the first time in 11 years.

The town of Morgan Hill, Calif. now has its own Niagara Falls–like attraction, and over the weekend many came out to take photographs and videos of the spectacular surge.

The man-made lake reached full capacity and began cascading over the spillway and into Coyote Creek on Saturday, the latest dramatic event to unfold amid a relentless rainy season.  

The lower spillway waterfall at Anderson Dam in Morgan Hill, Calif., on Monday, Feb. 20, 2017. Photo: Len Ramirez / KPIX 5Flooding along Coyote Creek is expected on Tuesday as the reservoir continues to spill over.

“The update for today is that we are seeing quite a large flow of water from the current storms,” said Marty Grimes, a spokesperson for Santa Clara County Water District. “It hasn’t peaked yet. It will certainly spill all day today and could continue all week, depending on how much rain comes from the next storm. We expect flooding on Coyote Creek later today in a few low spots.”

Unlike Lake Oroville’s eroded spillway farther north, this reservoir’s spillway isn’t damaged and is functioning properly. But there’s still concern. The dam isn’t seismically sound, and when the lake is above 68 percent capacity, it could fail in a 7.25 or larger earthquake.

To avoid a catastrophic flood, state agencies require Santa Clara Valley Water District to keep the lake level 45 feet below the dam crest, with the understanding that this might not be possible in extreme conditions.

This winter of back-to-back storms can certainly be considered extreme. In an attempt to keep the reservoir level down, the water district has been releasing water through an outlet at the bottom of the dam since Jan. 9, at a rate of more than 400 cubic feet per second. But the rate of flow into the reservoir has often exceeded the rate of water being released this winter, according to a report from the water district. The water level in the reservoir reached its crest on Feb. 18.

Anderson is the largest of the district’s 10 reservoirs and is a primary water source for the county. The reservoir has reached full capacity 10 times since it was built in 1950, most recently in 2006.

http://www.sfgate.com/bayarea/article/Anderson-Reservoir-Dam-spilling-waterfall-spillway-10947314.php

2 thoughts on “Anderson Reservoir spills over for first time in 11 years as storms slam Bay Area

Join the Conversation

Your email address will not be published. Required fields are marked *


*