Вторник, 18 Мая, 2021

Oroville Lake Water Elevation Seen from Space

Eleena Tovar | 19 Февраля, 2017, 21:28

According to Saturday morning's official report, outflows from the lake continue to exceed inflows - meaning the lake level should still be dropping.

A California lawmaker wants to require more spillway inspections in the wake of evacuations prompted by damaged spillways at the country's tallest dam. A vast web of dams, reservoirs and canals stretches throughout California, delivering snowmelt from the Sierra Nevada Mountains up north to farmers in the Central Valley and cities in Southern California.

In fact, the Miramar Dam's spillway has never been used.

In a July 2006 memo to managers, first reported by The Mercury-News, a senior civil engineer with the agency's San Francisco office wrote that the agency determined dam safety "would not be compromised in the rare event of an emergency spillway discharge". "So if something happens inside the spillway that causes just a slight dislocation in there, that high-speed water will just start ripping it out".

Back when environmentalists and local officials were raising their concerns, the water resources department dismissed the need to fortify the hillside, insisting it would not be in danger if water cascaded down it.

Despite heavy rain and melting snow, engineers slowed releases later in the week after the hole grew.

Water is released from Lake Oroville Dam on Thursday after an evacuation order was lifted for communities downstream. As the San Jose Mercury News recently pointed out in a story, the same phenomenon almost caused the collapse of one of America's other largest dams, Glen Canyon, a 710-foot tall behemoth on the Colorado River, in 1983.

Authorities turned nearby highways into one-way roads south. Still, massive gridlock occurred.

A good example of the challenges associated with rapid evacuations of large areas and population centers include jammed gas stations with limited fuel supplies. Motels and hotels quickly sold out.

With less water flowing down the dam's spillway, officials hope to clear debris that threatens a hydroelectric power plant at the base of the dam.

DWR officials have said they're confident the reservoir will have enough empty space to withstand a major rainstorm expected to hit the region Monday and Tuesday.

Crews worked to dump thousands of tons of rocks to shore up the damaged spillways.

Despite ongoing spillway fix efforts and another round of storms forecasted to strike Northern California beginning Friday, officials have lifted mandatory evacuations and let residents back into the downstream communities of Oroville and Marysville. He conceded the evacuation was "chaotic" but defended the decision as "better safe than sorry". A water resources department spokesman said it was normal for maintenance crews to be troubleshooting cracks in the channel during dry summer months. "We're taking too much water out of the reservoir; it's too low", Orrock said.

The threat of a catastrophe at California's Oroville Dam appears to be over.

Despite the current inclement weather, work continues on the area below the spillway, the monoliths, access roads, and various eroded areas created by emergency spillway runoff.

The temporary fixes will last beyond snow melting this spring, and officials will then make long-term repairs, the water agency said.