Bakersfield residents should see more water than usual tumbling and crashing over rocks and boulders in the Kern River Canyon this summer. 

No, nothing like record amounts, but more water than one would typically see in a year like this one, a year with just half the normal snowpack runoff in the Kern River Basin.

"They're releasing water at the dam to lower the lake level," said Matt Volpert, owner of Kern River Outfitters, a rafting company based in Wofford Heights.

Volpert is right. Although water in various amounts is constantly being released from Isabella Lake into the lower Kern River, this year something different is happening.

Water managers are being instructed by the U.S. Army Corps of Engineers to reduce the "storage pool" of the reservoir to a level that will allow heavy construction to take place on the upstream side of the Auxiliary Dam.

According to Kern River Water Master Dana Munn, in most years, the reservoir is drawn down to 170,000 acre-feet by Nov. 1 each year and maintained at or below that level until Feb. 1 when snowmelt runoff predictions become available. This seasonal drawdown prepares the lake for rain and the expected spring snowmelt.

The water that remains in the lake during this three-month period is called "winter carryover."

There have been occasional exceptions made for more winter carryover, Munn said. But under no circumstances has it been allowed to exceed 245,000 acre-feet.

This year, things are different.

Years of heavy construction work are about to begin on the Corps of Engineers Isabella Dam Safety Modification Project, and the planned work will require the lake level be reduced to a fraction of normal winter carryover by Oct. 1, he said.

How small a fraction?

According to a letter sent to Munn from Joe Forbis, water management section chief in the Corps' Sacramento District, the "storage pool" must be lowered to 71,441 acre-feet, 58 percent less than the normal winter carryover.

The Army Corps has awarded this latest construction contract to the Flatiron-Dragados-Sukut Joint Venture. The work will include modifications to the Main and Auxiliary dams, modifications to the service spillway and construction of an emergency spillway.

"These modifications are necessary to address several project dam safety deficiencies with the primary objective of protecting the public," Forbis said in the letter.

The Corps expects to acquire the Borel Canal easement from Southern California Edison, which is required by the Corps prior to exercising a contract option for the work on the Auxiliary Dam.

If all goes as expected, contractors will seal the Borel conduit and canal that pass through the Auxiliary Dam. To accomplish this, Forbis said, pool storage is expected be lowered for a four- to six-month period, which could keep the lake level low until April 1, the end of the rain and snow season.

But Munn doubts the Corps will need the full six months.

"Yes, they could take that long as that would fit their prior environmental documents," he said in an email. "But on a practical construction basis it should not take that long for the specific needed work. They have verbally estimated, without any commitment, that they need two and a half months."

There's little doubt that this one-time reduction in winter carryover storage means less flexibility for agricultural and urban water interests downstream.

"Normally, folks would be tucking water away to use it next year," Munn said.

The dam needs to be fixed, he said. It's better to reduce the winter carryover in a low water year than a barn burner year. So, this is as good a year as any to begin the big construction projects.

On a 50-percent year, the winter carryover would probably only have reached 130,000 acre-feet anyway, he said.

No water is going to waste. Summer is peak irrigation time, and growers in the valley require water for thirsty crops.

It appears Munn will have little trouble meeting the Oct. 1 deadline. In just the past week, the lake level has fallen from 223,819 acre-feet to 211,152 acre-feet, a drop of some 12,600 AF. The water master still has 13 weeks to drop the level by another 140,000 AF.

Meanwhile, Bakersfield residents may see more water in the river than usual in a 50-percent year. But just like any other summer, canals and aqueducts will reroute most of it to farms and fields before city residents lay eyes on it.

The river in the canyon, however, is another story. It's a raging beauty.

Steven Mayer can be reached at 661-395-7353. Follow him on Facebook and on Twitter: @semayerTBC.

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