[env-trinity] Trinity River water flows second highest since dams installed; release intended to flush waterway
tstokely at att.net
Fri May 6 07:52:44 PDT 2011
Trinity River water flows second highest since dams installed; release intended to flush waterway
By Dylan Darling
Redding Record Searchlight
Flows down the Trinity River Wednesday hit the second highest level since two dams were installed on the waterway 50 years ago.
The Bureau of Reclamation released 11,400 cubic feet of water per second from Lewiston Dam, and the flows should stay at that level until late Friday. The high water is being released to flush the river as part of an ongoing restoration, said Jennifer Faler, acting executive director for the Trinity River Restoration Program.
"We are at peak flow right now," she said Wednesday afternoon.
The bureau started regulating flows on the river in 1960 and the highest flow on record since then is 14,400 cfs in 1974, said Andreas Krause, a hydraulic engineer with the program, which is a collaboration of local, state and federal agencies. That year high water levels in Lewiston Lake threatened to damage Lewiston Dam, prompting the release.
The current heavy flows represent a departure from how the Trinity River used to be managed, Krause said. For decades after the river was dammed and diversions built to send its water to the Sacramento River, most of the water in Trinity and Lewiston lakes didn't go down the Trinity River.
Until 2005 about 90 percent of the river's water went to the Sacramento, Krause said. The trickle that was left hit a high flow of about 1,500 cfs about every year and a half.
Since the federal government finalized a restoration plan for the Trinity River six years ago the diversion to the Sacramento has decreased by half and the Trinity flows have increased, he said. Now they hit a high flow of about 6,000 cfs every year and a half.
Along the river restoration efforts include salmon spawning gravel deposits and riverside planting, Faler said. The current high flows will enhance these efforts, she said.
The rush of water will move the gravel and reshape the river, mimicking the ebb and flow of nature, Faler said.
"We want a dynamic channel," she said, "meaning that it changes each year."
While the flows are big now, the river used to see flows around 11,000 cfs every year and a half, Krause said.
"Before the dam this was a very common occurrence," he said.
And it's only a little less than a seventh of the peak recorded flow on the Trinity. The peak recorded flow at Lewiston was 71,600 cfs in 1955, Krause said.
The 11,000 cfs-plus flows are enough to keep rafters from running the river.
"For a while there are not going to be any of our boats on the water," said Marc Rowley, owner of Bigfoot Rafting Co. in Willow Creek.
He said some experienced kayakers might be tackling the white water though.
Flows around 5,500 cfs are considered "big," or high and fast, water on the Trinity River, said David Steinhauser, co-owner of Trinity River Rafting in Big Flat. Like Rowley, he said his company will keep its rafts out of the river until flows are down.
The temporary disruption in floating the river will be worth the results of the high water, Steinhauser said.
"I think it's going to make the upper sections of the river look more natural," he said.
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