Impacts on Lake Powell from "Grand flushes"?
Federal officials recently announced "flush" flows from Glen Canyon Dam into the Colorado River to restore natural sediment-moving events in the ecosystem. Here is the Trib's story. I wondered how those releases might impact sport fish and fishing on Lake Powell. I sent an email to Wayne Gustaveson, Lake Powell Project Leader for the Utah Division of Wildlife Resources. Here's his response.
"Sediment floods released from Glen Canyon Dam will not necessarily increase the amount of water sent downstream from Lake Powell. Timing of water releases will be altered, but total volume may be the same within the water year and amount of precipitation received.""BOR manages the water level of Lake Powell and can release more at one time followed by reduced flows later on. At the end of the water year the required 8.23 MAF will flow downstream so the flush is of little concern to annual lake level. The large overall release last year to bring Lake Mead water levels up is being mediated this spring by holding Lake Powell at a stationary level despite the absence of any sizable runoff. When I checked inflow and outflow this morning I found that water coming in was exactly the same as water going out. (928-645-3978 for recorded message).""The details of the previous flood events show a benefit to Lake Powell fisheries from spring flood events. A rapid drawdown (as much as 3 feet in 3 days) of Lake Powell prior to spring warming draws sediment toward the main channel. Extra nutrients are released as the sediment moves resulting in an unexpected increase in plankton and then shad forage, which translates into an increase in fish health for all game species in the lake.""I am not qualified to discuss how successful these flushing floods are at moving sediment in the river or how endangered fish respond to flood events. But for the benefit of Lake Powell I would hope that any floods would be performed in the springtime instead of fall. That way, lake fisheries will benefit from the flood event."
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