Increased spill at BPA dams would not be detrimental to fish – study

The fish conservation group Save Our wild Salmon (SOS) is advocating for increasing the amount of water spilled at Columbia River dams, saying the move would be beneficial to the river’s salmon while also making more transmission capacity available during times of high hydro and wind power supply.

“When [the Bonneville Power Administration (BPA)] decided to limit spill, citing salmon protection as its main argument in the wind debate, it really seemed contrary to all the science and analysis we had seen,” an SOS spokesperson told TransmissionHub on May 14.

The group cites its own research as well as the Comparative Survival Study, a study prepared for the Fish Passage Center and the U.S. Fish and Wildlife Service, as providing the evidence that supports their position.

“The Comparative Survival Study says even more spill than we saw [in 2011] would probably increase fish returns, so for Bonneville to be citing spill as its reason for needing to limit [spill]  … isn’t really a strong stance for them to be taking,” the spokesperson said.

“We did our own report last summer … and saw that the increased gas that was caused by spill in the river last year didn’t seem to cause any increased harm to the fish at all,” the spokesperson added.

Along with Pacific Coast Federation of Fishermen’s Associations (PCFFA), the Institute for Fisheries Resources (IFR), Idaho Rivers United (IRU), and American Rivers, SOS submitted a joint filing to FERC on March 27, protesting BPA’s oversupply management proposal.

“The salmon community has often called on the federal agencies to spill more water over the dams – not less – to help young salmon make their way safely to the ocean,” the groups said in their filing.

Those studies, however, have not convinced federal officials charged with protecting marine life. The regional administrator of NOAA’s National Marine Fisheries Service. William Stelle, restated his agency’s position on total dissolved gas (TDG) levels in an April 10 letter to BPA administrator Stephen Wright obtained by TransmissionHub.

“The best available science … indicates that spill levels resulting in TDG levels of [less than or equal to] 120% are generally safe for juvenile salmon and steelhead,” but that the incidence of gas bubble trauma increases “to nearly 3% at TDG levels of 121-125%, nearly 5% at TDG levels of 126-130[%], and over 6.5% at TDG levels greater than 130%.”

“TDG limits remain an important consideration in the provision of safe and effective passage for salmon and steelhead at the [mainstream] Columbia and Snake River dams,” Stelle’s letter concluded.

Fish advocates disagree. “There was so much water in the river last summer that there really wasn’t a way to control spill, so we actually saw total dissolved gas levels above than 120% range,” the SOS spokesperson said. “Even in the instance of [TDG] levels higher than 120%, we really saw minimal impact on the fish compared to fish transit [using] barges and trucks” to move the fish around Columbia River dams.

SOS and the other groups who joined the FERC filing contend the process of electricity generation is a greater threat than putting more water over spillways.

“Some juvenile mortality and injury is associated with all routes of dam passage, but turbines generally cause the highest direct mortality rates—generally ranging between 8% and 19%,” the groups said in their FERC filing. Citing 2005 NOAA technical memoranda, the groups added, “Juveniles passing through project spillways, sluiceways and other surface routes generally suffer the lowest direct mortality rates, typically losses are 2% or less.”

For now, though, the limitations on TDG remain the determining factor. EPA water quality criteria state that TDG concentrations should not exceed 110%. Waivers issued by the Washington Department of Ecology and the Oregon Department of Environmental Quality allow concentrations of 115% and 120% respectively.