Zero-Flow Scenario Debated
by Bill Rudolph
Columbia Basin salmon managers were uncomfortable enough with the Bonneville Power Administration's proposed winter operations for lower Snake dams that they tried to keep them from being implemented.
The proposal is nothing new, said Scott Bettin, who represents BPA at the Technical Management Team, a weekly forum of hydro and fish managers. He said it's a typical December-through-February operation that has been in effect for many years.
BPA wanted to generate more power at the four dams on the lower Snake during daylight hours, when prices are better for selling power than during the evening hours. BPA would rather shut the powerhouses down altogether at night and go to "zero flow" in the river.
Bettin said the operation could increase revenues by about $25,000 a day because it would allow the sale of about 310 additional megawatts during the heavier load daytime hours.
The zero-flow operation has been in effect since 1987, when the Corps of Engineers reached an agreement with fish managers to allow such operations at night and on weekends during winter months.
But when Bettin brought the issue up Dec. 1, after the Corps suggested more "regional coordination," some fish managers wondered about possible adverse effects from the zero-flow option. Flows in the lower Snake are already extremely low, running below 20 kcfs, less than the 10-year average for this time of year.
The fish managers said small numbers of steelhead are still migrating upriver. They were also concerned that redds dug by fall chinook in tailraces below the dams might be de-watered by the zero-flow operation, although no redd counts were available during the discussion.
Partial surveys conducted from 1993 to 1997, after some salmon eggs were found during dredging operations, turned up few redds. Researchers found 14 redds below Lower Granite Dam in 1993 and five redds the following year, but no redds were observed there the last two years of the study.
Four redds were found behind Little Goose Dam in three of the four years, but only one was counted in 1997. In the last two years of the study, the redd counts (up to five) accounted for less than 5 percent of all the fall chinook redds in the Snake River.
Most falls spawn in the mainstem far above Lower Granite Dam. In 1997, about 200 redds were counted above the dam in the Snake and tributary rivers.
Since then, the Corps of Engineers has required no additional surveys of the lower Snake spawning areas, Battelle researcher Dennis Dauble told NW Fishletter. He said it would be interesting to see if the large numbers of fall chinook returning in the past several years have contributed to more redds in the lower Snake corridor. According to a recent BPA-funded report, 1,854 fall chinook redds were counted above the dam in 2002.
WDFW biologist Glen Mendel said he didn't see how the zero-flow operation would adversely affect redds, since river elevations barely change from day to night.
"There are still a few steelhead going by," he said, "but they're in no big hurry."
Mendel's greatest concern, rather, was coordinating fish ladder maintenance with the zero-flow operations. He pointed out that when a fish ladder is closed for maintenance, it's de-watered anyway, hence unavailable for migrating fish.
The zero-operations issue came up at the Dec. 4 Implementation Team meeting, but it was not officially raised to a decision-making level by policy managers. It was kicked back to the TMT for more jawboning, but the operation began that night. At the Dec. 17 TMT meeting, fish managers still had not presented any updated information.
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