High river flows in the Snake and Columbia
rivers and resulting involuntary levels of spill over dams are rendering moot court-ordered
spring spill to state-mandated caps on total dissolved gas.
Recent warm weather is melting snow and
causing high water in most of the Columbia and Snake river basins. River flow
at McNary Dam Wednesday hit 490,000 cubic feet per second and the Columbia
River level at Vancouver hit flood stage at 16 feet early Thursday morning.
A three-judge panel of the Ninth Circuit Court
of Appeals ruled April 2 in favor of an April 2017 U.S. District Court
injunction allowing more spring spill at four lower Snake and four lower
Columbia river dams. With the decision, spill to the gas cap began April 3 at
lower Snake River dams and at lower Columbia River dams April 10. The
additional spill through June 15 is designed to aid migrating juvenile salmon
However, so far this month the court order is
largely moot as high flows are causing high involuntary spill at all lower Snake
and Columbia river dams.
TDG May 10 and 11 exceeded the gas cap set by
Oregon and Washington at Lower Granite Dam, hitting 121 percent TDG in the
dam’s tailrace (the tailrace gas cap is 120 percent). However, the Corps is
finding it difficult to keep the TDG in the Little Goose Dam forebay (the dam
immediately downstream of Lower Granite) at or below the 115 percent forebay
gas cap when actual spill exceeds the target spill of 31 – 33 kcfs. Spill was
as high as 51 kcfs May 11. As a result, the forebay TDG limit at Little Goose
has been exceeded five times this month, Dan Turner of the Corps’ River Control
Center told the interagency Technical Management Team at its meeting Wednesday,
Turner said flows have dropped at Lower
Granite the past few days but are expected to rise again late this week. He
expects involuntary spill at the dam to continue through at least May 29.
Target spill at Little Goose Dam is 28 – 30
kcfs, but the dam spilled 65 kcfs on May 11. That involuntary spill has
resulted in gas cap exceedances five times in the tailrace, but nearly every
day in the downstream forebay at Lower Monumental Dam.
Lower Monumental target spill since May 1 has
been 27 – 31 kcfs, but the target has been exceeded six times and the
downstream forebay TDG at Ice Harbor Dam has been exceeded every day this
Spill was as high as 105 kcfs at Ice Harbor
Dam this month, while the target was just 80 kcfs, causing TDG exceedances on
seven days this month.
TDG hit 134 percent in the tailwater of McNary
Dam May 15 and 16, exceeding the state gas cap by 14 percentage points. Spill
on those days was 370 kcfs and 362 kcfs respectively, while the target was far
lower at 145 kcfs. McNary has exceeded the spill cap in its tailwater nearly
every day this month. Downstream in the John Day Dam forebay TDG has been
higher than the 115 percent cap since May 5, hitting 131 percent May 15.
Target spill at John Day is 90 kcfs, but
actual spill has exceeded that level every day this month, hitting a high of
275 kcfs May 16. That produced a TDG of 143 percent. Downstream at The Dalles
Dam forebay TDG has exceeded the 115 percent cap since May 5 with a high of 130
percent May 15.
Target spill at The Dalles is 90 kcfs, but
that has been exceeded every day this month, with a high of 301 kcfs May 13,
producing TDG in the tailwater of 127 percent. Downstream in Bonneville Dam’s
forebay, TDG has exceeded 115 percent all month, with a high of 128 percent on
three days, May 13 – 15.
Turner expects involuntary spill at The Dalles
to continue into mid-June before river flows decline into August.
TDG in the Bonneville tailrace hit 128 percent
May 13. Target spill is 121 kcfs, but actual spill has been as high as 311
A result of high spill levels at dams is gas
bubble trauma found in some juveniles. Some 17 percent of chinook and steelhead
sampled at Bonneville Dam had signs of GBT May 15, but just 1 percent to 2
percent showed GBT signs at Little Goose, Lower Monumental and McNary dams. See
For information about lower Snake River dams,
see http://pweb.crohms.org/ftppub/water_quality/12hr/snake_river.html. For information on lower Columbia River dams, see http://pweb.crohms.org/ftppub/water_quality/12hr/columbia.html
McNary and John Day dams are currently
carrying reserves of 25 megawatts each, meaning that water that would produce
that much power at each dam is either held or spilled until the region needs
“We can either run that water through the turbine
or spill it,” Tony Norris of the Bonneville Power Administration told TMT. “It
is a tool we could use to lower TDG,” although holding reserves is only
deployed about 5 percent of the time.
Taking Norris up on his offer, salmon managers
at TMT requested that BPA and the Corps run that water through turbines rather
than over spillways as a way to control TDG. The request will continue through
Friday, May 25 and will be revisited at TMT’s next meeting May 23.
BPA has said the additional spring spill to
gas cap levels will cost the power system as much as $40 million in lost
revenue this year because the water will be spilled and not used for
--CBB, May 4, 2018, “Maintaining Court-Ordered
Spill At Columbia/Snake Dams Without Exceeding Gas Caps Proves Challenging,” http://www.cbbulletin.com/440650.aspx
--CBB, April 13, 2018, “Court Ordered Spring
Spill For Fish Begins On Four Lower Columbia River Dams,” http://www.cbbulletin.com/440516.aspx
-- CBB, April 6, 2018, “Appeals Court Rules In
Favor Of More Spill For Juvenile Salmon, Steelhead At Columbia/Snake Dams” http://www.cbbulletin.com/440480.aspx
--CBB, April 6, 2018, “New Court-Ordered Spill
Regime Based On Dissolved Gas Caps Begins This Week,” http://www.cbbulletin.com/440479.aspx
--CBB, March 23, 2018, “Ninth Circuit Hears
Arguments On More Spill For Juvenile Salmon/Steelhead At Columbia/Snake Dams,” http://www.cbbulletin.com/440399.aspx
- CBB, December 8, 2017, “Briefs Filed In
Appeals Court To Expedite Challenge To Increased Spill For Juvenile Salmon,