Jason Sweet, Fish Biologist, Bonneville Power Administration: Spill has always been a very
important part of what we do, we’ve just progressed to a point now where we spill at
all eight dams on the lower Columbia and Snake rivers, 24 hours a day.
Mike Langeslay, Fisheries Biologist, U.S. Army Corps of Engineers: This new biological
opinion has survival performance standards. It’s 96 percent for spring migrating fish,
that would be yearly chinook and steelhead [salmon], and 93 percent for sub yearling
chinook. The studies we’ve done in the past few years show us being above that 96 percent
for yearly chinook and steelhead. And since we’ve made the improvements to the spillway
here we think we’re right there at the 93 percent for sub yearling chinook.
Jason Sweet: We have an extensive monitoring program that helps us tailor our spill program
to the needs of the fish. We’re constantly monitoring conditions in the river and fish
numbers in the river. And we mix transportation and the spill programs together to get the
optimal return of adults returning back to the system each year.
Mike Langeslay: You know, in the past decade we’ve really increased our knowledge on
how spill affects fish passage and how it’s related to the other parts of the dam.
Every dam is different because each spillway is different. Think of these three lower dams.
Bonneville: the spillway is kind of in its own channel. The Dalles: the spillway is at
a right degree angle to the powerhouse. And John Day: its one big long dam with the powerhouse
on one side and the spillway on the other.
You’ve got to look at the dam holistically and match your spill to what you’re trying
to do with the rest of the project. Look at fish passage through all routes and all how
your spill and powerhouse operation affects that.
Jason Sweet: So there’s this misconception out there that our program for fish doesn’t
include spill, which just isn’t true. We’re actually spilling 30 to 60 percent of the
river 24 hours a day from the beginning of April all the way through the end of August.
The vast majority of that time the biological opinion calls for exactly what the court has
ordered since 2005. As an example of this, the graph you that see now from Lower Granite
Dam in 2009, shows the court ordered spill as a solid black line. When we lay our BiOp
[biological opinion] spill on top of that with the yellow dashed line you can see the
only differences are in the middle of May and then again towards the end of August.
We’d like to shutoff spill for two weeks in May to maximize the number of fish that
we are able to put on barges and transport past the hydro system. Our science has shown
us that that is the opportune time where you get the most adults back compared to if you
had left them in river.
When you lay the fish passage graph on top of that, which is the solid blue line you
see now, you can see the reason why we shut off spill at the end of August is due to very
low fish passage numbers. By that period of the run, almost the entire population of fall
chinook has already passed the dams.
During the Snake River fall chinook migration, over one million juvenile fish heading down
stream passed Lower Granite dam on the way out to the ocean. Last June, the average number
of fish passing the dam each day was over 25,000. So by August if we’re only seeing
300 juvenile fish each day we can be pretty confident that the vast majority of the run
has passed. The actual date of when the trigger criteria have been met is going to vary from
year to year.
In the case when spill is shutoff on the Snake River, if fish numbers increase to over 500
fish for two days we will turn spill back on until the 300 fish trigger is met again.
And it’s also important to remember that the 300 fish spill curtailment trigger only
applies to the four Snake River dams. Spill continues through August 31 on the four lower
Columbia River dams in all cases, just like the court order.
In both places where we’re proposing something different than the court ordered spill, we
will consult with the region and look at the biological factors before we change the operation.
Prior to each spill season, we will look at our options for those two weeks in May, considering
new research to determine the best operation for fish.
Because of spill and structural improvements at the dams, juvenile fish survival through
all eight dams on the lower Snake and Columbia and rivers is as good as or better than it
was when there were only four federal dams on the Columbia River.
We worked with the states and tribes for more than two years to come to an agreement on
the spill program and we continue to work together to make improvements all the time.
So there really is broad agreement in the region that this is the best program for fish.
Mike Langeslay: Spill is a very important method of passing fish through our dams and
we’ve been working hard to make sure that we’re doing it the best we can. But more
spill isn’t always the answer, it’s really optimizing how you spill to get the safest,
best fish passage at your dam.
Jason Sweet: Sill provides a way to move fish safely and quickly. So we use it as one of
the cornerstones of our program in the 2008 BiOp. And that helps us, combined with the
other the hs: habitat improvements, harvest, hatchery practices; all of that combines together
to help us provide that package in the 2008 BiOp.