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Use Water Now Or Later? Fish/Hydro Managers Make Flow Choices To Keep Salmon Moving Downstream
Posted on Friday, May 08, 2015 (PST)

The Technical Management Team, charged with the difficult task in a low water year of balancing spring juvenile fish passage with water and power needs in the region, dropped McNary flow objectives for the second week running and briefly raised flows from Dworshak Dam to help pass juvenile chinook salmon through lower Snake River dams.


Balancing available water to sustainable river flows, TMT again dropped spring flow expectations at McNary Dam for the second week in a row from 180,000 cubic feet per second to 170 kcfs at a special meeting, May 4.


Then, at its regularly-scheduled meeting May 6, it raised flows from Dworshak Dam on the  North Fork of  the Clearwater River from 5 kcfs to 9.7 kcfs (full powerhouse flows) in order to help struggling juvenile salmon pass through lower Snake River dams. The Dworshak increase will also help flows at McNary Dam.


As an additional aid to Snake River and Columbia River flows, the Bureau of Reclamation said May 7, that it would gradually increase flows out of its Milner Dam in the upper Snake River near Twin Falls, Idaho, to 2 kcfs by May 11 and maintain that flow through early June. The upper Snake River reservoirs are at 83 percent of storage capacity.


BOR says it is taking this action to provide additional water for salmon migration lower in the rivers “in accordance with NOAA Fisheries 2008 Upper Snake Biological Opinion.”


Faced with one of the worst water supply forecasts in the past 55 years, TMT lowered the flow objective at McNary Dam from 220 kcfs to 180 kcfs on May 1, hoping that flow level would be enough to help juvenile salmon pass the dam and other Columbia River dams downstream.


Average flows at McNary the week of April 27 were at 160 kcfs, so to reach the 180 target set by TMT on May 1 required dam operators to increase their draft of the Grand Coulee reservoir.


By Monday, May 4, it had become apparent to the managers that Coulee was drafting at a much faster pace than they had anticipated, risking the chance that Lake Roosevelt, the dam’s reservoir, would not refill by early summer.


“The inflow at Coulee is running about 85,000 cubic feet per second and the Snake River is done with runoff,” said Tony Norris of the Bonneville Power Administration. “None of that adds up to 180 kcfs at McNary Dam.”


The 85 kcfs inflow includes about 10 kcfs that will be pumped into Banks Lake to be used for irrigation, so the Coulee inflow is really closer to 95 kcfs, he added, but the Banks Lake allotment is not available to augment flows downstream.


Passing inflows through Coulee, Norris said, gives McNary about 160 kcfs to 165 kcfs. “What we are doing now will use up at least one-half foot per day,” he warned, speaking of the 180 kcfs target.


Given the situation, TMT on Monday further reduced average flows at McNary to 170 kcfs and, by Wednesday this week, flows were averaging 165 kcfs to 170 kcfs, according to Mary Mellema of the BOR, which operates Grand Coulee Dam.


She said flows will continue at this level as long as the Coulee reservoir does not fall below an elevation of 1,243 feet. An elevation below that would cause difficulties in refilling the reservoir and that’s water that will be needed throughout the summer. The reservoir elevation on Monday was 1,249.1 feet, she said, but “by the end of Wednesday it would be at 1,247 feet, with only four feet to play with,” if outflows continued at 180 cfs. Refill begins after May 13.


The federal biological opinion for Columbia/Snake salmon and steelhead includes a flow objective at McNary Dam of 220 kcfs to 260 kcfs during the spring juvenile salmon migration season, which is achievable during most years. However, in low water years, the BiOp allows for flexibility in managing the situation.


For more information, see CBB, May 1, 2015, “As Water Supply Expectations Lower So Do Flow Targets At McNary Dam During Juvenile Salmon Migration,”


The current flows of 165 kcfs to 170 kcfs at McNary seems to be working for juvenile salmon as they are passing down through the Columbia River at an expected rate, according to Paul Wagner, NOAA Fisheries, at TMT’s May 6 meeting.


However, passage of juveniles on the Snake River are below expectations and some steelhead juveniles are likely being waylaid in the Lower Granite reservoir, Wagner said as he pushed for increasing flows from Dworshak Dam on the Clearwater River, upstream of Lower Granite Dam.


Steve Hall of the U.S. Army Corps of Engineers, which operates the project, warned that using Dworshak  water now could jeopardize refilling the reservoir by the end of June.  In fact, given the changing water supply forecast in the area, he said it would be more prudent to aim to refill the reservoir in early June.


Runoff volume April 1 was 70 percent of normal and that dropped to 54 percent of normal by May 1, he said.


“The difference is the weather,” Hall said. “It’s a relatively cool protracted melt and that doesn’t translate into runoff. The forecast is for 10 kcfs inflow, but it more likely will peak at 8 to 8.5 kcfs.”


Water from Dworshak can be used in the mid-summer months of July and August to cool flows at lower Snake River dams.


“What’s more important, refill or flow augmentation at this point in time?” he asked.


TMT’s salmon managers chose a short period of flow augmentation to try to move more juvenile salmon through the lower Snake River, asking for four days of full powerhouse flow, which is about 9.5 kcfs, going to 5 kcfs Saturday and down to 1.6 kcfs Sunday, where flows will stay while the reservoir refills.


“None of this is where people want to go and we acknowledge the significant risks this operation has on refill,” Wagner said, speaking for salmon managers at the May 6, TMT meeting. “But we think the benefits to the spring fish will outweigh the temperature benefit later on.


“We’re going into this with eyes wide open,” he added. “But the water we could potentially use in August, we’ll use now for these smolts.”


TMT will continue to consider both the McNary and the Dworshak decisions again at its meeting, May 13.


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