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NW Fishletter #369, May 1, 2017

[4] Agencies and Tribe Recommend Operational Changes at Montana Dams

Operational changes at Libby and Hungry Horse dams would increase their value to the region, according to a report released last month by Montana Fish, Wildlife & Parks and the Northwest Power and Conservation Council, in consultation with the Confederated Salish and Kootenai Tribes.

The report, "Montana Operations at Libby and Hungry Horse Dams," describes the dams' current operations and details recommendations for the two hydro projects.

Located in northwestern Montana, Libby Dam stores water that runs through 17 downstream dams, while the Hungry Horse Dam stores water for 20 downstream dams (including ones in Canada). Together the two Montana projects hold 40 percent of U.S. water storage in the Columbia River Basin.

Hungry Horse coordinates its operations with Seéliš Ksanka Ql'ispé Dam (formerly Kerr Dam), located at the mouth of Flathead Lake and owned by the Confederated Salish and Kootenai Tribes.

Future operational changes at these dams--and at 14 other federal multipurpose dams in the Columbia Basin--could result from the pending new FCRPS BiOp and Environmental Impact Statement and from revisions to the U.S.-Canada Columbia River Treaty.

"Upcoming negotiations will likely expand on previous efforts to minimize harm to the ecosystem while ensuring the benefits from the dams," the report says.

Sturgeon benefit from a pulse of water flow in spring. Credit: T. Grover/NWPCC

Since the 1990s, operational adjustments at the dams have attempted, with some success, to reduce impacts on fish and the ecosystem. However, the paper said, more needs to be done to meet ESA and Northwest Power Act obligations.

"Dam operations continue to change the magnitude and seasonality of the hydraulic cycles and so fail to achieve full ecological functionality, particularly associated with the riparian community," it said.

Improvements include adjustments in VarQ, or variable discharge, which allows more water to stay in reservoirs in late winter than under standard flood-risk management.

First implemented in the early 2000s at Libby and Hungry Horse dams, VarQ creates more natural conditions for ESA-listed bull trout, ESA-listed Kootenai white sturgeon and other native fishes without compromising flood-management requirements.

Lower winter flows are recommended to encourage survival of riparian plant communities established during summer operations, particularly during high-water years, but subsequently destroyed by high-winter flows. Riparian vegetation supports both aquatic and terrestrial species.

Improving reservoir refill during dry years would also help meet reservoir storage criteria and biological constraints in the Confederated Salish and Kootenai Tribes-Montana Water Compact.

Sliding-scale or modified rule curves similar to VarQ should be considered at other reservoirs in the Columbia Basin, the paper said.

Montana also recommends assessing potential modifications to current flood-risk operations "including evaluating all cost-effective actions to manage high flow events especially in the lower basin, including reconnecting floodplains." This is proposed in the 2013 U.S. Entity's Regional Recommendation for modernizing the Columbia River Treaty.

"Any changes in flood control management arising from this process could reduce the current flood management demands on Libby and Hungry Horse dams, with corresponding benefits to headwater reservoir operations and downriver ecosystems," the paper said. -Laura Berg

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Publisher/Editor-in-Chief: Mark Ohrenschall, Editor: Laura Berg
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