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Seminar Speculates on Susitna Dam vs. Salmon

by Lorien Nettleton ~ November 11th, 2011

Potential impacts of the Susitna-Watana Hydroelectric dam were the topic at a Salmon Science forum on Thursday Afternoon in Wasilla. The Mat-Su Salmon Science and Conservation Symposium invited scientists, researchers and the general public to discuss all things related to the health and well-being of one of Alaska’s most valued fish in the Matanuska and Susitna drainages during the two-day conference.

At Thursday’s Susitna session, four presenters discussed their experiences and areas of research on the upper Susitna river, and talked about how changes to the flow rate of the river caused by the proposed Dam could impact salmon habitat. Plans for the Dam call for retaining large amounts of water in the summer and releasing it steadily through the winter in order to meet year-round energy needs. This change in the seasonal flow rates of the river could mean changing the salmon habitat on the 90 miles of the Susitna between Devil’s Canyon and where it joins the Chulitna.

Lifelong Talkeetna resident and river tour guide Israel Mahey spoke at the conference about his personal experiences and observations. Mahey, who was representing the Coalition for Susitna Dam Alternatives, said he runs the Susitna every day all summer long. Based on his personal observations, less water in the summer would dry out a lot of the sloughs completely. He also asked the group of scientists and conservationists what a change in water temperature caused by the dam would have on salmon life cycle, including whether it would change when salmon eggs hatch.

Jason Mouw from Alaska Department of Fish and Game gave a talk about the role frequent flooding plays in establishing new woody plant growth along the river. In his talk, Mouw showed how plant age studies along the flood plains were used to determine the role flooding played in the majority of new plant habitat formation. Much of what juvenile salmon eat, including bugs, is influenced by the presence of woody plants, he said.

Robyn BeeBee, a researcher for HDR, Alaska, Inc. and is one of many researchers contracted by the Alaska Energy Authority to study issues related to the Dam. Beebee has been studying the clearwater side-sloughs on the Susitna that provide the majority of salmon habitat. In her talk, said that the sloughs may be formed and maintained by flooding that happens during ice jams that come with high water flow during spring break up. With a change in water flow caused by the dam, she said the sloughs could be affected.

Jeff Davis, a contractor for Aquatic Restoration and Research Institute was the last presenter of the day. Davis has looked at ways changes in the sediment caused by the dam could affect the channel, saying it would likely degrade the main channel of the Susitna, which could reduce side sloughs and near-shore habitat. He also said less turbidity in the water could lead to improved habitat for juvenile salmon.

The Alaska Energy Authority says it plans to file the Preliminary Application Document for the Susitna-Watana Dam at the end of this year.

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