The Swanson River: a treasure worth keeping

Posted: Friday, May 07, 2010

The Webster dictionary defines a treasure as "something of great worth or value." I suspect that in most people's eyes, the Swanson River and its watershed falls in this category.

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J. Morton, Usfws
J. Morton, Usfws
View of the Swanson River in early fall from the bridge that crosses into the Swanson oil & gas field

With an average gradient of 4 feet per mile, the Swanson River flows lazily for most of its 48 miles through the Kenai National Wildlife Refuge. Its watershed drains 280 square miles of forest and muskeg in the Kenai Lowlands, and includes over 125 named lakes (see map).

The Swanson River and its tributaries have significant runs of coho (more than 20,000!) and sockeye salmon and world-class rainbow trout fisheries. Dolly Varden and other native fishes like sticklebacks, suckers, whitefish, and slimy sculpins also inhabit in the river.

Daniel Quick, author of Kenai Canoe Trails, calls the uppermost reaches of the Swanson River "difficult passage." With that in mind, the watershed starts arguably at King Lake, and the headwaters of the river arguably flow from Wild Lake -- it's a little difficult to be certain. The river flows through the Swanson River Canoe System, one of the two National Recreational Trails and part of the 1.3 million acres of Congressionally-designated Wilderness on the refuge.

From here it flows northwest briefly before bending towards the southwest past abundant beaver lodges, and aspen and birch regenerated in the aftermath of almost 400,000 acres that burned in 1947 and 1969. It flows through some of the best coho spawning habitat on the peninsula, and spectacular jump shooting for waterfowl.

About 19 miles down from Gene Lake, it passes the Swanson Landing where lots of kids (mine included) have whiled away the hours catching panfish-size rainbows that seemingly never learn to avoid fish hooks. It flows under two grated, steel bridges (see photo) connecting the 8,000 acres (currently leased to Chevron) that surround the 1957 Discovery Well which helped put Alaska on the road to statehood. It flows past traditional campsites that families have used for decades to hunt moose.

And for all but the last mile or two, it remains within the refuge boundary. Only as it approaches the Cook Inlet does it flow under one more paved bridge in Captain Cook State Park.

But despite being surrounded by public lands managed by Federal and State agencies, the Swanson is an imperiled treasure. Reed canary grass and northern pike, both invasive non-native species, threaten this otherwise pristine river.

In the Lower 48, reed canary grass (Phalaris arundinacea) can dominate the shorelines of lakes, rivers, and wetlands. The rhizomes and dead stems and leaves of this grass can form a sod layer over 1.5 feet thick, choking out most native plants. When reed canary grass encroaches into active channels, as it has in the Pacific Northwest and Great Plains, it accelerates siltation, reduces the active channel area, and alters the hydrology. In slow-flowing rivers like the Platte River in Nebraska, reed canary grass has totally filled the channel and cost millions of dollars in dredging to re-open the channel.

Reed canary grass is not believed to be native to Alaska. It was introduced to southeast and southcentral Alaska as forage and for bank and roadside stabilization. On the Kenai Peninsula, this grass has spread to more than 260 populations including several extensive colonies within the roads, pads and other commercial infrastructure within the Swanson oil and gas field. We have found reed canary grass growing within 100 feet of the river. Without some kind of interdiction, it's clear that reed canary grass will spread to the Swanson River. The only question is how much damage will it do?

Meanwhile, at the mouth of the Swanson River, a population of northern pike (Esox lucius) inhabits Stormy Lake, a body of water that straddles the refuge boundary and drains into the Swanson River near its mouth. The outlet is an unnamed stream, beginning at the northern most point of the lake, and flows into the Swanson River less than a mile from Cook Inlet.

The northern pike is not native to the Kenai, and it threatens populations of our native salmonids that have evolved in the absence of the predatory pike. Northern pike were likely introduced (illegally) to Stormy Lake about three decades ago.

The lake historically supported rainbow trout, arctic char and coho, but now pike up to 20 pounds are caught in the lake. Since 2001, the Alaska Department of Fish and Game has maintained a fyke net at the lake outlet to prevent pike from reaching the Swanson River, and local fish biologists believe that the Swanson River is still pike-free.

But like reed canary grass, poised just beyond the banks of the Swanson River, this is an accident waiting to happen.

The net is a temporary obstacle that can be easily breached or damaged by high water, gnawing wildlife or vandalism.

Not to sound too pessimistic, but one plausible future scenario for the Swanson River is a grass-filled ditch with pike, few coho or rainbow, and not even enough open water to paddle your canoe in!

We're not quite ready to throw in the towel. Actually, far from it. With some matching funds from Chevron, the refuge started treating reed canary grass last summer in the oil and gas field with glyphosate, an herbicide with very low toxicity to non-target wildlife.

Meanwhile, an interagency group is exploring chemical and structural solutions to eradicating pike in Stormy Lake. With a little persistence and a lot of luck, the Swanson River will remain the treasure that all of us enjoy.

John Morton is the Supervisory Fish and Wildlife Biologist at the Kenai National Wildlife Refuge. He is also adjunct faculty at the University of Alaska Fairbanks.

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